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Genetic studies of earliness and growth stages of Lycopersicon esculentum Mill. Li, Shin-Chai 1975

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GENETIC STUDIES OF EARLINESS AND GROWTH STAGES OF LYCOPERSICON ESCULENTUM MILL. BY SHIN-CHAI LI B.Sc., University of Taiwan, 1965 M.Sc., University of British Columbia, 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOGT'OR OF PHILOSOPHY in the Department of Plant Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA MARCH 1975 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada i i ABSTRACT I t i s desirable to develop tomato C Lycopersicon esculeritum M i l l . ) c u l t i v a r s which have the char a c t e r i s t i c s of earliness t o f i t the r e l a t i v e l y short and cool growing season i n Canada. Earliness was studied by p a r t i -t ioning the l i f e cycle of the tomato plant into 7 component growth stages and using these as a basis f o r attempts to recombine quantitative genes which control the earliness of d i f f e r e n t stages from d i f f e r e n t parents to obtain progeny e a r l i e r than both parents. The mode of inheritance of the earliness i n the 7 growth component stages was studied with 3 approaches. 'First, a complete d i a l l e l cross experiments'' used 3 parental c u l t i v a r s : Bonny Best, Immur P r i o r Beta and Cold Set. The progenies were grown under 2 temperature regimes (17.0-21.0°C and 10.0-13.0°C). The data f o r days required f o r each stage were analyzed f i r s t by the Hayman and Jinks method which estimated the following 4 genetic parameters; v a r i a t i o n due to differences i n additive and donrinant gene action; asymmetry of pos i t i v e and negative effects of genes; r e l a t i v e frequencies of dominant and recessive a l l e l e s ; and 5 genetic estimators: average degree of donrinance; proportion of dominant and recessive a l l e l e s ; r a t i o of the t o t a l numbers of dominant to recessive genes i n the parents; number of ef f e c t i v e factors which exhi b i t some degree of dativinance and the h e r i t a b i l i t y . The calculated genetic parameters and estimators d i f f e r e d i n the 2 tenperature regimes in d i c a t i n g there could be differences i n gene action such as overdominant instead of p a r t i a l dominant gene action depending on i i i the temperature conditions. There were differences i n h e r i t a b i l i t i e s f o r the component stages, and some of the longer stages had p o t e n t i a l l y useful high h e r i t a b i l i t i e s . The data were also analyzed by the G r i f f i n g method which estimated the general combining a b i l i t y and s p e c i f i c combining a b i l i t y . The analyses showed that both the additive and dominant gene action had s i g n i f i c a n t effects i n most of the component stages, and i n most cases, the additive variance was larger than the dominant variance. The second approach employed re c i p r o c a l cross experiments with 2 parental c u l t i v a r s , Bonny Best and Immur P r i o r Beta, and t h e i r r e c i p r o c a l hybrids under the 2 temperature regimes i n greenhouses and growth chambers. The nuclear and/or cytoplasmic effect on the 7 growth component stages, net photosynthesis rate and leaf area were studied. There was some evidence that cytoplasmic effects were r e l a t i v e l y important f o r some of these c h a r a c t e r i s t i c s , and these effects were more noticeable i n the cool regime. In the t h i r d approach, f i e l d selection experiments on the ,earliness of 2 major stages were commenced i n the F^ of Bonny Best and Immur P r i o r Beta re c i p r o c a l cross populations. The mean values f o r both stages i n the F^ r e c i -procal populations were e a r l i e r than the 2 o r i g i n a l parents indicating recombination of genes f o r earliness from parental c u l t i v a r s . These r e s u l t s indicate that the methods which were used i n these studies are a fea s i b l e way to increase the quantitative c h a r a c t e r i s t i c of earliness i n the tomato. i v TABLE OF CONTENTS page-INTRODUCTION ' • 1 LITERATURE REVIEW ...... .... • • . 3 A. D i a l l e l Crosses • 3 B. 'Reciprocal Crosses ... 5 C. Selection In Plant Breeding . • 7 D. Growth Component Stages And Temperature Effects •. 10 E. Genetic Analysis Of Growth And Earliness Of Tomato 26 MATERIALS AND METHODS ................... • • ... 29 MATERIALS • . ' ' • • 29 METHODS . ............ 31 A. Greenhouse Experiments 31 '.B.- Growth Chamber Experiments 33 C. F i e l d Experiments 31+ STATISTICAL METHODS • 37 A. Analyses Of Data From The D i a l l e l Crosses 37 B. Analyses Of Data From The Reciprocal Crosses • 42 C. Analyses Of. Data From The F i e l d Experiments '. 44 EXPERIMENTAL RESULTS .... 45 D i a l l e l Cross Experiments 45 Reciprocal Cross Experiments 88 F i e l d Experiments 99 DISCUSSION .- ........ '. -106 D i a l l e l Cross Experiments 106 Reciprocal Cross Experiments 117 F i e l d Experiments .; ..120 SUMMARY ' ' 124 LITERATURE CITED • .• 127 APPENDIX. . .... ' 144 V LIST OF TABLES Table P a§ e 38 1. The second degree stat i s t i c s for a d i a l l e l set (Mather and Jinks, 1971). .2. Analysis of variance for combining a b i l i t y giving expectation of mean squares for the assumption of a fixed model. M-1 3. Mean number of days required for each of the 7 stages i n the d i a l l e l cross tested i n warm and cool temperature.regimes i n greenhouse experiment I. 46 4. Calculated mean values of V and W for the 7 stages i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse experiment I. 47 5. Uniformity test of. W -V values by analyses of variance for 48 a l l the characters investigated i n the d i a l l e l cross experiments. 6. Correlation coefficient between parental values (y ) and W +V for a l l characters investigated i n the d i a l l e l cross experiment s. 52 7. Mean number of days required for stages 5 and 6 i n the d i a l l e l cross tested i n warm and cool regimes in greenhouse experiment I I . 60 60 8. Calculated mean values of V and W for stages 5 and 6 i n the d i a l l e l cross tested i n warm and cool regimes in greenhouse experiment I I . 9. Mean number of days required per.plastochron i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse experiment I I . 63 10. Calculated mean values of V and W for the days required per plastochron i n the d i a l l e l cross tested i n warm and cool regimes in greenhouse experiment I I . 63 11. Mean f r u i t weight (g) and f r u i t diameter (mm) i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse experiment I I . 65 12. Calculated mean values of V and W for the f r u i t weight and r r f r u i t diameter m the d i a l l e l cross tested m warm and cool regimes i n greenhouse experiment I I . 65 v i 69 69 73 73 13. Means and standard deviations f o r the d i a l l e l cross parameters derived from the data on days required f o r 7 growth stages i n the warm regime of the greenhouse experiment I . 14. The d i a l l e l cross estimators f o r the data of the warm regime of the greenhouse experiment I . 15. Means and standard deviations f o r the d i a l l e l cross parameters derived from the data on days required f o r 7 growth stages i n the cool regime of the .greenhouse experiment I . 16. The d i a l l e l cross estimators from the data of the cool regime of the greenhouse experiment I . 17. Means and standard deviations f o r the d i a l l e l cross parameters and estimators from warm and cool regimes i n greenhouse expe-riment I I . 77 18. Means and standard deviations f o r the d i a l l e l cross parameters and estimators from warm and cool.regimes•for days required per plastochron. 19. Means and standard deviations f o r the d i a l l e l cross parameters and estimators f o r warm and cool regimes f o r f r u i t weight and f r u i t diameter. 20. Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) combin-ing a b i l i t y f o r the growth component stages i n warm and cool regimes. 21. Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) combin-ing a b i l i t y f o r the stages 5 and 6 a f t e r hand-pollination treatment i n warm and cool regimes-. 22. Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) confin-ing a b i l i t y effects f o r days required per plastochron i n warm and cool regimes. 23. Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) combin-ing a b i l i t y effects f o r f r u i t weight and diameter i n warm and cool regimes. 24. Net photosynthesis rate and leaf area i n growth chamber expe-riment I i n warm regime. 25. Net photosynthesis rate and l e a f area i n growth chamber expe-riment I i n cool regime. 79 79 82 82 84 84 86 87 v i i 26. The non-orthognal comparisons f o r the seven growth component stages i n the recipr o c a l cross experiment I under warm and cool regimes. 89 27. The non-orthognal comparisons f o r the net photosynthesis rate i n the recipr o c a l cross experiment I I under warm and cool regimes. 91 28. The non-orthognal comparisons f o r the l e a f area i n the r e c i -procal cross experiment I I under warm and cool regimes. 96 29. Mean days required f o r stages A and C i n the f i e l d experiment I , part 1. 99 30. The mean number of days required f o r stages A and C i n the f i e l d experiment I , part 2. 100 31. Means, h e r i t a b i l i t y , selection progress and genetic progress i n F^ generations: 101 103 32. Mean days required f o r selections made f o r stages A and C i n the Fj- of the f i e l d experiment I I I . 33. Summary of the f i e l d experiments, mean days required f o r stage A. 105 34. Summary of the f i e l d experiments, mean days required f o r stage C. 105 LIST OF FIGURES Figure 1. (V ,W ) graph f o r stage 1, greenhouse experiment I warm regime. 2. CV ,W ) graph f o r stage 2, greenhouse experiment I warm regime. 3. (Vr,W ) graph f o r stage 3, greenhouse experiment I warm regime. 4. (V »W ) graph f o r stage 4, greenhouse experiment I warm regime. 5. CV ,W ) graph f o r stage 5, greenhouse experiment I warm regime. 6-i' (V ,W ) graph f o r stage 6, greenhouse experiment I warm regime. 7. CV ,W ) graph f o r stage 7, greenhouse experiment I warm regime. 8. CV »W ) graph f o r stage 1, greenhouse experiment I cool regime. .9. CV Wp) graph f o r stage 2, greenhouse experiment I cool regime. 10. CVr,Wr) graph f o r stage 3, greenhouse experiment I cool regime. 11. CV^jWp) graph f o r stage 4, greenhouse experiment I cool regime. 12. CV jW^) graph f o r stage 5, greenhouse,experiment I cool regime. 13. CV ,W ) graph f o r stage 6, greenhouse experiment I cool regime. 14. CV ,W^,) graph, f o r stage 7, greenhouse experiment I cool regime. (V ,W ) graph for stage 5, greenhouse experiemnt I I , warm regime. (V ,W ) graph for stage 6, greenhouse experiment I I , warm regime. (V ,W ) graph for stage 5, greenhouse experiment I I , cool regime'. (V ,W ) graph for stage 6, greenhouse experiment I I , cool regime. (V ,W ) graph for days required per plastochron,.greenhouse experiment I I , warm regime. (V ,W ) graph for days required per plastochron, greenhouse experiment I I , cool regime. CV ,Wr) graph for f r u i t weight, greenhouse experiment I I , warm regime. (V ,W ) graph for f r u i t weight,greenhouse experiment I I , cool regime.' CV ,W ) graph for fruit•:diameter, greenhouse experiment I I , warm regime. (V ,W ) graph for f r u i t diameter, greenhouse experiment I I , cool regime. Net. photosynthesis rate for each plastochron of four lines i n the warm regime. Net photosynthesis rate for each plastochron of four lines i n the cool regime. Leaf area at- each plastochron among the lines i n the warm regime. Leaf area at each plastochron among the lines i n the cool regime. X ACKNOWLEDGEMENT I wish to express my sincere thanks to the following persons, whose assistance i n the preparation of t h i s thesis has contributed, s i g n i f i c a n t l y to whatever merits i t may have. To Dr. C.A.Hornby, Associate Professor of Plant Science, who not only suggested.the topic f o r t h i s thesis but also spent many hours reviewing the manuscript. Moreover, during a l l phases of my. graduate study, he has given guidance and valuable personal assistance/ To Professors V.C.Brinks., K.Cole, G.W.Eaton, C.W.Roberts and V.C. Runeckles, Chairman of the thesis committee, thanks are expressed f o r taking the time to review t h i s work and f o r o f f e r i n g many h e l p f u l suggestions. F i n a l l y , t o my wife, Rose, whose love and confidence contributed to the timely completion of t h i s work. As a small token of my gratitude .for her devotion, I dedicate t h i s study to my. wife. INTRODUCTION The tomato (Lycopersicon esculentum .Mill.) i s one of the most important vegetable crops i n North America. This crop i s strongly thermoperiodic i n i t s environmental response (Went, 1957) and i s not w e l l adapted f o r short and frequently cool growing seasons i n Canada, therefore fa s t e r growing and e a r l i e r crops tolerant to cool temper-atures are a primary r e q u i s i t e i n the production of Canadian tomatoes. Breeding f o r increased earliness and cool temperature tolerance has been done f o r many years, but further improvement f o r both characteristics i s needed i n order to have an expanding tomato production program i n Canada. Powers et a l . (1950) studied tomato earliness by p a r t i t i o n -ing the l i f e cycle into 3 stages: a) f i r s t stage: seeding to f i r s t bloom; b) second stage: f i r s t bloom to f i r s t f r u i t set and c) t h i r d stage: f i r s t f r u i t set to f i r s t r i p e f r u i t . They proposed that re-combination of early stages could r e s u l t i n e a r l i e r c u l t i v a r s . These designated f i r s t and t h i r d stages were r e l a t i v e l y long and the genetic mechanisms which controlled these stages s t i l l need to be c l a r i f i e d . For t h i s study, the l i f e cycle of 3 c u l t i v a r s : Bonny Best, Immur P r i o r Beta and Cold Set was further partitioned i n t o 7 stages: 1) seeding to ge:mfeation;':2>) germination fo f i r s t true l e a f ; 3) f i r s t true l e a f to flower bud formation; M-) flower bud formation to f i r s t flower; 5) f i r s t flower to f i r s t f r u i t set; 6) f i r s t f r u i t set to color change; 7) color change to ripening. The objectives;;of the present experiments were 1) to evaluate 1 the ,7 growth component stages using the d i a l l e l ' cross technique to estimate gene action, h e r i t a b i l i t y and numbers of genes^ associated with each stage; 2) to use r e c i p r o c a l crosses to ascertain whether any differences could be attributed to cytoplasmic e f f e c t s ; 3) to contrast warm and cool temperature regimes inathe genetics studies i n the d i a l l e l and r e c i p r o c a l cross experiments and 4) to u t i l i z e the genetic knowledge i n a f i e l d selection program f o r earliness recombinations i n the t h i r d to f i f t h generations. 2 LITERATURE REVIEW A. D i a l l e l Crosses Jinks and Hayman (1953) and Hayman (1954), based on methods of Mather (1949), and using d i a l l e l crossing, showed how variances and covariances among pure l i n e s could be used to provide estimates of the o v e r a l l degree of dominance i n the parents, an estimate of h e r i t a b i l i t y and other genetic parameters. Accordingly, the d i a l l e l cross tech-nique has been widely used by plant breeders as a method f o r studying continuous v a r i a t i o n . Johnson (1963) pointed out that the d i a l l e l cross has 2 main advantages: a) experimentally, i t i s a systematic approach, and b) a n a l y t i c a l l y , i t has a genetic evaluation that i s .-, p r a c t i c a l f o r i d e n t i f y i n g the I'erossesiwith the best selection p o t e n t i a l i n early generations. G r i f f i n g (1956a) showed how the d i a l l e l analysis provides information about the variance of general combining a b i l i t y (a|).' and s p e c i f i c combining a b i l i t y (a*). G r i f f i n g (1956b) demonstrated that when a set of inbred l i n e s i s used i n a d i a l l e l crossing system, a genetic interpretation i n terms of quantitative inheritance i s made possible by the fact that the analysis i s r e a l l y a 'gamete' combining a b i l i t y analysis. Thus i n the d i a l l e l s t a t i s t i c a l analysis, the method may regard the genotypic e f f e c t of any i n d i v i d u a l as the summation of effects contributed by each gamete ( i . e . set of genes i n the gamete) and the inte r a c t i o n of gametes ( i . e . the interaction of the genes i n one gamete with those i n the other). Kempthorriie (1956) c r i t i c i z e d the Jinks-Hayman analysis on the basis that "the d i a l l e l cross must be interpreted i n terms of some population which has given r i s e to the homozygous parents i n inbreeding. I f such a population does not e x i s t then the whole analysis i s l i k e l y to lead nowhere, and also one may question the value of estimating genetic variance, un-less the estimated quantities are measures of the character-i s t i c of a d e f i n i t e population". Since the parents of s e l f - p o l l i n a t e d crops w i l l usually not have been derived by inbreeding from the d e f i n i t e population, Kempthorne e v i -dently considers that the Jinks-Hayman type of analysis of d i a l l e l crosses has l i t t l e p r a c t i c a l value as an a i d i n the improvement of s e l f - p o l l i n a t e d crops. Hayman (1957, 1958 and 1960) has considered these c r i t i c i s m s and has discussed some additional aspects of the theory by removing the r e s t r i c t i o n that the inbred l i n e s must be f i x e d . Gilbert (1958) has evaluated the d i a l l e l cross, and pointed out that t h i s technique does give more information than that obtained from the parents only: the d i a l l e l analysis provides additional information on dominance and recessive r e l a t i o n s , on genie i n t e r a c t i o n , and on probable linkage associations. The use of the d i a l l e l analysis to study quantitatively i n -herited characteristics of crops has received considerable attention during the l a s t 20 years. Many investigators have applied the Jinks-Hayman and/or G r i f f i n g approaches on various crops, including snap beans (Dickson, 1967); cotton (Verhalen et a l . , 1971; Al-Rarvi and Kohel, 1970); tobacco (Jinks, 1954; P o v i l a i t i s ' , :> 1966; Legg et a l . , 1970; Matzinger et a l . , 1971); ryegrass (Lewis, 1970); forage crops (England, 1968; Fejer, 1971); weeds (Williams, 1962); maize (Eberhart et a l . , 1964; Poneleit and Bauman, 1970; Rosenbrood and Ankrew, 1971); cabbage (Chiang, 1969); wheat ( A l l a r d , 1962; Kronstad and Foote, 1964; 4 Hsu and Sosulski, 1969; Bhatt, 1971); barley (Johnson and Aksel, 1959); f l a x (Shehata and Comstock, 1971); linseed (Ahand and Murty, 1969). In tomato, the d i a l l e l cross analysis has been applied to many c h a r a c t e r i s t i c s , such as locule number (Ahuja, 1968; Andrasfalvy, 1971); f r u i t s ize (Horner and Lana, 1956; K h e i r a l l a and Whittington, 1962; Peat, 1963; Khalf-Allah, 1970; Andrasfalvy,, 1971); y i e l d (Horner and Lana, 1956) and soluble so l i d s i n f r u i t (Stoner and Thompson, 1966). B. Reciprocal Crosses In h i s book "Extrachromoscmal Inheritance", Jinks (1964) defined reci p r o c a l crosses as crosses i n which the sources of male and female gametes are reversed. When parental l i n e s d i f f e r only by chromo-somal genes, i t i s generally unimportant whether these genes go i n t o male or female gametes; the progeny of rec i p r o c a l crosses between such parental/lines are genetically i d e n t i c a l . However, differences i n cer-t a i n quantitative characters between recipr o c a l crosses do a r i s e . Some examples of such characters are: o i l and f a t t y acid contents, grain y i e l d , maturity, plant and ear heights, and number of ears per plant i n maize (Bhat and Dhawan,197l; Garwood et a l . .,1970); flowering time and plant height i n Nicotiana r u s t i c a (Jinks et al.,1972); seed protein content i n soybeans (Singh and Hadley ,19.72); i n tomato, seed germination ( E l Hassan,1972); f r u i t s i z e (Halsted 1918, Cram 1952; Shumaker e t _ a l . .,1970); early maturity ( L i and Hornby, 1972; Shumaker et al.1970); early y i e l d (Driver,1937; Meyer and Peacock,1941; Moore and Qirrence,1950; Cram,1952;.Shumaker et al.,1970). The e a r l i e s t work on rec i p r o c a l breeding i n tomatoes was reported by Halsted (1918) on f r u i t s i z e . He concluded that i f a 5 small f r u i t c u l t i v a r was used as a female parent, the Yi produced smaller f r u i t , whereas i f the female parent was the l a r g e - f r u i t c u l t -i v a r , the F x produced larger .fruit., Moore and Currence (1950) studied 21 pairs of re c i p r o c a l hybrids i n tomatoes. They found that 6 pairs showed s i g n i f i c a n t differences between reciprocals i n early y i e l d , whereas f r u i t s ize and t o t a l y i e l d d i f f e r e d s i g n i f i c a n t l y i n thir t e e n and three pairs respectively. Driver (1937) and Meyer and Peacock (194-1) demonstrated differences between pairs of reciprocals f o r e a r l i -ness and t o t a l y i e l d i n Fi hybrid tomatoes. Cram (1952) claimed that the differences between tomato r e c i p r o c a l hybrids resulted from some maternal or cytoplasmic influence. E l Hassan (1972) reported that the re c i p r o c a l differences were found between Fi and F2 generations, i n tomato, f o r sprouting at 10.0°C.but not at 35.0°C. He concluded that the r e c i p r o c a l differences were attributable to the ^ contribution of the embryo genotype, maternal effects and i n t e r a c t i o n of maternal genotype and cytoplasmic e f f e c t s . L i and Hornby (1972) partitioned the tomato l i f e cycle i n t o 3 growth component stages under 2 d i f f e r e n t temperature regimes, they found that the days required to complete each of the growth component stages i n r e c i p r o c a l hybrids responded d i f f e r e n t l y . •P. Evidence f o r cytoplasmic inheritance has been reported f o r di f f e r e n t plants by many workers including Ashri (1964), Beale (1966), Granick (1965), Katsuo and Mizushima (1958), Koopmans (1959), Michaelis (1954) and Sager (1965). Bhat and'Dhawan (1970, 1971), Brown (1961), Fleming et a l . (I960) and Singh (1965, 1966), working with maize-y,;;have shown that the expression of some polygenically inherited t r a i t s may be governed by the cytoplasm. 6 Jinks et a l . (1972) reported that there are 2 kinds of d i f -ferences between re c i p r o c a l crosses, transient and persistent. These may be maternal or paternal effects. Differences i n the maternal environment can give r i s e to transient r e c i p r o c a l differences. Such differences are known i n the animal kingdom where they ' 'were traced to differences i n the maternal genotypes (Mather and Ji n k s , 1971). Per-sist e n t r e c i p r o c a l deferences; usually arise through unequal contrib-. utions of cytoplasmic determinants from the female and male gametes to the zygotes. Such differences are prevalent i n the plant kingdom. C. Selection In Plant Breeding The hi s t o r y of crops has been influencecl considerably by man's augmentation of selection. I t was understood that many crop characteristics were being modified by selection. Walker i n h i s 1969 review, stated that there were only three basic factors of selection even when the genetic s i t u a t i o n i s highly complex. F i r s t , selection operates because'^-some individuals are favoured i n reproduction at the expense of others; secondly, selection acts through heritable differences; and t h i r d l y , selection works_ upon va r i a t i o n already present i n the organism. Mather (1953) summarized the effects of selection on a population as being d i r e c t i o n a l s t a b i -l i z i n g or disruptive. Many characteristics such as y i e l d and earliness are easy to measure, but they are the products of interactions at both the genetic and environmental l e v e l s . These characteristics have been considered to be b a s i c a l l y controlled by genes with small e f f e c t s , which may be modified by environmental f l u c t u a t i o n and subsequently 7 the data lead to variable estimates of h e r i t a b i l i t y . Hazel and Lush (1942) showed.that selection f o r a t o t a l score i s much more e f f i c i e n t than selection f o r one t r a i t at a time. They also showed that selec-t i o n f o r several t r a i t s by using indepenent c u l l i n g l e v els f o r each i s more e f f i c i e n t than random selection f o r each t r a i t one at a time. In contrast, Mather (1960) proposed that the selection procedure begin with the p a r t i t i o n i n g of complex char a c t e r i s t i c s i n t o subunits (com-ponent analysis) and, with the use of biometrical genetics, modify the selection procedure as required. The best r e s u l t s from component analysis have been achieved when subunits act i n m u l t i p l i c a t i v e fashion; f o r instance, the y i e l d of the tomato plant can be expressed i n terms of f r u i t number and f r u i t s i z e ( G i l b e r t , 1961). S i m i l a r l y , Powers et a l . (1950) partitioned the tomato l i f e cycle i n t o 3 major component stages: 1) seeding to f i r s t flower, 2) f i r s t flower to f i r s t f r u i t set, and 3) f i r s t f r u i t set to f i r s t f r u i t ripening. They found l i t t l e evidence, that these subunits were determined by a s u f f i c i e n t l y small number of l o c i to permit simple Mendelian analysis. In reviewing t h e i r data, i t appeared that the biometrical t e s t sometimes showed that the subunits could be considered under more simple control than the complex characteristics of t o t a l y i e l d and earliness. Peirce and Currence (1959) reported on the r e s u l t s of selec-t i o n f o r 3 quantitative characters: earliness, y i e l d and f r u i t s i z e i n segregating populations of tomato plants. Their data showed1that-one generation of selection resulted i n a considerable gain i n f r u i t s i z e , a s i g n i f i c a n t increase i n y i e l d and l i t t l e change i n earliness. As expected the estimates of h e r i t a b i l i t y f o r earliness were low where-as the other two characteristics had higher h e r i t a b i l i t y values. 8 One major selection system developed to maintain a higher l e v e l of genetic v a r i a b i l i t y w i t h i n the breeding population i s re-current selection. This system has been proposed as a promising method f o r e f f e c t i n g stepwise changes i n gene frequency within a population as opposed to the development of inbred l i n e s which gave homozygosity under continuous s e l f - p o l l i n a t i o n . Comparative studies conducted by Comstock et a l . (1949), Lonquist and M c G i l l (1956), Sprague et a l . (1952) have demonstrated the superiority of recurrent selection over selection within s e l f - f e r t i l i z e d progenies. The rapid approach to-=~ ward homozygosity apparently did not allow adequate Opportunity f o r selection; therefore, A l l a r d (1960) suggested that some less intense form of inbreeding, such as sib-mating might a i d i n the selection of superior genotypes from a given foundation population. Khalf-Allah and Peirce (1964) applied t h i s method i n tomato and found that the progenies developed by sib-mating generally maintained higher genetic v a r i a b i l i t y f o r f r u i t s i z e , earliness and t o t a l y i e l d than did s e l f p o l l i n a t e d selections. Recurrent selection has also been applied to improve the s p e c i f i c combining a b i l i t y of breeding l i n e s i n many other crops, especially i n maize ( H u l l , 1945; Horner et a l . , 1972). The d i f f i c u l t y a r i s i n g from selection f o r a single t r a i t i s the genetic and cenvironmerital c o r r e l a t i o n with other t r a i t s , but t h i s can be p a r t i a l l y resolved by the use of a selection index. Such an index has been widely used by the animal breeders, but has been l i t t l e used by the plant breeders. Andrus and Bonn (1967) used an index i n a mass selection program with muskmelon. This index was a simple ' scoring method with equivalent economic weight attached to each char-acter. Plants with the largest t o t a l score or highest index were selected. Peirce (1968) reviewed selection procedures and the problems 9 involved. He noted that the estimates of parameters used to construct an-index are usually d i f f e r e n t f o r each c u l t i v a r population i n a breeding program, and these estimates, p a r t i c u l a r l y of genetic corre-l a t i o n s , are subject to considerable error. He states that* "The concept of selection by index i s a viable one and should not be discarded". He also stated that "An index i s p a r t i c u l a r l y suited t o those crops i n which value i s determined by r e a d i l y measureable attr i b u t e s . And f o r those measureable characters contributing to the balanced genotype, affected by d i f f i c u l t c orrelations, an index may help". Another aspect that must be considered by the plant breeders as affecting selection i s the magnitude of the genotype/environment interaction. A l l a r d (196M-) summarized t h i s problem as follows: "The genotype and environment i n t e r a c t i o n i s always a com-ponent of va r i a t i o n . Interactions, such as variety x lo c a t i o n , variety x treatment are frequently predictable, and one can usually breed plants that w i l l excel i n a s p e c i f i c envir-onment. The variety x year effects are not predictable, and the breeders must attempt to minimize the impact of such inte r a c t i o n by testiingy. v a r i e t i e s over a series of years and locations". Further emphasis on t h i s i n t e r a c t i o n was expressed by Cornst6ck and Mo l l (1963) as follows: "Because genetic facts are infe r r e d from observations on phenotype, because selection i s based on phenotype and becaused there .is a pot e n t i a l contribution of genotype and environment int e r a c t i o n effects on the phenotype of a l l quantitative characters; genotype x environment i s i n some way involved i n most problems of quantitative genetics and many problems of plant breeding, therefore, a l l of i t s poss-i b l e implications deserve attention." D. Growth Component Stages And Temperature Effects 1. Stage 1: From Seeding to Gernrination In e a r l i e r studies, v a r i a t i o n i n the rate of seed germination 10 at d i f f e r e n t temperatures has been observed in;;many vegetable crops. Kotowski (1926) reported that speed of germination f o r 17 d i f f e r e n t kinds of vegetables increased as the temperature rose. The optimum temperature f o r tomato was 18.0°C and the nuxiimum was between 11.0°C and 18.0°C. Went (1957) found the time required f o r tomato seed ger-mination depended greatly on temperature, and the lower the temper-ature then the longer the time required f o r gernrination. Whittington et a l . (1965) reported that time f o r germination showed a genetic com-ponent, but the relationships between d i f f e r e n t genotypes was much influenced by environmental factors. The eff e c t of temperature on seed germination was highly s i g n i f i c a n t , and the time required f o r germination being greatest at the lower temperatures. Whittington and F i e r l i n g e r (1972) indicated the inheritance of time to germination of tomato seed was largely additive and-closely related to seed s i z e . Pollack and Larson (1956) indicated that speed of tomato seed germ-in a t i o n depended primarily upon environmental f a c t o r s , and that with-i n one c u l t i v a r seed s i z e has l i t t l e or no effect. The existence of genetic differences i n the ca p a b i l i t y of tomato seed to germinate at low temperature has been mentioned by various investigators. Smith and M i l l e t t (1964) reported that s i g -n i f i c a n t differences were observed among 10 v a r i e t i e s at constant temperatures of 15.0°C and 10.0°C but not at 20.0°C. Kemp (1968) reported that the a b i l i t y of some tomato c u l t i v a r s , such as 'Earlinorth' and 'Rocket', to germinate at low temperatures may be inher i t e d ; and at 10.0°C or lower, the percentages of germination of a l l c u l t i v a r s was reduced s i g n i f i c a n t l y . Berry (1969) reported differences i n germ-ina t i o n response at 35.0°C and the existence of a heritable association 11 between high and lew temperature response. E l Hassan (1972) reported that sprouting at 10.0°C, germination percentage at 35.0°C, and rate of germination at 35.0°C are inherited characters and controlled by at least 3, 2 and 1 gene(s) respectively. He also reported a high corv r e l a t i o n between germination at low and high temperatures and the probable existence of 2 different genetic systems which are recombinable. Cannon et a l . (1973) reported the a b i l i t y of tomato l i n e PI 341988 to germinate at 10.09C i s controlled by a recessive gene ( l t g ) . E l Sayed andj©&pii (1973) pointed out that germination of tomato seed needs at least the accumulation of 160 d a i l y heat un i t s . They found the c h a r a c t e r i s t i c of germination at low temperature f o r the Fr::and F2 progenies was intermediate between t h e i r contrasting parents. In h e r i t -ance was found to be quantitative and an estimate of 24 gene pairs d i f f e r e n t i a t e d the parents f o r germination. There was strong evidence f o r additive gene action although dominance and epistasis were not ruled out. They also indicated that the same gene system appears to control emergence of seeds at both low (10.0°C) and high (20.0°C) temperatures with a h e r i t a b i l i t y of 25-40% and selection f o r emergence at low temperature could be achieved at high temperature. Phatak (1970) indicated that the seed from plants selected f o r normal germ-ina t i o n at 10.0°C night and 12.0°C day showed a d e f i n i t e improvement i n cold germinating a b i l i t y . 2. Stage 2: From Germination to F i r s t -Shme Leaf Appearance Variation i n growth of the seedling could be expected to be influenced by i n i t i a l embryo s i z e (Ashby 1930, 1937).- However, East (1936), Luckwill (1939) and Hatcher (1940) found that some tomatoes which showed heterosis f o r early seedling growth did not have any 12 apparent difference i n embryo s i z e and concluded that the s i z e of the embryo was not the index of heterosis. Whaley (1939) made a study of growth rates of the parents and hybrids i n two Lycopersicon species crosses showing heterosis. In both crosses the hybrids grew fas t e r than either parent i n the early post-embryonic stage, he also noted •. that heterosis was not always accompanied by the possession of a larger embryo i n the hybrid. In a second paper (1939) he presented evidence showing that there was no relationship either i n the embryo or during development, between the volume of the a p i c a l meristem and heterosis. Whittington et a l . (1965) using hybrids from L. esculentum and L.  pimpinellifolium found that the hybrid hypocotyl although i t s emergence was delayed by l a t e r germination, came to exceed i n length that of L. pimpinellifolium. Since hypocotyl extension i n tomatoes i n the dark i s by c e l l elongation rather than by c e l l d i v i s i o n , i t i s l i k e l y that t h i s r e s u l t i s due to an enhanced rate of extension of i n d i v i d u a l c e l l s i n the hybrids.• I t was thought that the s i g n i f i c a n t difference between the parent and hybrid was due to the greater c e l l number i n the hybrid hypocotyl. ' 3. Stage 3: From F i r s t True Leaf to Flower Bud Appearance (A) Leaf Development Throughout the h i s t o r y of research on crop plants many workers have sought to f i n d some observation or system of measurements that would accurately r e f l e c t the growth response caused by the environ-mental factors, f o r instance, flu c t u a t i o n of temperature has been evaluated i n various ways with respect to the effects on plant growth such as plant height, le a f area, phenological development, etc. As early as 1735, Reaumur attempted to correlate changes i n temperature 13 with plant development. Since then, the resultant correlations of growth and temperature data were developed. Went (1944, 1945), Verkerk (1955), Lewis (1953), Calvert 0-9SB", 1959) have demonstrated that the early development of the tomato i s affected by the temperature and l i g h t i n t e n s i t y during the f i r s t few weeks from germination. Calvert (1957, 1959) has shown that the number of leaves formed between the cotyledons and the''first inflorescence, increases with temperature but decreases with l i g h t i n t e n s i t y . Hussey (1963) reported that temper-ature had a greater e f f e c t on l e a f growth than on l e a f number; however, more leaves were formed before flowering at 25.0°C than at 15.0°C. He also observed the effects of high temperature i n delaying the en-largement of the apex and of increasing the number of leaves produced before flowering. The day and night temperature requirements f o r the tomato were iinVe^stigatedd by Went (1944) who^ ' • found that optimal growth occurs when the temperature during the dark period i s lower than that during the d a i l y l i g h t period. This kind of temperature response, he termed thermoperiodicity. Hussey (1965) indicated that the average day temp-erature affected l e a f growth one and h a l f times as much as night . temperature. To establish the process which controls the growth of tomato plants i s of some i n t e r e s t , because i t may a s s i s t the plant breeder i n choosing the d i r e c t i o n f o r developing improved -'cultivars • Went (1944) studied the correlation between various physiological processes and growth i n the tomato plant. He found the elongation rate of tomato stems decreased sharply during the day, and photosynthesis reached i t s optimum near 10,764 lux and was only s l i g h t l y lower at 18.0°C 14 than at 26.5°C, but was s i g n i f i c a n t l y lower at 8.0°C. Translocation of sugars was low at 26.5°C, and steadily increased as the temperature decreased to 8.0°C. (B) Plastochron In developmental studies one can usually r e l a t e only the simplest aspects of the developing organism or organ to time d i r e c t l y . The term 'plastochron' proposed by Askenasy (1880) has gained f a i r l y wide usage (Esau, 1953). She defined plastochron as:^ "The period between i n i t i a t i o n of successive leaves i n the shoot of a higher plant which appear p e r i o d i c a l l y " . When successive plastochrons are equal i n duration, the plastochron may be made to serve as the unit of a developmental scale. Ericksron and M i c n e l i n i (1957) defined a plastochron as the time i n -t e r v a l between i n i t i a t i o n of two successive leaves. Thus the plasto-chron might be more broadly defined as the i n t e r v a l between corres-ponding stages of development of successive leaves, and one might choose i n i t i a t i o n , maturity or any intermediate stage of development as the stage of reference. (C) Photosynthesis The y i e l d of each a g r i c u l t u r a l crop i s d i r e c t l y affected by the rate and production of photosynthesis. The production and the rate of photosynthesis are affected by the s o i l and c l i m a t i c condi-t i o n s , especially the l a t t e r ; f o r example, l i g h t (Porter, 1937; T a i l i n g , 1961; Hesketh and Moss, 1963; Hesketh and Baker, 1967; Peat, 1970; Scott et a l . , 1970); temperature (Wassink, 1945; Kramer andKerzlowski, 1960; Alberda, 1969; Hew et a l . , 1969; Machold, 1969; Treharne and Eagles, 1970); C0 2 concentration (Gaastra-a, 1962; Brun and Cooper, 15 1967; Bishop and Whittingham, 1968). In spite of the importance of photosynthesis, no serious attempt was made u n t i l recently to establish the genetic v a r i a b i l i t y i n photosynthetic e f f i c i e n c y among crop< plants. A plant breeder must understand thoroughly the masking effect of the various factors (both external and internal) regulating photosynthetic rates and in^.turn obscuring the genetic p o t e n t i a l i t y of t h i s character i n crop improve-ment programs. The evidence f o r genetic v a r i a b i l i t y of photosynthetic e f f i c i e n c y among species has been demonstrated i n numerous studies. Hesketh (1963) and Hiesey and Milner (1965) reported differences i n photosynthesis, amongg species such as Ricinus communis L., Helianthus  annus L., Zea mays L.,-^Dactylis glomerata L., Trifolium pratense L., Acer  saccharum Marsh., and Quercus rubra L. Differences f o r photosynthetic rate have been shown amonggcultivars within a species as ;inethe case of r i c e (Noguti, 1941); barley (Ekdahl, 1944); wheat (Asana and'.Kani, 1950); cotton (Muramoto et a l . , 1965); blueberry (Forsyth and H a l l , 1965); sugarcane ( I r v i n e , 1967); oats (Jennings and Shibles, 1968; Lawes and Treharne, 1971);;s©rghum (Eastin and S u l l i v a n , 1969); a l f a l f a (Eearoeei et a l . ,1969); bean (Wallace and Munger, 1966); maize (Duncan and Hesketh, 1968; Garg et a l . , 1969); tobacco ( Z e l i t c h and Day, 1973). In tomato, Stambera and Petrikova (1970) found a difference i n photosynthetic rate between determinate and indeterminate tomato vari e t i e s , and they also found that the high e f f i c i e n c y of the a s s i m i l -ative apparatus can be observed i n the period from the beginning of flowering t i l l the beginning of f r u i t formation. Breznev and Tagmazjav (1969) reported that i n the majority of hybrids, photosynthetic act-i v i t y during bud formation and flowering was higher than i n the 16 parental v a r i e t i e s and that the hybrids were superior i n y i e l d . Kirk and Tilney-Bassett (1967) indicated that there was the p o s s i b i l i t y of genetic control of formation of photosynthetic apparatus i n the plas-t i d , which apparently influenced the photosynthetic rate among the c u l t i v a r s . They also discussed a number of instances of mutations i n nuclear genes which might possibly be regulator genes, as f o r example, the green-flesh and the lutescent mutations i n tomato. Went (1957) pointed out that under normal f i e l d conditions young tomatoes probably lose less than 10 percent of t h e i r photosyn-thates i n r e s p i r a t i o n , the remaining 90% going i n t o the building of the tomato plant and f r u i t growth. Evans (1969) was of the opinion that photosynthetic rate constituted the primary l i m i t a t i o n to productivity i n tomato under most conditions. Donald (1962) expressed the opinion that plant breeders have been paying i n s u f f i c i e n t attention to photo-synthesis as a basic process affecting crop y i e l d . Also he pointed out that plant form or habit can affect photosynthetic gain. Moss (1969). indicated that breeding f o r photosynthetic e f f i c i e n c y requires the i d e n t i f i c a t i o n of desirable parental stocks. Non-genetic v a r i -a b i l i t y on photosynthetic measurements i s important. When measuring the photospiitihetdiG:: r a t e , one has to consider the environmental effects and t r y to control t h i s v a r i a t i o n . Kristoffersen (1963) pointed out that the net photosynthesis i n tomato was so greatly affected by en-vironmental f l u c t u a t i o n during the time periods used to make the measure-ments, that the net photosynthesis rate from such procedures were i n -e f f i c i e n t f o r i d e n t i f y i n g parental l i n e s with the genotypes f o r high net photosynthesis rates. 17-17 (D) Flower I n i t i a t i o n There are several reports about the influence of temperature and l i g h t on f l o r a l i n i t i a t i o n i n the tomato. Went (1941) reported : that the optima of normal day temperature and lower night temperature did not materially increase or decrease the number of flowers i n i t i -ated per inflorescence. Phatak (1966) compared two regimes, 15.5°C to 18.5°C and 18.5°C to 21.1°C during the period from the seedling to the appearance of the f i r s t inflorescence, and reported that the num-ber of flowers was s i g n i f i c a n t l y increased under the cooler regimes. Lewis (1959) reported that temperature was the main factor which af-fected the number of flowers i n a tomato inflorescence. He also i n -dicated that alternation of warm days and cool nights, and vice versa, as opposed to a uniform temperature, had no e f f e c t on flower number i n plants grown under natural l i g h t , but both temperature combinations had a depressing effect on flower /.production under a r t i f i c i a l l i g h t . Wittwer and Teubner (1956) and Calvert (1958) reported that e a r l i e s t flowering was i n i t i a t e d when the day and night temperatures were equal. Lake (1965) suggested that various plant processes such as vegetative growth, flower i n i t i a t i o n , f l o r a l growth and f r u i t growth may have dif f e r e n t temperature requirements. 4. Stage 4: From Flower Bud Appearance to F i r s t Flowering Wittwer and Aung (1969) reviewed the development of the tomato flower and indicated that a small protuberance of meristematic tissue develops from the pedicel of the preceding flower. The portion of t h i s pedicel posterior to the protuberance becomes part of the peduncle. The meristematic protuberance o r - a x i l -fortsbhelfirst flower of the c l u s t e r originates i n the a x i l of the le a f . The pedicel which 18 supports a single flower, as w e l l as the peduncle from which i t a r i s e s , i s composed of a rather thick cortex, a r i n g of vascular tissue and a central portion of p i t h tissue (Cooper, 192-7). Smith (1935) s i m i l a r l y observed that the protuberance of the f i r s t flower of the inflorescence arose i n the a x i l of the lea f . The succeeding flowers of the c l u s t e r each a r i s e from s i m i l a r protuberances which grow out from the pedicels of the preceding flower. There are reports about the environmental effects of temp-erature on flower development. Z i e l i n s k i (1948) reported that low temp-erature environment (7?28GCand 12.8°C) influenced perianth develop-ment i n the tomato, r e s u l t i n g i n f a s c i a t i o n of perianth components, and frequently i n adhesion of stamens to the c o r o l l a or calyx and and cohesion of the an t h e r i d i a l filaments. Rudimentary anther sacs with aborted pollen occurred frequently. Rick (1946) observed that under cool temperature, tomato flowers often drop without setting f r u i t , and one of the main reasons may be abortion of the p i s t i l . 5. Stage 5: From F i r s t Flower to F r u i t Set Although the days required f o r t h i s stage are r e l a t i v e l y few, there are several developmental processes which occur during t h i s stage. Besides the existence of viable pollen i n the anthers, there i s the need f o r transfer of pollen from the anthers to the stigma, pollen germination, pollen tube growth, f e r t i l i z a t i o n and early f r u i t development. A comprehensive study of factors a f f e c t i n g sporogenesis and the development of pollen grains was made by Hewlett (1936). Using c y t o l o g i c a l techniques he found that under conditions of severe car-bohydrate deficiency, sporogenous tissue i n some anthers f a i l e d to 19 reach meiotic d i v i s i o n . In addition to t h i s early e f f e c t , degener-ation of mature pollen grains was also a frequent occurrence (Calvert, 1964). Anthers which were subnormal i n s i z e and were not the normal deep yellow color invariably contained only s t e r i l e pollen grains. Went (1957) indicated that abnormal pollen was produced when temper-atures were lower than 13°C, and he considered t h i s to be the major factor causing unfruitfulness i n tomatoes grown at low night temper-atures. On the other hand, pollen can be produced normally, but may not be released from the anthers due to morphological abnormalities. Larson and Paur (1948) studied t h i s functional male-sterile tomato, and reported that the connate form of the petals resulted i n consid-erable c o n s t r i c t i o n of the anthers and tended to hold them i n close contact with the p i s t i l , thus preventing rupture of the stromium and the subsequent release of the pollen. The p o s i t i o n of the stigma within the anther tube and the i n t e r n a l dehiscence of the anthers favors a high degree of s e l f - p o l -l i n a t i o n . A number of workers have observed that with certain c u l t -ivars i n certain environments, the stigma may project beyond the open-ing of the anther tube, (White, 1918; Bouquet, 1919; Smith, 1935). More recently Williams CESSiDl) observed that both day length and temp-erature affected the rationof carpel length to stamen length. He also observed the degree of unfruitfulness l i k e l y to r e s u l t from s t i g -ma-'exsertion, f o r example, one c u l t i v a r which had a carpel length/,;'' stamen length r a t i o ^ o f 1.12 set only 16.2% of flowers, whereas another c u l t i v a r with a r a t i o n of 0:96 set 60% of the flowers. The time of dehiscence and the period during which the stigma remains receptive are c r i t i c a l factors i n the p o l l i n a t i o n and 20 f e r t i l i z a t i o n of inbreeding species such as the tomato. Smith (1935) stated that i n summer the c o r o l l a remained open and the stigma receptive f o r about 4 days. Judkins (1940) found the stigma to be receptive about 2 days before anthesis, and a period of 2-3 days usually elapsed be-tween p o l l i n a t i o n and f e r t i l i z a t i o n at normal greenhouse temperatures (16.0i'20.0°C). Koot and Ravestijn (1963) found the r e c e p t i v i t y of the stigma to be adversely affected by dry sunny weather, but i n d u l l humid weather l i t t l e pollen was liberated from the anthers. The r e c e p t i v i t y of the stigma and the a b i l i t y of pollen t o germinate appears to be strongly influenced by temperature. Exper-iments i n which pollen was germinated at 4- temperatures, namely 10.0°, 21.1°, 29.4° and 32.8°C were reported by Smith (1935) and Smith and Cochran (1935). They found that pollen remained in a c t i v e f o r several hours a f t e r being deposited on the stigma. At 21.1° and 29.4°C short tubes formed a f t e r 6 hours, but at 32.8°C only 0.1% of the pollen had germinated during the f i r s t 12 hours and only 3.9% a f t e r 84 hours. Germination was best at 29.4°C but only s l i g h t l y better than 21.1°C. Koot and Ravestijn (1963) assessed the degree of f e r t i l i z a t i o n by the percentage of pollen grains germinating on the stigma 2 hours a f t e r p o l l i n a t i o n . : : They found that both the degree and speed of germination were largely dependent on temperature. Dempsey (1969) reported tomato pollen germination occurred a f t e r 40 minutes at 35.0°C, and at 5.0°C the time was increased t o 20 hours. Hornby and Charles (1962) r e -ported "fe^t the need f o r a nanimum si z e of pollen application, and noted c u l t i v a r differences i n the minima. Afte r germination of the pollen grain, growth of the po l -l e n tube through the s t y l e i s the most important part of the sequence 21 of events during the progamic phase of f e r t i l i z a t i o n . Tube growth i s concerned with protein synthesis, formation of w a l l material, as w e l l as oriented growth toward the micropyle of the embryo sac. For external factors, temperature was found to have a marked effect on the genirination percentage of pollen as w e l l as on the rate of pollen • tube growth. The maximum rate of pollen tube growth occurred at 21.1°C with 29.4°, 10.0° and 32.0° ranging i n decreasing order (Smith and Cochran, 1935). P r e i l and Reimann-Philipp (1969) reported that the pollen tubes reached the ovary i n about 12 hours at 20.0-25.0°C and i n 48 hours at 10.0°C. Temporary low temperature (0°-2.0°C/15 hours) did not in j u r e the pollen tubes and they began to grow again when the temperature had r i s e n . Judkins (1940) reported the time involved i n pollen tube growth appears to increase during the f a l l and winter when l i g h t i s of low i n t e n s i t y . Dempsey (1969) stated that the ex-tensive pollen tube growth only occurred i n the 10.0-35.0°C range. At 37.0°C pollen tubes grew abnormally and l a t e r ceased growth while i n the s t y l e . He concluded that growth was inversely related to temp-erature because pollen tubes entered the micropyles 7 hours a f t e r p o l l i n a t i o n at 35.0°C but required 34 hours at 10.0°C. The sequence of events between p o l l i n a t i o n and*'fertilization was ca r e f u l l y observed and reported by Smith (1935). About 50 hours a f t e r pollen-.:reached the stigma, one of the male nuclei fused with the polar n u c l e i , the other fusing with the egg.. Af t e r f e r t i l i z a t i o n the zygote did not begin d i v i s i o n f o r 36 to 48 hours. The embryo sac greatly enlarged i n the meantime. The primary endosperm nucleus, began d i v i s i o n i n advance of the embryo. At 66 hours a f t e r p o l l i n -ation , when the zygote was s t i l l a single c e l l , the endosperm 22 consisted of 8 c e l l s with d e f i n i t e walls separating them. 6. Stage 6: From F i r s t F r u i t Set to F i r s t Change of F r u i t Color There has been considerable discussion and speculation on the general problem of the f r u i t s e t t i n g and the development of young f r u i t i n r e l a t i o n t o the growth of the plant and d i f f e r e n t factors of the environment. Shan'gina (1961) stated that r e l a t i v e l y poor f r u i t set on the lower truss of - the tomato may be attributed to the small storage reserves in- plants grown under the poor l i g h t conditions of early spring. Such- n u t r i t i o n a l deficiencies have been suggested as the possible cause of f a i l u r e or poor set f o r the f i r s t i n f l o r e s -censes to produce f r u i t i n tomato a f t e r transplanting (White, 1930; Rick, 1946; Leopold and Scott, 1952). Murneek (1939) pointed out that food reserves are of great importance i n the i n i t i a t i o n and devel-opment of the reproductive phase i n tomato plants. Regarding the environmental e f f e c t s , Went (1944) reported that i n the f i r s t and second c l u s t e r s , f r u i t set was abundant only when the night temperatures were between 10.0° and 20.0°C; and with lower or higher night temperatures, f r u i t i n g was reduced or even ab-sent. Lake (1965) studied the temperature ef f e c t on f r u i t s e t t i n g , and claimed the day temperature appeared more important than the night temperature. Robinson et a l . (1965) reported that cold temperature appeared to affect f r u i t setting of tomato primarily through i t s i n -fluence on microsporogenesis. They also reported that high temper-ature had a s i m i l a r effect.^ suggesting that the same genetic system determined f r u i t setting response to either high or low temperatures. This cool temperature effect on f r u i t set was also reported by Learner and Wittwer (1953), Calvert (1958), Wedding and Vines (1959), Schaible 23 (1962), Curme (1962) and Lake (.1967). ' Most v a r i e t i e s of tomatoes w i l l produce parthenocarpic f r u i t at a r e l a t i v e l y low temperature, but not at r e l a t i v e l y warm temper-ature. Osborne and Went (1953) found parthenocarpic f r u i t at a low temperature with a high l i g h t i n t e n s i t y . Daubeny (1955) found that poor pollen germination and/or growth may explain the parthenocarpic f r u i t produced by tomato cul±£\%>tBonny Best at the cool temperature (10.0° to 12.8°C) despite hand p o l l i n a t i o n . Leopold and Scott (1952) pointed out that tomato f r u i t set was strongly and quantitatively dependent upon the presence of mat-ure leaves. Darkened mature leaves were less e f f e c t i v e than l i g h t e r ones f o r promoting f r u i t set. . Agreement has not been reached as to the stage of develop-ment at which mitosis a c t u a l l y ceases i n the developing f r u i t . Smith and Cochran (1935) reported that c e l l d i v i s i o n proceeded a c t i v e l y i n the f r u i t f l e s h f o r approximately 2 weeks a f t e r p o l l i n a t i o n . Hough-t a l i n g (1935) as w e l l as Gustafson and Houghtaling (1935) concluded that f r u i t growth a f t e r p o l l i n a t i o n was a r e s u l t of c e l l enlargement only. MacArthur and Butler (1938) reported that ovary growth was e n t i r e l y by c e l l d i v i s i o n p r i o r to p o l l i n a t i o n , and that subsequent growth was c h i e f l y by c e l l expansion, c e l l d i v i s i o n being atfrninor factor that just s u f f i c e d to maintain the tissue containing non^ex-panding epidermal c e l l s . Groth (1910) had previously reported that young and mature f r u i t s contained the same number of epidermal c e l l s , and that mitosis played l i t t l e part i n the enlargement of the tomato f r u i t skin. Clendenning (1948) reported that growth of the f r u i t i n -cludes a phase of residual m i t o t i c a c t i v i t y that :;.pers'istsf-:c.for 24 approximately 1 week a f t e r setting. There i s a relationship between f r u i t p o s i t i o n within the truss and f r u i t growth. Beadle (1937) considering the f i r s t 6 f r u i t s i n the trusses of c u l t i v a r Kondine Red, found that the nearer the f r u i t was to the main stem then the shorter was the maturation period. Similar reports were made by Kidson and Stanton (1935), Kerr (1955) and Cooper (1959). There are also some relationships between growth rate, s i z e of f r u i t and other physiological characters. Cooper (1959) pointed out that f r u i t s which begin to swell r a p i d l y at the beginning of f r u i t development have a shorter maturation period than those f r u i t s which have a period of i n i t i a l lag before rapid growth begins. Gustafson and Stoldt (1936) pointed out that increasing the leaf area, can r e -s u l t i n the si z e of f r u i t being increased a f t e r the time of set t i n g . Clendenning (1942) reported that the growth of f r u i t was found to be associated with an absolute increase i n r e s p i r a t i o n crate. 7. Stage 7: From F i r s t Change i n F r u i t Color to F r u i t Ripening Color changes i n tomato f r u i t are the most obvious signs of ripening. These changes are primarily due to degradation of the chlor-ophylls and the synthesis of carotenoid pigments. Duggar (1913) and Sando (1920) reported that normal temperature and oxygen supply were the essential requirements f o r f r u i t ripening. High temperatures over 32.0°C and low temperatures under 10.0°C were reported to delay or even h a l t the ripening (Tomes, 1962; Pharr and Kattan, 1971; Walkof, 1962). Additional to the color changes i n ripening f r u i t , Pattersen (.1970) emphasized two major changes: 1) t e x t u r a l changes r e s u l t i n g 25 from environment and c u l t u r a l practices that a f f e c t c e l l morphology during growth; and 2) f l a v o r changes i n which there i s a perception of a combination of sweetness, a c i d i t y and astringency i n conjunction . with the odorous v o l a t i l e s . E. Genetic Analysis Of Growth And Earliness Of Tomato Investigations on si z e and shape i n the development of plant organs have given-further ins i g h t i n t o the more fundamental aspects of t h e i r inheritance. K h e i r a l l a and Whittington ( 1962) and Mallah et a l . (1970) pointed out that s i g n i f i c a n t differences i n growth rates were found between c u l t i v a r s and between the r e c i p r o c a l i n t e r - s p e c i f i c hybrids, and that l a t e r t h i s growth rate was found to be inherited ad-a d i t i v e l y with a large dominance component (Peat and whittington, 1 9 6 3 ) . K h e i r a l l a ( 1961) reported that delayed germination of L. frlnfeine-I-li- folium x L. esculentum r e l a t i v e to L. pimpinellifolium may allow a r e l a t i v e l y greater translocation of reserves to the shoot of the hy-b r i d . The growth rate of the hypocotyl i n t h i s hybrid was found to be higher f o r a l i m i t e d period p r i o r to emergence. This may be an explanation f o r the "undefined biochemical super i o r i t y " which Lewis Q!9j5}3>) suggested resulted i n the hybrid having a shorter "lag phase" i n the attainment of i t s growth rate. Luckwill (.MW) and K h e i r a l l and Whittington (1962) comparing hybrids and t h e i r parents reported that the hybrids had a larger le a f area which was related to a greater f r u i t y i e l d . Whaley (1939) pointed out that the leaves of hybrids were intermediate i n s i z e between par-ents and tended to be greater than the mean of the parents. Mallah et a l . (1970) reported that a dominant gene actioniwas found i n the 26 inheritance of le a f area, whereas f o r f r u i t s i z e both dominant and additive gene action were present. Whaley (1939) reported that the s i z e of flower i n tomato hybrids was intermediate between those of the parents. Somewhat sim-i l a r r esults were reported by Williams (1959), who found that none of the tomato hybrids exceeded the better parent f o r such char a c t e r i s t i c s as number of flowers, f r u i t s i z e and number of f r u i t s ; with the one exception of y i e l d per plant. The study of earliness led Powers and Eyi>h (194-1) to part-i t i o n the following 3 stages of the l i f e cycle, 1) seeding to f i r s t bloom; 2) f i r s t bloom to f i r s t f r u i t set and 3) f i r s t f r u i t set to f i r s t r i p e f r u i t . Later Powers et a l . (1950) concluded from the use of 2 parentadiscultivars and t h e i r hybrids that the f i r s t 2 stages' were each controlled by 3, and the t h i r d stage by t>2o major gene p a i r s . Honma et a l . (1963) reported that only 1 major gene p a i r controlled the f i r s t growth stage. Burdick (1954) reported that the time of flowering f o r hy-brids was approximately intermediate between the parents. Similar res u l t s were also reported by Williams (1959) and Young (1966). The opinions about the genetic mechanisms c o n t r o l l i n g com-ponent stages are varied. Corbeil (1965) found that early maturity genes were completely dominant to t h e i r l a t e phase a l l e l e s i n the second and t h i r d stages and p a r t i a l l y dominant i n the f i r s t stage:.' Peat and Whittington (1965) and Mallah et a l . (1970) found additive gene action with various degrees of dominant gene action f o r the f i r s t stage. Young (1966) claimed that dominant gene action f o r the f i r s t stage was lacking. Burdick (1954) stated the following: "The maturity genes of both parents appear to be expres-sing themselves, at d i f f e r e n t stages i n seme hybrids. This would support the view that dominance i s a r e l a t i v e phenomenon, depending on the stage of development and the environmental circumstances under which i t i s measured, and that the excellence of hybrids may be a t t r i b u t a b l e to the co-expression of the a l l e l e s from both parents, made possible by the existence of dominance along with ontogenetic and environment gradients." Burdick's idea was. supported by L i and Hornby (1972) who showed that certain hybrids exhibited earliness heterosis under a cool temper- ' \ ature environment (10.0°-12.0°C) but responded intermediately bet-ween parents under normal culture temperature conditions (19.0°-21.0°C). A number of workers have reported an association between earliness and certain other tomato characters. Alpat'ev (1957), Daubeny (1959) and Yeager and Meader (1937) reported that selection based on early flowering was the most e f f i c i e n t method i s o l a t i n g early tomato segregates. Bernier and Ferguson (1962) studied the relationships of developmental characters of the tomato with e a r l i -ness, and they found that the days to f i r s t flower (Stage 1) were negatively correlated with earliness (Stages 1, 2 and 3) f o r the c u l t i v a r s 'Imun P r i o r ' and 'Early Lethbridge'. Days required f o r Stage 3 were not correlated with earliness except f o r the c u l t i v a r s , E a r l i n o r t h , and 'Early Lethbridge', therefore they concluded that Stage 3 cannot be regarded as a good index of earliness. 28 MTERIALS AND METHODS MATERIALS Three true breeding tomato c u l t i v a r s which were used as parental l i n e s , and a l l possible combinations of t h e i r crosses were evaluated. The parental l i n e s were Bonny Best (B), Cold Set (C) and Immur P r i o r Beta ( I ) . They have the following h i s t o r y and character-i s t i c s . 1. Bonny Best (B) According to Boswell (1933) t h i s c u l t i v a r was introduced by the firm of Johnson and Stokes df Philadelphia, U.S.A. i n 1908. I t l i s very w e l l known on the North American continent. B has i n -determinate growth habit with round, fleshy and uniform colored f r u i t s . Boswell (1933) pointed out that maturation of B f r u i t was delayed ' considerably under cool temperatures or other unfavorable conditions. Ty p i c a l l y , there are 4 or 5 flowers per clus t e r with 2 or 3 f r u i t s being set per clust e r . This c u l t i v a r was used because i n the past years a considerable amount of research has been done, i n which t h i s popular c u l t i v a r was the t e s t plant. 2. Cold Set (C) I t i s a e r e l i t i v e l y new tomato c u l t i v a r f o r d i r e c t seeding, developed by Professor T. 0. Graham, at the University of Guelph, Ontario, Canada and released i n 1962. I t came from a cross between F i r e b a l l and F i l i p i n o #2. Both of C's parents are tolerant to Very warm 29 and cold temperal^jres. Young (1963) reported that i t i s resistant to cold temperature, and w i l l set f r u i t at a night temperature of 7.2°C. This cultivar can set i t s flowers under both cold and warm conditions. I t also has indeterminate growth, and uniformly colord f r u i t of medium size. • 3. Immur Prior Beta (I) The origin of this cultivar i s not known. Curme (1968) and Reynard (1968) believed that this cultivar was developed by Dr. A. K a l l i o , University of Alaska art Fairbanks, Alaska, U.S.A., how-ever Kallio (1968) said he obtained the seed i n 1951 from the Hort-icultrure Department of the University of North Dakota, U.S.A., and he also thought that this cultivar might have come from Europe. This cultivar has the potato leaf t r a i t . I t i s indeterminate i n growth habit, and i s very tolerant to low temp.er.atures (e.g. 10.0°C-12.0°C) for f r u i t set and vine growth. The f r u i t i s relatively small (60-90g) with flattened globe shape, somewhat angular with green shoulders. Dirikel (1966) stated that this cultivar i s one of the best for summer production i n heated glass houses i n the Alaska latitudes. The three parental lines were crossed i n a l l possible com-binations, thus there were six Fi hybrids. For convenience, these . six d i a l l e l cross hybrids were abbreviated with the female parent indicated f i r s t as follows: Bxl, (BI); IxB, (IB); BxC, (BC); CxB, (CB); Cxi, (CI); and IxC, (IC). 30 30 METHODS A. Greenhouse Experiments 1. Experiment I A d i a l l e l cross experiment employing the 3 parental and 6 Fi hybrids was conducted i n the winter of 1969!-1970 to observe growth stages under ' &2o temperature regimes. One greenhouse was kept i n the optimum range of 17.0°C-21.0°C and was considered to be the warm regime, i n contrast to the second house which was kept i n the 10.0°-13.0°C range and considered to be the cool regime. Seeds were sown on October 20 i n each of the 2 greenhouses. Seedlings were pricked out 2 weeks later and set i n 5 x 5 cm veneer bands i n f l a t s . Temperatures i n the 2 houses were recorded on ther-mographs throughout the experiment (Table 2 in Appendix). On Nov-ember 30, the plants were placed i n the s o i l beds i n 2 greenhouses. The plants were 50 cm apart within the row and 4-5 cm between the rows. Supplementary light was provided by 4 300-watt fluorescent tubes installed i n pairs over the s o i l beds to ensure a 14-hour photo-period. Pollination was allowed to occur naturally. A randomized block design was used with 4 blocks of 1-plant per plot for each of the 9 lines (see Table 1, Appendix). Earliness was recorded as the number of days required for each of the following: Stage 1: seeding to germination - germination was recorded when 50% of the t o t a l of 50 seeds per line had emerged and ex-panded their cotyledons to a horizontal level. Stage 2*:i\ germination to f i r s t true leaf emergence - which was 31 considered t o be when the f i r s t true l e a f had reached a length of 10mm. Stage 3: f i r s t true l e a f to flower bud emergence. Stage 4: flower bud emergence to f i r s t flowering - the flower was considered open when the c o r o l l a was bright yellow and had begun to r e f l e x . Stage 5: f i r s t flowering to f i r s t f r u i t set - which was considered to be when the f i r s t f r u i t had reached a diameter of 5mm. Stage 6: f i r s t f r u i t set to f r u i t changing color - when the f i r s t orange-pink color was shown at the blossom end. Stage 7: f r u i t changing color to f r u i t ripening - when the color hadd changed to red, the f r u i t was .considered to be r i p e . In Stage 3, the i n t e r v a l between f i r s t true l e a f t o flower bud emergence was subdivided i n t o plastochron units. The f i r s t plasto-chron was considered to be the age when the plant's f i r s t l e a f had reached the length of 10mm. When the second l e a f reached the'length of 10mm, i t was considered to be plastochron two, and so on. The number of days were also recorded f o r the in t e r v a l s between plasto-chrons. 2. Experiment I I The second experiment was done i n the winter of 1970-1971 and the purpose of t h i s experiment was to further the study of Stages 5 and 6 by using controlled p o l l i n a t i o n procedures to ensure that a l l the l i n e s had a uniform s t a r t i n g point f o r t h e i r f r u i t development. The flowers were emasculated 1 day before anthesis by taking away petals and anthers with a p a i r of tweezers. Pollen was collected 32 on microscope slides, and transferred to the stigmas with a needle. The date of hand pollination was considered as the f i r s t day of Stage 5. The second and t h i r d flower of the second cluster were used for this experiment. When the f r u i t reached 5mm diameter, i t was considered as the f i r s t day Stage 6. When ripe, the individual fruits were weighed and measured for diameter. The management regimes including temperature differentials for this experiment were similar to those i n the f i r s t experiment. Seeds of the 9 lines.were sown on Novemberr- 1, and the plants were set i n the s o i l beds on December 12. The same design was employed as i n Experiment I with a new randomization (see Table 3, Appendix). 3. Experiment I I I . This experiment used a larger population size but had to be limited to the two more promising parental cultivars, B and I, and their reciprocal hybrids. The management regimes including temp-erature'were similar to those i n the f i r s t 2 experiments. Seeds of the 4 lines B, I and their reciprocal hybrids were sown on Oct-ober 29, 1971. Plants were set on the s o i l beds on December 9 and a randomized block design was arranged with 10 blocks of the 4 lines. There was 1-plant per plot (see Table 5, Appendix). The same data were collected as i n Experiment I. B. Growth Chamber Experiments. 1. Experiment I This experiment was conducted to contrast the response of the plant materials at the cool temperature of 12.0°C with the more optimum one of 21.0°C. Seeds of 3 parental lines and their 6 d i a l l e l 33 hybrids f o r a t o t a l of 9 li n e s were sown on May 11, 1970. Seedlings were pricked out and set i n 7x7 cm p l a s t i c pots and placed i n growth chambers u n t i l the eighth plastochron stage was reached when the ex-periment was terminated. There was only one r e p l i c a t i o n per l i n e per plastochron. The plants were s h i f t e d around within the chambers every other day to minimize the environmental effects. Data were collected f o r plastochron ages s t a r t i n g from the 4th to 8th i n c l u s i v e l y . Plants were watered at 9:00 a.m. and net photosynthesis rate was measured at 10:30 a.m. An L/B Infrared Analyzer (Beckman model 15A) was used. The leaf area was measured i n an a i r f l o w planimeter. 2. Experiment I I This experiment used a larger population s i z e than i n Ex-periment I , but was l i m i t e d to the more promising parental c u l t i v a r s B and I , and t h e i r r e c i p r o c a l hybrids. Plants of the 4 l i n e s were arranged at random i n the growth chamber with 4 re p l i c a t i o n s f o r each plastochron. Seeds were sown on May 1, 1971 and the management was s i m i l a r to that i n Experiment I , and s i m i l a r data were collected on the 4th to 8th plastochrons i n c l u s i v e . C. F i e l d Experiments 1. Experiment I This experiment was conducted i n 2 parts i n f i e l d plots ,at The University of B r i t i s h Columbia i n the summer of 1971. The f i r s t part comprised B and I and t h e i r r e c i p r o c a l r crosses, f o r a t o t a l of 8 l i n e s (B, I , B l , .IB, BIxI, IBxI, BIxB, IBxB). Twelve plants per l i n e were used. The seeds were sown on A p r i l , 17,..and 34 transplanted to the f i e l d on May 10. This planting was about 1 to 2 weeks e a r l i e r than gardeners would set out plants, and i t was ex-pected that the plants would be under test to ascertain whether the plants could set f r u i t i n the less than optimum growing conditions. The data were recorded f o r t h i s and subsequent f i e l d ex-periments on i n d i v i d u a l plants as number of days required f o r each of the following stages: Stage A;, seeding to f i r s t flowering - the flower was considered open when the c o r o l l a was bright yellow and had begun to r e f l e x . Stage B: f i r s t flowering t o f i r s t f r u i t set - the f r u i t was consid-ered set when the diameter reached 5mm. Stage C: f i r s t f r u i t set to f r u i t ripening - a f r u i t was considered r i p e when the f r u i t color changed to red. SinceeStage B i s very short r e l a t i v e t o Stages A and C, i t was assumed that Stage B may not be as important as Stages A and C i n breeding f o r earliness, therefore Stage B was not considered f o r further study. The second part was used to observe the segregation of F 2 and F 3 from IB and BI recipr o c a l crosses, and ad d i t i o n a l l y to do selection among the F 3 plants. The selection was f o r earliness and tolerance of early spring cool temperatures. There were 6 and 11 plants selected i n the IB and BI l i n e s respectively. The selection c r i t e r i a i n t h i s 2nd part of the experiment were f o r segregates which were e a r l i e r than both parents, B and I , i n Stages, A cv and/or Stage C. 2. Experiment I I The selected plants from the F 3 generation of re c i p r o c a l 35 populations IB and BI were reproduced and evaluated. Thus there was the F^;. for 6 lines from IB selection and 11 lines from the BI selection plus two parents I and B, to give a t o t a l of 19 lines i n this experiment. Seeds were sown on March 30, 1972 and transplanted to the f i e l d on May 15. There were 5 plants per plot, 19 plots per block and to t a l of 5 blocks. The experimental design of the random-ized complete block i s shown i n Table 8 of the Appendix. 3. Experiment I I I This f i e l d experiment was conducted i n two parts. In the f i r s t part, seeds from the earliest 10% of the F i* of the IB and BI lines, which were pedigree selected i n Experiment I I , were used i n a simulated mass selection programme. Equal amounts of seed from, the earliest 15 plants selected i n the F i t of the IB line were mixed and a sample of the mixture was used to grow 125 plants which was the F 5 of the IB line. Similarly, seeds from 25 plants of the Fit of the BI line were mixed, and 250 plants were grown to provide the F 5 of the BI line. In the. second part, selected individual plants for e a r l i -ness were compared to the individual plants selected for lateness in the F i t generation. There were 6 plants from the F4 generation selected for earliness and 2 plants selected for lateness. These represented the extremes i n the F i t population. Seeds were sown on March 30, 1973 and transplanted to the f i e l d on May 11. Plants were arranged i n special blocks as shown i n Table 9 of the Appendix. Data for Stages A, B and C were collected as i n Experiment I. 36 STATTSTTCAL METHODS A. Analyses Of Data From The D i a l l e l Crosses Hayman (1954a; 1954b); Jinks (1954); Jinks and Hayman (1953) developed the analysis for the Fi generation of a d i a l l e l cross. The theory for their method can be divided into 2 parts. The f i r s t part proposes a p i c t o r i a l presentation i n which Jinks (1954) stated that "the covariance of array means on the common parent of the array gives the array covariance (W )". The Wr values for each array were plotted against the variance of the array (V ). In order for the basic assumptions for this analysis to be met, these points should l i e along a line of unit slope and within a parabola defined as ."Wr2= V x variance of parents". The position of the line gives an estimate of the degree of dominance. When the interception i s through the origin, complete dominance i s concluded. The intercep-tion above or below the origin indicates p a r t i a l dominance and over-dominance respectively. The-second part proposed a numerical analysis (Table 1) in which the variances and covariances available from the d i a l l e l table were defined i n terms of the components D, H l s H 2, F and E ( f i r s t designated by Mather, 1949), where D was the weighted com-ponent of variationndue to differences i n additive gene effects, Hj was the weighted components due to dominance, H 2 indicated the asymmetry of positive and negative effects of genes, F was a com-ponent due to the relative frequencies of dominant and recessive 37 TABLE 1. The second degree s t a t i s t i c s f o r a d i a l l e l set. (Mather and Jin k s , 1971) S t a t i s t i c s Model V . p D + E V r • h£) + J^ Hx -hF + 5/9 E W r %D -%F + 1/9:^ E V-r hp + -"*H2 + 5/81 E Hi = 4 V + V - 4 W - ^ 2±i-£ E r p r n H-2 = 4 V - M-V- + 2 ( n 2 u 1 ) E r r n z F = 2 V - 4 W - 2 ( n " 2 ) E p r n V r the variance of an array W r parent-offspring covariance of members of the same array W" r mean of Wr V r mean of Vj-V P variance of parents V-r the variance of array means E environment effect, derived from the block interactions of the family-.means (from analysis of variance of d i a l l e l table), i t has the same value for each block;V D the weighted component of variaffeionhdue to differences -in additive gene effects Hi the weighted components due to dominance Hjj. the asymmetry of positive and negative effects of genes F the relative frequencies of dominant and recessive alleles 38' a l l e l e s , (being p o s i t i v e when dominant a l l e l e s are more frequent, and negative when recessive a l l e l e s are the more frequent), and E was the component due to environmental error. Additional informa-t i o n may be gained: D<H1 , overdominance; D>Hi., p a r t i a l dominance. F>0, indicates that the parents carried an excess of dominant over recessive genes, also (H 1 /D) ' 2 indicates the average degree of dominance. I f t h i s value i s greater than one, there i s overdominance; i f equal to one, complete dominance; i f less than one, p a r t i a l dom-inance. Furthermore, H 2/4Hi i s an estimate of the average propor-t i o n of dominant and recessive a l l e l e s over a l l parental l i n e s . When, i t i s lower than i t s maximum value of 0 . 2 5 , the gene frequency of both dominant (u) and recessive (v) genes i s not equal at a l l l o c i . The function (4DH] ) 2+F/(4DHi ) 2-F estimates the r a t i o of the t o t a l number of dominant to recessive genes i n a l l parents. The value, h /H 2, i s an estimate of the number of genes which controls the character and exhibits dominance to some degree. The estimate of the heterozygote value h i s calculated as 2 (rn^i - m^), where m^ ?, i s .the 2 mean of a l l d i a l l e l (n ) progeny and m^ Q i s the mean of d i a l l e l (n) parents. The h e r i t a b i l i t y of the t r a i t i s calculated as HD/(kD+^Hi-!$F+E) (Crumpacker and A l l a r d , 1 9 6 2 ) . The theory underlying the p a r t i t i o n of the hereditary var-iance of the d i a l l e l crosses into the above components uses 6 assump-tions (Hayman, 1 9 54 ) : (.1) d i p l o i d segregation; ( 2 ) no differences between reciprocals; C3) independent action of n o n - a l l e l i c genes; (4 ) no multiple a l l e l i s m ; C5) homozygous parents; ( 6 ) genes i n -dependently dis t r i b u t e d between the parents. This method of analysis should only be applied i f these 39 underlying assumptions are met. When the data do not f u l f i l l any of the assumptions there w i l l be a deviation of the W V regression l i n e from a slope of 1, or an acurvature of the l i n e , or increase scat-: t e r i n g of points around the l i n e . When the graphed points give a l i n e of unit slope, the difference between Wr and'V w i l l be constant. A test of the assumptions i n the uniformity of W -V over arrays and experimental blocks. Lack of uniformity gives no information as to which assumption may have f a i l e d , although some ideas can be suggested from the W V.^  graph. The methods used and problems attacked by the d i a l l e l cross techniques have been diverse. One maj or system was developed by Jinks and Hayman (1953) who were concerned with gene l e v e l as men^. tioned previously. Another system developed by G r i f f i n g (1956) was concerned with gametlevjkevel known as general and s p e c i f i c combining a b i l i t y analysis (G.C.A. and S.C.A. respectively). For the purpose of comparison, both systems of s t a t i s t i c a l methods were used on the data of t h i s presentation. The terms general and s p e c i f i c combining a b i l i t y were or-i g i n a l l y defined by Sprague and Tatum (1942), but without a general-iz e d genetic interpretation of the combining a b i l i t y e f f e c t s . U n t i l 1956, G r i f f i n g used a d i a l l e l crossing system i n quantitative i n h e r i t -ance f o r the purpose- of estimating genetic parameters of the pop-ul a t i o n from which the inbreds were derived. He proposed two assump-tions: (1) the s i t u a t i o n i n which the parental l i n e s simply or the experimental material as a whole are assumed to be a random sample from some population about which inferences may be made (random model), and C2) the s i t u a t i o n i n which the li n e s are deliberately chosen and 40 TABLE 2. Analysis of variance f o r coirbining a b i l i t y giving expect-ation of mean squares f o r the assumption of a f i x e d model. source of variance d.f. sum of squares cmean expected mean 'square square G.C.A. p-l=2 S g M g a2 H ^Cp-2)C^ r]Eg? S.C.A. p(p-l)/2=3 S s *s ^ [ p T F 3 ) ] ^ S i j Reciprocal effects RError p(p-l)/2=3 m=27 S S r S S e M a % 2 e where S s=W?(X i j +X j.) 2 - C X . , + X t i ) * ( p . 1 } ( p . 2 ) x ; . s ^ z C x - . - x . . ) * Testing f o r o v e r a l l differences among the various classes of effects can be accomplished as follows: (1) to tes t G.C.A. effects use F ( p _ i ) , m " M g / M e (2) tostestCS^C.A. effects ^ : ^ ^ A 2 ^ % (3) to tes t f o r reciprocal effects use F p ( p _ 1 ) / 2 , m = M r / M e M I cannot be regarded as a random sample from any population ( f i x e d model). These two di f f e r e n t assumptions give r i s e to d i f f e r e n t es-timation problems and di f f e r e n t tests of hypotheses regarding com-bining a b i l i t y e f f e c t s . In t h i s presentation, only assumption (2) was considered',. (Table 2). The mathematical model f o r the combining a b i l i t y analysis i s assumed to be: x. . = u + g. + g. + s.. + r. . + 1/b I e. ., where x^j = i t h i n d i v i d u a l of j t h parental l i n e u = o v e r a l l population mean s i ^ g j ^ = t h e ^-.CA. effect f o r the i t h (jth) parent i , j = 1,.. .3 s.. = the S.C.A. effe c t f o r the cross between 1-' the i t h and j t h parents r-• = the re c i p r o c a l effect involving the re c i p -1-' r o c a l crosses between the i t h and j t h parents e.., = the environmental effect associated with the i j k t h i n d i v i d u a l observations b = the number of blocks, k=l,...4 B:' Analyses Of Data From Reciprocal Crosses Some of the data from the greenhouse (Experiment I I I ) and growth chamber (Experiment I I ) experiments were analyzed p a r t i t i o n i n g the variance as follows: The mathematical model f o r the re c i p r o c a l cross analysis i s assumed to be: y^j-'^u + 1^ + b^ + e^ .. where = j t h observation i n i t h l i n e - u = the o v e r a l l population mean 1^ = an ef f e c t due' to i t h l i n e , i=l,...4 42 tu = an effect due to j t h block, j=l,...10 e.. = an effect peculiar to j t h i n d i v i d u a l of i t h "L-' l i n e source ••of van' mce. d.f. Block ' 9 Line 3 Error 27 By 'the method outlined by Steel and Torrie (1960) •; : • the source of l i n e variance was further partitioned i n t o non-orthogonal compar-isons as follows: Line pedigree B I BI IB ' N/ic^euE Nucleus XX YY XY YX Cytoplasm Pi P 2 p l : P 2 No. of comparisons 1. B vs. I + 1 -1 o o 2. BI vs. IB o o +1 - 1 3. I vs'sIBIB- o +1 o -1 4. B vs. BI +1 o -1 o Following i s an outline of comparisons tested f o r s i g n i f -icance : 1. B vs. I: the inter-parental comparison 2. BI vs. IB: the Fj i n t r a - r e c i p r o c a l comparison. Since the reciprocals have the same nuclear comp-o s i t i o n , the differences between them w i l l be only due to cytoplasmic e f f e c t . 384. I vs. IB and B vs. BI: the maternals and t h e i r offspring comparisons. Since they have same cytoplasm, the differences w i l l be due to nuclear compositions. 43 C. Analyses Of Data From F i e l d Experiments Basi c a l l y the f i e l d experiments were designed with the pur-pose of determiriing the extent of v a r i a t i o n within each generation, and the selection progress was calculated i n the fourth generation. Data from a l l the f i e l d experiments were used to calculate the mean and standard deviation. In the f i e l d Experiment I I , selection pro-gress (AG) and genetic progress (crG) were calculated f o r both IB and BI populations based on the formulae a f t e r Falconer (1967) and Pirchner (1969): a - i hAG = i a h 2 S aG = AG/ih p where i = selection i n t e n s i t y (1.75) a = phenotypic v a r i a t i o n expressed i n standard P deviation h 2 = h e r i t a b i l i t y The estimate of h e r i t a b i l i t y was calculated using the variance components from the analysis of variance a f t e r Robinson et a l . (1949); and Grafius et a l . (1952). source mean expected variance d.f. . square mean square Line r-1 Mi CT2 + s o 2 e g Block s-1 M? CT2 + ra£ z e ;b Error (r-1)(s-1) M 3 o 2  . • _ e h 2 . v c V i V 2 - - a£ M3 h 2 = cT 2 :/(a 2 ; + = i - _ g g s Mx (note: h = square root of h e r i t a b i l i t y h 2 , and d i f f e r s from Hayman and Jinks 'h' genetic value of d i a l l e l analysis.) 44 EXPEPJJ^ENTAL RESULTS D i a l l e l Cross.?-- Experiments The data f o r the d i a l l e l cross experiments show the number of days required f o r each of the component growth stages as they occurred under the 2 temperature regimes, designated as warm and cool. The data were analyzed by the Jinks and Hayman (1953) and G r i f f ing (1956) methods. A. Hayman - Jinks Method (A) Greenhousel€b<periment I This experiment was concerned with the days required f o r plants to progress through 7 growth component stages i n 2 di f f e r e n t temperature regimes. The means f o r the 7 stages i n both warm and cool regimes are presented i n Table 3. The o r i g i n a l data are shown i n Tables 10 and l l of the Appendix. For each growth stage, d i a l l e l tables were set out f o r each of the four blocks, and W and V values calculated from them (Table r r 4); and the means were used to estimate the parameters and estimators. The differences, W -V , were obtained, and t h e i r uniformity was tested r r by analyses of variance. The uniformity t e s t of W -V f o r each of the characteristics r r i n Experiment I revealed that only Stage 3 i n warm, and Stage 6 i n cool showed s i g n i f i c a n t differences among arrays (Table 5), in d i c a t i n g that these 2 characteristics lack uniformity. The analyses gave no information as to which of the assumptions may have f a i l e d . I t was 45 TABLE 3. Mean number of days required for each of the 7 stages i n the d i a l l e l cross tested i n warm and cool temperature re-gimes i n greenhouse Experiment I. Female parent t Male + parent Stage Temperature warm cool warm cool warm cool 1 8.7 18.5 6.5 15.9 6.9 14.8 2 9.2 9.5 . 8.5 8.4 11.0 10.6 3 32.6 36.7 22.4 23.4 20.2 28.6 4 21.8 70.8 21.3 59.3 17.8 52.8 5 9.0 22.9 6.4 17.0 . 7.2 18.1 6 44.8 63.9 37.7 45.0 44.2 64.6 7 6.8 7.8 5.2 6.8 5.3 7.3 1 7.0 5.1 •7.3 16.3 6.3 15.7 2 9.1 8.6 9.0 9.5 10.0 10.8 3 21.5 23.3 17.3 20.1 18.5 19.2 4 • 27.3 51.3 18.5 58.0 17.8 47.5 5 6.0 8.8 6.5 20.0 6.7 18.8 6 40.7 42.4 35.9 . 48.9 39.8 58.1 7 5.1 7.6 5.0 7.5 5.0 9.6 1 7.2 16.4 6.4 15.8 7.4 15.8 2 8.7 8.9 10.2 11.2 9.2 12.4 3 21.8 76.1 18.8 18.8 22.1 26.7 4 20.8 52.8 17.0 59.3 22.8 51.8 5 •28.0. 18.0 6.2 - 17.9 7.4 18.3 6 45.9 64.8 39.8 58.8 48.1 53'. 0 7 5.6 7.1 5.0 8.8 6.4 ; 8.3 B B, Bonny Best I, Immur Prior Beta C, Cold Set 46 TABLE 4. Calculated mean values of V r and Wr f o r the 7 stages i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse Experiment I. V W W -V r r W +V - r r Array Stage warm cool- warm Temperature cool warm cool warm cool B C 1 1.5 3.8 0.9 2.6 -0.6 -1.2 2.4 6.4 2 0.5 0.7 0.1 0.7 -0.4 0.0 0.6 1.4 3 42.4 48.5 47.2 55.6 4.8 7.1 89.6 104.1 4 4.9 95.8 1.9 92.5 -3.0 -3"; 3 6.8 188.3 5 2.0. 7.9 -1.8 6.2 -0.2 -1.7 3.8 14.1 6 11.4 142.5 20.1 63.8 8.7 -78.7 31.5 206.3 7 0.8 2.4 0.9 1.7 -0.1 -0.7 1.7 4.1 1 0.3 2.7 -0.1 -0.6 -0.4 -1.3 0.2 0.1 2 0.6 1.6 0.1 1.9 -0.5 30.33 0.7 3.5 3 6.5 5.8 18.9 5.9 12.4 0.1 25.4 21.7 4 2.8 7.1 0.1 4.8 ~2> 7 -2.3 2.9 11.9 5 0.1 i l l . 2 -0.1 -0.5 -0.2 -1.7 0.1 0.7 6 5.6 55.8 14.5 -33.4 -8.9 -89.2 20.1 22.4 7 0.1 4.1 0.1 -0.3 0.0 -4.4 0.2 3.8 1 0.4 0.3 0.2 -0.1 -0.2 -0.4 0.6 0.2 2 0.3 2.0 -0.1 2.0 -0.4 0.0 0.2 4.0 3 4.6 22.8 7.5 33.1 2.9 10.3 12.1 55.9 4 7.9 2.0 6.5 4.6 -1.4 2.6 14.4 6.6 5 0.8 0.2 :.1.0 -0.4 0.2 -0.6 1.8 0.2 6 18.4 44.7 29.8 33.7 11.4 -10.0 48.2 78.4 7 0.1 0.8 0.1 -1.0 0.0 -1.8 0.2 -0.2 see Table 3 notation 47 TABLE 5. Urviformity t e s t of W^ -V values by analyses of variance f o r a l l the characters investigated i n the d i a l l e l cross experiments. T r a i t mean square Stage 1 i n warm 0.02 2 0.02 3 85.67* 4 0.63 5 0.33 6 0.05 7 0.01 Stage 1 i n cool 1.10 2 0.10 3 3.43 ^ 40.85 5 1.86 6 927.59* 7 1.33 days required per plastochron i n warm 0.02 days required per plastochron i n cool 0.01 days f^qlairgd 1 f o r Stage 5 i n warm 0.17 (p o l l i n a t i o n treatment) c . 0 i, c F .6 i n warm 3.45 days required f o r stage 5 i n cool 0.21 (p o l l i n a t i o n treatment) g ± n c q o 1 f r u i t weight i n warm 6477.58 f r u i t diameter i n warm 353.10 f r u i t weight i n cool 17016.20* f r u i t •diameternin cool 72.57 * s i g n i f i c a n t at the 5% l e v e l 48 recognized that sample error could have produced these s i g n i f i c a n t re-sults . Nevertheless, i t was advisable to proceed with the t o t a l anal-y s i s ; however, some caution should be attached to interpretation of re s u l t s . Ca) Graphical Interpretation of the genetic Parameters The regressions of W on are shown i n F i g . 1-4- and pro-vides the following information. Stage 1, warm: The regression c o e f f i c i e n t was 1.005 which was not s i g n i f i c a n t l y d i f f e r e n t from one. This showed a low l e v e l of epis-t a t i c gene action. Since the l i n e of uni t slope moved downward from o r i g i n to the r i g h t , then overdominance i s suggested. Jinks (1954) and Hayman (1954) indicated that the positions of the array points along the l i n e of regression of Wr on V r depend on the r e l a t i v e pro-portion of dominant and recessive a l l e l e s present i n the common par-ent of each array. Parents with a preponderance of dominant a l l e l e s w i l l have a low array variance and covariance, and w i l l l i e near the o r i g i n . On the other hand, parents with recessive a l l e l e s w i l l have a large array variance and covariance, and w i l l l i e at the opposite end of the regression l i n e . F i g . 1 indicated that the B parent had r e l a t i v e l y low, and C and I had r e l a t i v e l y high levels of dominance Hayman (1954) stated that: "A measure of association between the signs of dominant genes i s the correl a t i o n between parental s i z e and parental order of dominance. .The parental measurement, (y ), i s closely correlated with the number of p o s i t i v e homozygotes i n the parent while (W +V ) bears the same r e l a t i o n t o the number of recessive homozygotes." When the correl a t i o n between y^ and (W +V ) i s nearly one, the r e -cessive genes must be mostly p o s i t i v e ; when the correl a t i o n i s minus 49 Fig. 1 . (V ,W ) graph for Stage 1 . greenhouse Experiment I, warm regime. Fig. 2. (V ,W ) graph for Stage 2, greenhouse Experiment I, warm regime. Fig- (V ,W ) graph for Stage 3 greenhouse Experiment I, warm regime. r 5 W r ) graph for Stage 4. greenhouse Experiment I, warm regime. 50 one, the dominant genes are p o s i t i v e ; when the correla t i o n i s small, equal proportions of the dominant genes are po s i t i v e and negative i n t h e i r e f f e cts. As shown i n Table 6, t h i s c o r r e l a t i o n between -y and J r f o r Stage 1 warm was 0.99, and indicates that most of the re-cessive a l l e l e s i n the parents are acting i n the d i r e c t i o n of late-^ ness and the dominant a l l e l e s i n the di r e c t i o n of earliness. Stage 2, warm: The regression c o e f f i c i e n t was 0.35 which was s i g n i f -i c a n t l y d i f f e r e n t from both one and zero (Fig. 2). This value i n d i -cates that both dominant and additive genes must be operating. Since i s related to V by a s t r a i g h t ! regression l i n e , i t could be con-c l u d e d ' ^ ^ e p i s t a t i c gene action was minimal; and since the regression l i n e cuts the W axis downward from the o r i g i n , overdorninance was suggested. Although the positions of the array points B, I and C were close together, C i s closer t o the point of o r i g i n i n d i c a t i n g dominance over B and I. The correla t i o n between y and W +V i s neg-2p r r ative (Table 6), but the r e l a t i v e l y small value of -0.19 indicates p r a c t i c a l l y equal proportions of the dominant genes contribute to earliness (negative) or lateness ( p o s i t i v e ) . Stage 3, warm: As indicated before (Table 5) the analysis of v a r i -ance f o r w -V^ f a i l e d to prove uniformity among arrays, i n d i c a t i n g that one of the assumptions may not have been met; however, some j, idea of gene action may be gained from the W graph (F i g . 3). The regression c o e f f i c i e n t was o.92 which i s not s i g n i f i c a n t l y d i f f e r e n t from one and thus shows-'-absence of appreciable e p i s t a t i c gene action. The l i n e of unit slope cuts the axis upwards from the o r i g i n and thus indicates that p a r t i a l dominance i s functioning. From the graph, i t may be concluded that B was acting recessively and I and C dominantly. 51 TABLE 6. Correlation c o e f f i c i e n t between parental values (y ) and W +V f o r a l l characters investigated i n the d i a l l e l cross Stage 1 i n warm 0*99 2 -0-19 3 0.86 4 0.85 5 0.96 6 0.82 7 0.97 Stage 1 i n cool 0.93 2 0.49 3 -0v98 4 0.94 5 0.96 g o:;,99 7 0.78 days required per plastochron i n warm 0.52 days required per plastochron i n cool 0.93 days required f o r Stage 5 i n warm 0.84 ( p o l l u t i o n treatment) _ . n n Q y 6 i n warm 0.79 days required f o r Stage 5 i n cool 0.79 ( p o l l u t i o n treatment) g ± n c q q 1 q ^ q f r u i t weight i n warm 0.92 f r u i t diameter i n warm °- 5 3 f r u i t weight i n cool fruit-"diameter i n cool 0.83 52 The corre l a t i o n c o e f f i c i e n t between y r and W^ +V^  was 0.86 and because i t was p o s i t i v e and r e l a t i v e l y close to one, i t appears that the re-cessive a l l e l e s i n the parents are acting i n the d i r e c t i o n of lateness and the dominant a l l e l e s i n the d i r e c t i o n of earliness. Stage 4, warm: The regression c o e f f i c i e n t was 0.44 (F i g . 4) and was s i g n i f i c a n t l y d i f f e r e n t from both one and zero, which indicated that both dominant and additive genes were functioning. Since W i s r e -lated to by a st r a i g h t regression l i n e , i t could be concluded that n o n - a l l e l i c gene i n t e r a c t i o n was absent, and since the regression l i n e was downward r i g h t from the o r i g i n , then overdominance must be present. The positions of array points f o r B, I and C indicate i n -termediate, high and low levels of dfcnnnanee; respectively., The cor-r e l a t i o n between y^ and W^ +V was 0.85 which' was p o s i t i v e and high, hence providing evidence that recessive a l l e l e s are acting i n the d i r e c t i o n of lateness and the dominant a l l e l e s i n the opposite .' : - • di r e c t i o n . Stage 5, warm: The regression c o e f f i c i e n t was 0.94 ( F i g . 5) which was not s i g n i f i c a n t l y d i f f e r e n t from one, and indicated absence of e p i s t a t i c gene action. The l i n e of unit slope which almost goes through the o r i g i n , indicated p r a c t i c a l l y complete dominance. The array points show that B,C and I were acting at r e l a t i v e l y low, i n -termediate and high levels of dominance respectively. The correla-t i o n between y and W +V was 0.96 which was p o s i t i v e and high, and provides evidence that the recessive a l l e l e s i n the parents were act-ing i n the d i r e c t i o n of lateness. Stage 6, warm: The regression c o e f f i c i e n t was 0.98 (Fig. 6) which was not s i g n i f i c a n t l y d i f f e r e n t from one; therefore, absence of epis-t a t i c gene action was expected. The l i n e of unit slope which i s \ / 53 Fig. 7. CV^ ) graph f o r Stage 7, greenhouse Experiment I warm.; regime. 54 very close to the point of o r i g i n indicated p a r t i a l to complete dom-inance. The posi t i o n of the array points indicated that there was a sequence of C, B and I which ranged from low to high levels of dom-inance. The correlation c o e f f i c i e n t between y r and W^ +V^ was 0.82 which provides evidence that recessive genes were acting i n the d i r -ection of lateness. Stage 7, warm: The regression c o e f f i c i e n t was 0.97 (Fig. 7) which was not s i g n i f i c a n t l y d i f f e r e n t from unity which indicated an absence of e p i s t a t i c gene action. The regression l i n e cut the Wr axis upward l e f t from the o r i g i n and indicated p a r t i a l l y dominant gene action. The position of the array points showed that C and I had a r e l a t i v e l y high l e v e l of dominance compared with the low l e v e l f o r B. The cor-r e l a t i o n between y and W^ +V was 0.97, again provided evidence that most of the recessive a l l e l e s i n the parents must have been acting i n the di r e c t i o n of lateness. Stage 1, cool: The regression c o e f f i c i e n t was 0.71 (Fig. 8) which was not s i g n i f i c a n t l y d i f f e r e n t from one. This l i n e showed the same gene action and sequence of dominance as Stage 1 i n warm conditions. S i m i l a r l y the correlation c o e f f i c i e n t of 0.93 was es s e n t i a l l y the same as f o r Stage l,warm. Stage 2, cool: The regression c o e f f i c i e n t was 0.87 (Fig. 9) which was not s i g n i f i c a n t l y d i f f e r e n t from one^ indicating absence of epis-t a t i c gene action. The regression l i n e cuts the a x i s , l e f t and upward from the o r i g i n , i n d i c a t i n g p a r t i a l dominance Th e l e v e l of dominance f o r the parents ranged from low to high i n the order of C, I and B. I t was noted that f o r the f i r s t time B showed the high-est l e v e l of dominance. The correla t i o n between y^ and w r + ^ r w a s 55 Fig. 8. (Vr,Wr) g^aph for Stage 1, Fig. 9. (V^V^) graph for Stage 2, greenhouse Experiment -I, cool greenhouse Experiment I, cool regime. regime. 56 0.49 which was small, indicating there were equal proportions of the doniinant genes which were positive or negative. In other words, the dominant genes did not work entirely i n the direction of earliness, but about one half must have been contributing to lateness. Stage 3, cool: The regression coefficient was 0.98 (Fig. 10) i n -dicating the same gene action as above for Stage 2 i n cool. The se-quence for the level of dominance from low to liigh was B, C and I. The correlation coefficient between y and W +V was 0.98 indicating r r the recessive genes were acting i n the direction of lateness. Stage 4, cool: The regression coefficient between and was 0.96 (Fig. 11) which was the same as that for Stage 5, warm. Thus there was no appreciable epistatic gene action, but complete dominance was indicated. The graph shows that B had a very low level of dominance whereas C and I had a very high level. In other words, C and I w i l l be acting as dominant over B. The correlation coefficient between y and W^+V.^  was 0.94, which was high and positive indicating that dominant gene action was i n the direction of earliness. Stage 5, cool: The regression coefficient between Wr and V p was 0.89 (Fig. 12) and suggested the same gene action as for Stage 1, cool. The correlation coefficient between y cand;W+V was 0.96 indicating r r r that the recessive genes.were acting i n the direction of lateness. Stage 6, cool: As i n the case of Stage 3 i n warm, the analysis of variance failed to prove the uniformity of W^V^over arrays i n Stage 6 i n cool. Thus one of the assumptions for this d i a l l e l cross theory did not f i t . Nevertheless, some idea may s t i l l be gained from the W^ V^  graph (Fig. 13). The regression coefficient between and 57 12. (Vr,Wp) graph for Stage 5, greenhousk Experiment I cool regime Fig. 13. (V ,W ) graph for Stage 6, greenhouse Experiment I, cool regime. Fig. 14. (V , W ) graph for Stage 7, greenhouse Experiment I, cool regime. 58 was 0.69 which was s i g n i f i c a n t l y d i f f e r e n t from one. This coeffis' cient indicated that some e p i s t a t i c gene action and additive gene action may be present. I t can be seen that C and I were r e l a t i v e l y dominant over B. The correlation c o e f f i c i e n t between y and W +V JT r r was 0.99 in d i c a t i n g that the recessive genes were acting i n the d i r -ection of lateness. Stage 7, cool: The regression c o e f f i c i e n t between W and was 1.48 (Fig. 14) which was not s i g n i f i c a n t l y d i f f e r e n t fromone, in d i c a t i n g the same gene action as Stages 1 and 5 i n cool. The correla t i o n co-e f f i c i e n t was 0.78 from which i t may be concluded that the recessive genes were acting i n the d i r e c t i o n of lateness but may be acting ambidirectionally. (B) Greenhouse Experiment I I This experiment was mainly concerned with Stages 5 and 6, and to ensure f r u i t set potential,^pollen was transferred by hand with-i n the same c u l t i v a r . The mean values f o r both warm and cool regimes are presented i n Table 7. The o r i g i n a l data are shown i n Tables 9 and 10 of the Appendix. The design and analysis were the same as f o r Experiment I , but the management employed a r t i f i c i a l p o l l i n a t i o n to ensure a uniformity of f i r s t days, i . e . beginning of Stage 5. Table 7 n"eeds the comparison of the controlled p o l l i n a t i o n with the natural p o l l i n a t i o n treatment employed i n Experiment I..(.Table 3). The calculated W and V values are shown i n Table 8, the r r p i c t o r i a l regression l i n e s i n Figs. 15, 16, 17 and 18. The genetic information was e s s e n t i a l l y the same as Experiment I , i n other words, although these two experiments d i f f e r e d i n p o l l i n a t i o n methods, the gene action was s i m i l a r . 59 TABLE 7. Mean number of days required for Stages 5 and 6 i n the d i a l l e l cross tested i n warm and cool regimes i n green-house Experiment I I . Male f parent Female parent t B Stage Temperature warm cool warm cool warm cool B 5 8.0 6.6 6.3 7.9 6.8 7.9 6 40.0 58.6 35.3 53.8 42.5 62.9 I . 5 6.1 7.5 6.3 9.3 6.5 8.6 6 35.5 54.3 31.5 52.5 36.4 55.4 C 5 8.0 7.6 6.5 10.0 6.1 7.5 6 38.8 64.9 37.0 58.3 43.2 57.8 + see Table 3 notation TABLE 8. Calculated mean values of V and for Stages 5_and 6 in the d i a l l e l cross tested i n warm and cool regimes i n greenhouse Experiment I I . W W -V r r W +V r r Array Stage_ Temperature warm cool warm cool warm cool warm cool B J 5 0.9 0.5 0.8 0.6 -0.1 0.1 : 1.7 1.1 6 11.8 32.2 21.1 14.3 9.3 -17.9 32.9 46.5 I 5 0.3 1.2 0.1 0.9 -0.2 -0.3 0.4 2.1 6 10.9 7.8 20.6 5.6 0.7 -2.2 31.5 13.4 C 5 0.5 1.5 0.7 1.2 0.2 0.3 1.2 2.7 6 12.3 16.1 17.6 9.7 5.3 -6.4 29.9 25.8 + see Table 3 notation 60 1.5 F i g . 15. (V ,W ) graph f o r Stage 5, 10 2 0 F i g . 16. greenhouse Experiment I I , warm regime. (Vr,Wr) graph f o r Stage 6, greenhouse Experiment I I , warm regime. Days Required per Plastochron,' warm: Days required per plastochron i n both temperature regimes were measured from the 3rd to 8th plasto-chron (Table 9, plus Tables 11 and 12 of the Appendix). There was no s i g n i f i c a n t differences:.-, among arrays f o r the W -V^ uniformity t e s t (Table 5). The regression c o e f f i c i e n t between W^  and was 0.81 (Fig. 19) which was not s i g n i f i c a n t l y d i f f e r e n t from one, i n d i c a t i n g the absence of e p i s t a t i c gene action. The regression l i n e cut the o r i g i n of the axis meaning that there was complete dominance. The sequence f o r the l e v e l of dominance f o r the parents was C, B and I from low to high. The corre l a t i o n c o e f f i c i e n t between y r and W +V was 0.52 (Table 5) which was small, indicating equal proportions of the doniinant genes were pos i t i v e and. negative. Days Required per Plastochron ,-c®olr:: The regression c o e f f i c i e n t be-tween W and f o r the days required per plastochron i n the cool r e -gime was 0.91 (Fig. 20), which was not s i g n i f i c a n t l y d i f f e r e n t from one, indicating the absence of e p i s t a t i c gene action. The regression l i n e cut the W axis 1 downward from the o r i g i n meaning that there was overdominance. The sequence for the l e v e l of dominance from low to high was C, I and B. The corre l a t i o n c o e f f i c i e n t between y^ and VM-was 0.93 (Table 6>), which was p o s i t i v e and high in d i c a t i n g that the recessive genes were working i n the d i r e c t i o n of more days re-quired per plastochron (lateness). F r u i t Weight and F r u i t Diameter i n Both Regimes: The mean values f o r both temperature regimes are presented i n Table 11 and the o r i -g i n a l data are shown i n Table 13 of the Appendix. The uniformity . t e s t showed a s i m i l a r trend f o r the value of W -V between arrays r r • CTable 5), indicating the assumptions of the theory were met i n the 62 TABLE 9. Mean number of days required per plastochron i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse Experiment I I . : f  Female parent  Male parent warm B cool Temperature warm cool warm cool B I C 4.4 3.6 3.8 6.0 5.3 5.9 3.7 3.7 3.9 5.9 5.9 5.7. 4.1 4.1 4.1 5.4 5.7 6.3 see Table 3 notation TABLE 10. Calculated mean values of V r and Wr f o r the days required per plastochron i n the d i a l l e l cross tested i n warm and ; cool regimes i n greenhouse Experiment I I . Array V W W -V . r r W +V r r Temperature • warm cool ;.warm cool warm cool warm cool 0.13 0.05 0.12 0.04 - 0 . 0 1 - 0 . 0 1 0.25 0.09 I 0.12 0.05 0 .01 0.03 - 0 . 1 1 -0 .02 0.13 0.08 c 0.21 0.14 0.17 0.08 - 0 . 0 4 -0 .06 0.38 0.22 see Table 3 notation 63 • • 2 Fig. 21. CV ,W ) graph for f r u i t weight, 'Fig. 22. (V ,W ) graph for f r u i t greenhouse .'Experiment I I , diameter, greenhouse warm regime. 64 Experiment I I , warm regime. TABLE 11. Mean f r u i t weight (g) and f r u i t diameter (mm) i n the d i a l l e l cross tested i n warm and cool regimes i n green-house Experiment I I . Female parent  B I . C Male s Temperature parent 11'CU. L warm cool warm cool warm cool B d i . + 55.9 73.0 41.0 48.9 54.3 55.8 wt. 92.8 202.5 37.7 62.5 80.3 98.4 I d i . 42.0 45.5 33.9 37.5 42.4 47.8 wt. 39.0 52.4 21.2 28.5 40.5 55.3 C di . 57.1 56.3 40.5 46.1 52.1 52.9 wt. 99.6 91.5 37.8 51.5 76.8 76.9 +. di.v= f r u i t diameter T' wt. = f r u i t weaight TABLE 12. Calculated mean values of V r and W r .for the f r u i t weight and f r u i t diameter i n the d i a l l e l cross tested i n warm and cool regimes i n greenhouse Experiment I I . V W W -V r r W +V r r Array Trait Temperature warm cool warm cool warm cool warm cool B di.+ 79.3 179.8 91.9 238.8 12.6 59.0 171.2 418.6 Tf • wt. 1015.6 5767.4 1061.2 6810.9 46.4 1043.5 2076.8 12578.3 I d i . 29.2 34.7 57.8 85.3 28.6 50.6 87.0 120.0 wt. 138.6 272.7 426.9 1080.9 288.3 808.2 565.5 1353.6 C di . 73.6 24.8 98.8 79.1 25.2 54.3 172.4 103.9 wt. . 1009.0 . 453.3. .1242.5 1745,8 233.5 1292.5 2251.5 2199.1 = f r u i t diameter = f r u i t weight 65 present experiment for both f r u i t weight and diameter i n both the temperature regimes except the case of f r u i t weight i n cool which failed the uniformity test. The f r u i t weight i n warm had a regres-sion coefficient of 0.87 (Fig. 21) which was not significantly d i f -ferent from one, indicating the absence of epistatic gene action. The regression':,line cut the W axis upward from the origin pointing to p a r t i a l dominant gene action. The sequence for the level of dom-inance i s C, B and I from low to high, meaning I cMCfiivar-"i;s dominant over the C and B. The correlation coefficient between v„ and W+V was 0.92, which was positive and high, meaning the recessive genes operated i n the direction of heavier f r u i t weight. Fruit diameter i n warm had a regression coefficient of 0.85 (Fig. 22) which was not significantly different from one and hence the same gene action as that for the f r u i t weight i n warm. The correl-ation coefficient was 0.53 which was positive but not very high, i n -dicating that almost equal proportions of the dominant genes were positive or negative. Regarding f r u i t weight i n cool, although the differences between arrays for W -V failed to meet the uniformity test, nevertheless some genetic information may be gained from exam-ining Fig. 23, and noting that gene action was apparently similar to that for f r u i t weight i n warm. The only difference from warm regime results was the sequence for the level of dominance from low to high among the parents which was B, C and I rather than C, B and I as i n the warm regime. The correlation coefficient between y^ and W^ +V^  was 0.97, which was positive and high thus indicating that recessive genes were functioning i n the direction of heavier f r u i t weight. Fruit diameter i n cool had a regression coefficient of 1.04 66 Fig. 23. CVr,W ) graph for f r u i t weight, greenhouse "Experiment I I , cool regime. IOO 200 Vr Fig. 24.• CV ,W ) graph for f r u i t diameter, greenhouse Experiment I I , cool regime. 67 which was not s i g n i f i c a n t l y d i f f e r e n t from one (Fig. 24-), and ap-parently there was the same gene action as f o r f r u i t diameter i n warm. The l e v e l of dominance f o r parents was B, I and C from low to high. The correlation c o e f f i c i e n t was 0.83 indi c a t i n g the r e -cessive genes were operating i n the d i r e c t i o n of increased diameter : of the f r u i t . (b) Genetic Parameters and Estimators Considering the growth component stages i n both temperature regimes, the components of v a r i a t i o n and t h e i r proportions, upon which the graphical treatment was based, are given i n Tables 13 to 16. The proportions should r e f l e c t and i n part summarize the resu l t s of the graphical analysis. The genetic parameters and estimators f o r ': the experiment i n the warm regime as shown i n Tables l:3,cand"14 can be summarized f o r each stage as follows: Stage 1, warm: Exanuning the genetic parameters (Table 13) i t i s seen that TxHi , which indicated overdominance; and F<0, which i n -dicated the r e l a t i v e frequencies of recessive a l l e l e s were high. Considering the estimators (Table 14), the H2/4H1 value of 0.25, i n -dicated that the average proportion of dominant and recessive a l l e l e s was1 equal i n the parents; (Hi /D)'a, as an estimate of the average de-gree of dominance over a l l l o c i , and i n t h i s stage has a value of h 1.58, which being larger than one indicated overdominance; (4DHi) + F/ ( 4 D H i ) 2-F was 0.99, which was near enough to one, to imply that the r a t i o of the t o t a l number of dominant and recessive a l l e l e s i n the parents was equal; the h e r i t a b i l i t y was 0.2 which i s r e l a t i v e l y low; and the h 2/H 2 value was 1 .4 i n d i c a t i n g that at least one to 2 68 TABLE 13. Means and standard deviations for the d i a l l e l cross parameters derived from the data on days required for 7 growth stages i n the warm regime of the greenhouse Experiment I. Parameter  Stage D H 2 F 1 0.58±0.17 .1.45±":0."55 1.41±J0.52 -0.01±l0:.46 2 -0.05±0.10 1.51*00333 1.28±00;31 -0.11±00':27 3 60.69±5.88 30.03±18.69 26.89+17.63 25.65±15.67 4 4.47±2.50 13.16± 7.96 11.46± 7.51 2.68± 6.68 5 1.68±0.34 1.49± 1.07 1.38± 1.01 0.16± 0.90 6 40.78±4.20 • 3.66±13.35 3.41±12.59 • 0.89±11.19 7 0.89±0.20 0.43± 0.63 0.40± 0.60 0.33± 0.53 TABLE 14. The d i a l l e l cross estimators from the data of the warm regime of the greenhouse Experiment I.,-, (Table 13). Estimator Stage ( R V D ) 5 2 H2/4Hi (4BHi^+F ( W i ^ T h e r i t a b i l i t y h 2/H 2 1 1.58 0.25 0.99 0.21 1.4 2 5.61 0.21 0.65 -0.02 1.6 3 0.70 0;22 1.86 0.84 2.8 4 1.72- 0.22 1.42 0.15 2.0 5 & 0.94 0.23 1.11 0.39 • 3.6 6 0.30 0.23 1.08 0.83 3.6 7 0.69 • 0.24 1.74 0.63 4.0 69 genes controlling this stage exhibited some degree of dominance. Stage 2, warm: The values' of parameters (Table 13) indicated the same genetic information as from Stage 1, warm. Considering the es-timators, (H 7/D) 2 = 5.61 (Table 14), and being larger than one, means overdominance over a l l l o c i ; (Ufflx) +F/(4DH1)2-F was 0.65, which was less than one,,and indicated more recessive than dominant genes i n the parents. There was a very low and negative h e r i t a b i l i t y of -0.02 for this stage, and h 2/H 2 = 1.6 indicating at least 2 genes exhibited some degree of dominance. Stage 3, Warm: The summary of results was J>Ei (Table 13), which indicated partial•dominance; F>0 which indicated that the parents carried an excess of dominant over recessive genes; and Hi>H2, mean-ing unequal a l l e l e frequencies. The estimators showed H2/4Hi = 0.22-(Table 14) which indicated a highly asymmetrical, distribution of the dominant and recessive alleles i n the parents; (Hi/D) was 0.70, and being greater than zero but less than one, indicated pa r t i a l dominance; (4DH1):2,+F/(4DH1) 2-F was 1.86, and being larger than one, indicated more dominant than recessive genes controlled this stage. The herit-a b i l i t y was 0.84 indicating that highly inheritable genetic variation existed. A value of 2.8 for h 2/H 2, means that there were at least 3 genes exhibiting some degree of dominance. Stage 4, warm: The parameters (Table 13) showed D<H1, which indicated overxiominance, and F>0 showing that the parents carried more dominant , than recessive genes to affect this stage. The estimators (Table 14) show E2/mx = 0.22, and this low value indicated a highly asym-metrical distribution of the dominant and recessive alleles i n the parents'; also H 2 was smaller than , hence there were unequal 70 a l l e l e frequencies. (Hi/D) : was 1.72 which i s larger than one, therefore overdominance was present; and (4DH i) 2+F/(4DHi) 2-F was 1.4-2, which being larger than one, indicated an excess of dominant over recessive genes. The h e r i t a b i l i t y f o r t h i s stage was very low, only 0.15; and the h2/H2 value of 2.0 means that there were at least 2 genes showing some degree of dominance. Stage 5, warm: The parameters i n Table 13 showed fi>x\\ s l i g h t l y , which indicated p a r t i a l t o complete dominance, and F>0 which i n -dicated that the parents carried more dominant than recessive genes co n t r o l l i n g t h i s stage; and Hn>H2 , meaning unequal a l l e l e frequencies. The estimators show r\lkY\ - 0.23 (Table 14) which indicated a highly asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n \ the parents. (F^/D) 2 was 0.94, and being smaller than but very close to one, indicated that the estimate of the average degree of dominance over a l l l o c i was p a r t i a l but almost complete. (4DHi) 2+F/(4DHi) 2-F was 1.11, and being a l i t t l e larger than one, indicated a s l i g h t l y greater number of dominant over recessive genes affected Stage 5. The h e r i t a b i l i t y f o r t h i s stage was 0.39, and a value of 3.6 f o r '. _ h 2/H 2 means that there were at least 4 genes showing some degree of dominance. Stage 6, warm: The parameters from t h i s stage had the same trends as those f o r Stage 3, warm, therefore must have the same gene action. The estimators show H^AR^ =0.23 (Table 14), which indicated an asy-mmetrical d i s t r i b u t i o n ; (H^/D)^ was 0.30 and being larger than zero but smaller than one, indicated p a r t i a l dominance. (4BH1)^+F/(4DHj was 1.08, s l i g h t l y larger than one i n d i c a t i n g a s l i g h t l y greater number of dominant than recessive genes. The h e r i t a b i l i t y f o r t h i s 71 stage was very high, being 0.83; and the h 2/H 2 was 3.6 indi c a t i n g that at least 4 genes were exhi b i t i n g some degree of dominance. Stage 7, warm: The characteristics of the parameters f o r t h i s stage were s i m i l a r to those f o r Stage 6, warm. The estimators show n^AH^. 0.24" (Table 14), which indicated a highly asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s ' l i n the parents. (H^/D) = 0.69 which indicated p a r t i a l dominance; and (4DHi) 2+F/(4DHi) 2-F was 1.74 which being larger than one, indicated more dominant than recessive genes. The h e r i t a b i l i t y was 0.63 and h2/H2 was 4.0 indi c a t i n g that at least 4 genes showed some degree of dominance. Stage 1., cool: The parameters (Table 15) showed D<H!, which indicated overdominance; and F=1.75,- which being larger than zero indicated the parents carried more dominant than recessive genes which affected growth i n t h i s stage. Fh_>H2, hence there were unequal a l l e l e f r e -quencies.- H 2 A R i = 0.22 (Table 16) and t h i s low value indicated an asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the parents. (Hi/D) 2 =1.70, which i s larger than one and indicated overdominance. (4DHi) 2+F/(4DHi) 2-F = 1.84, which indicated more dominant than recessive genes affected t h i s growth stage. The h e r i -t a b i l i t y was 0.25 and the h 2/H 2 was 2.8 in d i c a t i n g that at least 3 genes were exhibiting some degree of dominance. Stage 2,, cool: E£: i s seen that D>H1 (Table 15), which indicated par-t i a l dominance; F=-0.95, and being less than zero indicated that re-l a t i v e frequencies of recessive a l l e l e s were higher than those f o r dominant a l l e l e s . H1>H2, thus the pos i t i v e and negative a l l e l e s f o r the l o c i c o n t r o l l i n g t h i s stage were not i n equal proportions. H^AH-L = 0.22 (Table 16), and such a low value indicated a highly 72 TABLE 15. Means and standard deviations for the d i a l l e l cross parameters derived from the data on days required for 7 growth stages i n the cool regime of the greenhouse Experiment I. Parameter Stage D H l H 2 F 1 1.74± 0.46 5.05± 1.48 4.54± 1.39 1.75± 1.24 2 2.34* 0.26 1.22± 0.83 1.07± 0.78 -0.95+ 0.70 3 68.28± 5.79 25.30±18.43 25.01±1738 -0.87± 1.55 4 92.53± 7.10 93.77+22.58 85.98±21.30 52.25±18.94 5 5.38± 0.58 10.30± 1.84 9.58± 1.73 3.94± 1.54 6 59.25±16.77 282.7 ±53.31 226.1 ±50.30 34.87±44.71 7 1.23± 0.43 5.72± 1.36 4.70± 1.28 2.26± 1.14 TABLE 16. The d i a l l e l cross estimators from the data of the cool regime of the greenhouse Experiment I., (Table 15).. Estimator Stage OVD) 1 5 H2/4Ri ^DH^+F (iHHi)'VF h e r i t a b i l i t y h 2/H 2 1 1.70. 0.22 1.84 0.25 2.8 2 0.72 0.22 0.56 0.37 2.4 3 . 0.61 0.25 0.98 0.64 5.6 4 1.01 0.22 1.78 0.65 3.6 5 1.38 0.23 1.72 0..42 3.6; 6 2.18 0.20 1.31 0.19 0.8 7 2.15 0.21 2.47 0.20 0.8 73 asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n 1^  the parents. (H^/D) 2 = 0.72, being smaller than one, indicated par-t i a l dominance; ( 4 D H 1) i 5+F/ ( 4 D H 1) J 5-F =0.56 and being smaller than one, implied more recessive than dominant genes were involved. The h e r i t a b i l i t y was 0.37 and h 2/H 2 was 2.4 which indicated at least 2 to 3 genes were exhibiting some degree of dominance. Stage 3, cool: The parameters f o r t h i s stage (Table- 15) showed the same trends as those f o r Stage 2, cool, and therefore both stages must have had the same gene action. H^AHj =0.25 (Table 16) and i n -dicated that the average proportion of dominant and recessive a l l e l s was equal i n the parents. (H^/D) 2 was 0.61 and, being less than one but more than zero, suggested p a r t i a l dominance i n action over a l l l o c i . (4DRi) 2+F/(4 D H i) 2-F = 0.98, which was near enough to one to imply that *here was an equal number of recessive and dominant genes involved. The h e r i t a b i l i t y was 0.64, and there were at least 6 genes exhibiting some degree of dominance. Stage 4, cool: The parameters f o r t h i s stage (Table 15) showed the same characteristics as those f o r Stage 1, cool, therefore both stages must have had the same gene action. The estimators (Table 16) showed Hj/4H2 = 0.22, a r e l a t i v e l y low value, which indicated a highly asy-mmetrical d i s t r i b u t i o n of donrinant and recessive a l l e l e s i n the parents. (Hi/D) 2 was 1.01, almost equal to one, thus i n d i c a t i n g that complete dominance was present. ( 4 D H i ) +F/ ( 4 D H i) 2-F = 1.78,- and being greater than one, indicated a greater number of dominant than recessive genes were involved. The h e r i t a b i l i t y was 0.65, and the h 2/H 2 was-3.6 implying that at least 4 genes showed some degree of dominance. 74 Stage 5, cool: The characteristics of the parameters f o r Stage 5, cool (Table 15) were s i m i l a r to those f o r Stage 4, cool, i n d i c a t i n g s i m i l a r gene action i n both stages. The estimators (Table 16) showed E2/kEi = 0.23, meaning a highly asymmetrical d i s t r i b u t i o n of the dom-inant and recessive a l l e l e s i n the parents; (Hr/D) 2 was 1.38, and being larger than one, implied overdominance; and (M-DHT) 2+F/(4DH!) 2-F was 1.72, which indicated that more dominant than recessive genes were affecting t h i s stage. The h e r i t a b i l i t y was 0.4-2, and the h 2/H 2 was 3.6 implying that at least 4 genes showed some degree of dominance. Stage 6, cool: Again the characteristics of the parameteis f o r Stage . 6, (Table 15) c o o l , were s i m i l a r to those Stage 4, c o o l , thus gene action must have been s i m i l a r i n Stages 4, 5 and 6, i n cool. Values i n Table 16 showed H^AR} = 0.20 and indicated unequal d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the parents; (R^/D) 2 = 2.18 which being larger than one, implied overdominance was present; and (4DHj) 2+F/(4DHi) 2-F was 1.31, and being larger than one, indicated more dominant than recessive genes affecting earliness of t h i s stage. The h e r i t a b i l i t y f o r t h i s stage was 0.19 and the h 2/H 2 was 0.8 imp-l y i n g that at least one gene was exh i b i t i n g some degree of dominance. Stage 7, cool: I t i s seen (Table-15) that D^Hj, which indicated over-dominance; F=2.26, and being larger than one, indicated the parents carried more dominant than recessive genes aff e c t i n g t h i s stage. Hi>H2 and also H^AHj = 0.21 (Table, 16) which indicated an asymmet-r i c a l d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the par-ents; (Hj/D) 2 =2.15, and being larger than one, indicated overdom-inance; and (4DHi) 2+F/(4DHi) 2-F was 2.47 which being larger than.one, 75 indicated a greater number of dominant than recessive genes involved. H e r i t a b i l i t y was 0.20 f o r t h i s stage, and the value of h 2/H 2 was 0.8 which indicated at least one gene exhibited some degree of dominance. (B) Greenhouse Experiment I I Greenhouse Experiment I I was concerned with the days r e -quired f o r plants t o progress through growth Stages 5 and 6 i n two . temperature regimes, and using a r t i f i c i a l p o l l i n a t i o n throughout the experiment. Stage 5, warm: The parameters f o r t h i s stage (Table 17) showed the same trends as those f o r greenhouse Experiment I , therefore both stages must have had the same gene action. H 2/4H T = 0.19 and i n -dicated an asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the parents; (H"i/D) 2 = 0.98, very close to one, indicated almost complete dominance. (4DH})2+F/(4DH!)2-F was 1.72 and being larger than one indicated more dominant than recessive genes affected earliness. The h e r i t a b i l i t y was 0.39, and at least one of the genes involved i n the earliness exhibited some degree of donunance. Stage 6, warm: Again the same gene action as i n Stage 6, warm, i n the greenhouse Experiment I i s shown by the characteristics of the parameters (Table 17). H 2/4Hi = 0.24, and t h i s very low value i n -dieates an asymmetrical d i s t r i b u t i o n ; (Hj/D) 2 = 0.18 and being larger than zero implied p a r t i a l dominance (4-DH! )Js+F/(4DH1 )^-F = 1.72, and being larger than one, indicated more dominant than recessive genes were involved. The h e r i t a b i l i t y was the high value of 0.77, and the h 2/H 2 was 4.80 which indicated at least 5 genes exhibited some degree of dominance. 76 TABLE 17. Means and standard deviations f o r the d i a l l e l cross parameters and estimators from warm and cool regimes i n greenhouse Experiment I I . Temperature Stage Parameter/Estimator warm cool D 1.06*4 0.18 1.85-±0.44 H! 1.02**0.58 1.47'-±1.39 H 2 0.79t±0.55 1.20 ±1.31 F •0 J5!5±0.49 -0.10 ±1.17 5 (Hi 0.98 • 1.04 (Uffll^+F/C+ffli^-F 0.19 1.72 0.20 0.93 h e r i t a b i l i t y 0.39 0.27 • h2/H 2 0.80 0.40 D 40.16±11.46 9Q03± 5il2; H l H 2 -1.29± 3.64 34,78±16.27 -1.35±33v43 28,14±15.35 F 3.81± 3.05 -14.78±13.64 6 (Hj/D)1'1 0.18 1.96 H 2 / 4 H l 1 v (4IH1)^+F/(l4ffl1)^-F 0.24 • 1.72 0.20 0.41 h e r i t a b i l i t y 0.77 0.12 h2/H 2 4.80 0.40 77 Stage 5, cool: The parameters f o r t h i s stage show the same trends as those f o r Stage 5 i n greenhouse Experiment I ; thus the same gene 1, action must have been present. (Hj/D) 2|?,= ;1.04 (Table 17), and being larger than one, indicated overdominance; and r^AR^ = 0.20, and t h i s low value indicated an asymmetrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the parents. (M-DH^  )^+F/(4-DHj )^-F = .0.93, which implied almost equal numbers of dominant and recessive a l l e l e s among parents, and the recessive genes had a l i t t l e higher frequency than the dominant. The h e r i t a b i l i t y was 0.27 and at least one gene showed some degree of dominance. Stage 6, cool: The parameters f o r t h i s stage (Table 17) show the same trends as the greenhouse Experiment I Stages 6, thus the same gene action was present. (R^/D) 2 = 1.96, which indicated overdom-inance; H 2/4Hi = 0.20 and t h i s low value indicated a highly asymme-t r i c a l d i s t r i b u t i o n of the dominant and recessive a l l e l e s . (4DH}) 2 +F/(4DH1)1^-F = 0.41, and being smaller than-one, indicated more recessive than dominant genes aff e c t i n g earliness. The h e r i t a b i l i t y was 0..12, and at least one gene showed some degree of donrinance. Days Required per Plastochron i n Both Temperature Regimes In the warm regime the parameters (Table 18) show D was almost equal t o H} indi c a t i n g complete dominance; Hj <H2, therefore there were not equal proportions of positive and negative a l l e l e s i n the parents, and F<0, meaning that the r e l a t i v e frequencies of re-cessive a l l e l e s were high. (Hi/D) 2 i s 0.92 which i s very near to one and means almost complete dominance was present. H 2/4Hi = 0.19, and t h i s low value indicated an asymmetrical d i s t r i b u t i o n of the 78 TABLE 18. Means and standard deviations for the d i a l l e l cross parameters and estimators from warm and cool regimes for days required per plastochron. Parameter and Estimator Temperature warm cool D -0.15±0.08 0.01±0.02 . Hi -0.13±0.24 0.16±0.06 H 2 -0.10±0.23 0.16±0.06 F -0.20±0.20 0.03±0.05 (Hi/D)^ • 0.92 4.90 0.19 0.26 (M-DHi^+'F/CMffii^-F 0.15 0.38 her i t a b i l i t y -0.16 0.02 h 2/H 2 2.0 5.6 TABLE 19: Means and standard deviations for the d i a l l e l cross par-ameters and estimators from warm and cool regimes for fr u i t weight and f r u i t diameter. Temperature Parameter« warm Cool and Estimator:.- f r u i t f r u i t f r u i t f r u i t weight diameter weight diameter D 1423.9±246.4 130.4±21.0 7992.5±449211 315.2+19.0 Hi 334.1+783.6 7.9± 6.7 3583.6±1564.9 84.0±60.4 H 2 264.5±739.3 4.-7± 6.3 3196.5±1476.4 73.0±57.0 F -459.3±657.1 -40.H55.9 3150.9±1312.3 102.7±50.7 OVD)*2 0.48 - 0.25 0.67 0.52 H2/4H! 0.20 0.15 0.22 0.22 (MDHi^+F/CMffli^-F 0.50 0.23 1.83 1.92 her i t a b i l i t y 0.44 0.48 0.91 0.97 h 2/H 2 0.4 8.8 2.8 2.-0 79 dominant and recessive a l l e l e s . (4-DHj) 2+F/(4DH1) 2-F = 0.15, and since t h i s value was less than one, there must have been more recessive than doniinant genes involved. The h e r i t a b i l i t y was -0.16 and at least 2 genes showed some degree of dominance. In the cool regime D<H1 (Table 18), ind i c a t i n g overdominance;; Hj was equal to H 2, meaning that p o s i t i v e and negative genes were present i n equal numbers; and F<0, which indicated r e l a t i v e frequencies of recessive a l l e l e s were high. (R^/D) 2 = 4.9, and being greater than one, indicated overdominance; and H^AHx = 0.19, a very low .' value associated with a highly asymmetrical d i s t r i b u t i o n of the dom-inant and recessive a l l e l e s i n the parents. (4DHj)r+F/(4DH 1) 2-F = 0.38, and being less than one, indicated a greater number of reces-sive than dominant genes were involved. T h e • h e r i t a b i l i t y f o r t h i s stage was very low, only 0.02, and at least 6 genes exhibited some degree of dominance. F r u i t Weight and Diameter i n Both Temperature Regimes In the warm regime, the values i n Table 19 show that D>Hi , which indicated p a r t i a l dominance; Hi>H 2, which indicated unequal numbers of dominant and recessive genes were involved; and F<0, which meant that r e l a t i v e frequencies of recessive a l l e l e s were high; ( (Hj/D) 2 = 0.48 and 0.25, and both being larger than zero but smaller than one indicated p a r t i a l dominance; H2/4Hj f o r both cchara'cteristics was very low, 0.20 and 0.15, and indicated asymmetrical d i s t r i b u t i o n of . dominant and recessive genes; and (4DHj)2+F/(4DH})2-F = 0.50 and 0.23, whichhwere smaller values than one, therefore there must have had more recessive than dominant genes af f e c t i n g each of the c h a r a c t e r i s t i c s . 80 H e r i t a b i l i t y f o r f r u i t weight was 0.44 and f o r f r u i t diameter was 0.48, and at least one gene and nine genes were exhi b i t i n g some degree of dominance aff e c t i n g f r u i t weight and diameter respectively. In the cool regime, the values i n Table.19 show that D>HX, which suggested p a r t i a l dominance; H1>H2, thus unequal numbers of posit i v e and negative a l l e l e s were involved; and F>0, which indicated more that the parents carried dominant than recessive genes which m f l u -3^  enced the ch a r a c t e r i s t i c s . The estimators (H 1/D) 2 =0.67 and 0.52 • f o r f r u i t weight and diameter respectively, and both values were be-tween zero and one which indicated p a r t i a l dominance; and E2/^i f o r both characters was 0.22, a very low value which indicated asym-metrical d i s t r i b u t i o n of the dominant and recessive a l l e l e s i n the parents. (4DH1)ls+F/(4DH1)i5-F = 1.83 and 1.82, and both values being larger than one, indicated more dominant genes than recessive genes influenced f r u i t weight and diameter. The h e r i t a b i l i t y values f o r these two characteristics were 0.91 and 0.97, and h 2/H 2 values i n -dicated at least 3 and 2 genes weee exhibiting some degree of domin-ance i n f r u i t weight and diameter respectively. B. Griffing'iS Method The res u l t s from the application of Gr i f f i n g ' s method showed a large number of s i g n i f i c a n t effects f o r general combining a b i l i t y (G.C.A.) and s p e c i f i c combining a b i l i t y (S.C.A.) which emphasize hereditary differences i n the i n d i v i d u a l stages of dif f e r e n t geno-types or c u l t i v a r s . G.C.A. and S.C.A. f o r each of the •Kegrowth component stages i n the warm regime were a l l s i g n i f i c a n t (Table 20). Also the differences between re c i p r o c a l crosses were only s i g n i f i c a n t 81 TABLE 20. Mean squares for general (G.C.A.) and specific (S.C.A.) combining a b i l i t y for the growth component stages i n warm and cool regimes. G.C.A. ' S.C.A. Reciprocal Effects Temperature Stage warm cool warm cool warm cool 1 3.3* 3.6* 3.1* 8.9* 0.2 1.6 2 1.8* 88.3* 2.7* 38.7* 5.9* 68.4* 3 230.5* 419.2* 56.3* 56.1* 2.5 4.3 4 17.9* 293.0* 26.1* 172.1* 7.0 34.7* 5 7.8* 13.4* 3.2* 18.9* 0.6 1.7* 6 242.6* 489.0* 7.4* 453.5* 8.0* 4.6 7 3.6* 0.4 1.0* 11.8* 0.1 0.9* * significant at 5% level TABLE 21:> Mean squares for general (G.C.A.) and specific (S.C.A.) combining a b i l i t y for the Stages 5 and 6 after hand-pollination treatment i n warm and cool regimes. G.C.A. S.C.A. Reciprocal Effects Stage Temperature  warm cool warm cool warm . cool 5 4.7* 11.8* 1.9* 2.0 1.1* 1.4 6 217.5* 188.4* 2.1 61.8* 10.1 9.7 * significant at 5% level 82 in.Stages 2 and 6. In the cool regime, both G.C.A. and S.C.A. i n a l l stages showed s i g n i f i c a n t effects except f o r Stage 7 (Table 20), and f o r the reciprocal crosses, Stages 2, 4-, 5 and 7 showed s i g n i f -icant differences. Regarcling days required f o r Stages 5 and 6 a f t e r the hand p o l l i n a t i o n treatment (Tablet) 21), there were s i g n i f i c a n t effects f o r the G.C.A. In both regimes; however the S.C.A. was less variable and only Stage 5, warm, and Stage 6, cool, showed s i g n i f i c a n t e f f e c t s . The recip r o c a l effects were not s i g n i f i c a n t except f o r Stage 5, warm. Considering days required per plastochron, the G.-C.A., S.C.A. and re c i p r o c a l effects were s i g n i f i c a n t (Table 22) i n the warm re-gime, whereas i n the cool regime, only the S.C.A. and re c i p r o c a l effects were s i g n i f i c a n t . Considering f r u i t weight and diameter, the G.C.A. showed s i g n i f i c a n t effects under both temperature regimes (Table 23), how-ever the S.C.A. showed s i g n i f i c a n t effects on the two characteristics i n the cool regime only. No differences were s i g n i f i c a n t between the reciprocals f o r f r u i t weight and diameter i n either temperature regime. C. Net Photosynthesis Rate i n Warm and Cool Regime Growth Chambers Space l i m i t a t i o n precluded r e p l i c a t i o n , thus the data i n t h i s experiment were not analyzed s t a t i s t i c a l l y . Inspection of the data from the warm regime (Table 24) shows that the net photosynthesis rate fluctuated with the di f f e r e n t plastochrons, and had a peak and a•• lowest point every 2 to 4 plastochrons. For example, B had an increased photosynthesis rate s t a r t i n g from the 4th plastochron to 83 TABLE 22. Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) combining a b i l i t y effects f o r days required per plasto-chron i n warm and cool regimes. Temperature Source of > • : — variance warm cool G.C.A. • 0.3* 0.2 S.C.A. 0.3* 0.4* Reciprocal Effects 0.1* 0.4* * s i g n i f i c a n t at 5% l e v e l TABLE 23: Mean squares f o r general (G.C.A.) and s p e c i f i c (S.C.A.) combining a b i l i t y effects f o r f r u i t weight and diameter i n warm and cool regimes. Temperature Source of Variance G.C.A. S.C.A. Reciprocal Effects 11756.8* 686.8 254.4 warm cool T r a i t f r u i t f r u i t f r u i t f r u i t weight diameter , weight. diameter 1058.15' 26.5 8.5 31336.1* 6508.2* 109.8 1329.4* 154.5* 9.9 si g n i f i c a n t at 5% l e v e l 84 to the 6th and then dropped down at the 7th and then rose again1. The I c u l t i v a r , had the lowest point at the 6th plastochron and then increased i t s rate. These fluctuations may be related to f l o r a l d i f f e r e n t i a t i o n . The hybrids BI and IB showed heterosis i n some stages and the fluctuation patterns were very close to those of I. The net photosynthesis rate f o r c u l t i v a r C was somewhat d i f f e r e n t from those of I and B, and had a peak every other plastochron, which again may be related to f l o r a l d i f f e r e n t i a t i o n , because i n accord-ance with the growth pattern of c u l t i v a r C, the flower clusters ap-peared very c l o s e l y , one a f t e r another, and there was only one l e a f between each of the f i r s t 3 to 4 clusters. The l e a f area data from t h i s d i a l l e l cross experiment •', (Table 24) show some trends. Taking the 8th plastochron f o r an ex-ample, c u l t i v a r B had the largest l e a f area and I had the smallest, and a l l the hybrids were intermed'iatee' between- t h e i r parents except i n the case of CB. There was an increase i n l e a f area f o r a l l the line s associated with the increase i n plastochron number. In most cases, there was a slow increase followed by a marked increase i n leaf area. In the cool regime growth chamber, the net photosynthesis rate (Table 25) f o r a l l the l i n e s was lower than i n the warm regime The hybrids showed heterosis i n some plastochron ages and the f l u c -tuation of the net photosynthesis rate varied with the hybrid l i n e . The l e a f area, as i n the case of the 8th plastochron f o r example, was greatest f o r c u l t i v a r B and the smallest f o r I. A l l the hybrids were imtermediate i n l e a f area between t h e i r parents, with the '. 85 TABLE 24.' Net photosynthesis rate and l e a f area i n growth chamber Experiment I i n warm regime. Plastochron Lines T r a i t 4 5 6 7 8 B ps. rate* 10.5 12.2 . 12.8 9.8 10.9 le a f areaf 72 109 148 202 322 ps. ratet- 11.1 10.0 5.5 11,1 12.0 I l e a f areaf 44 76 147 159 242 B l ps. rate 12.9 9.5 7.5 7.8 8.1 le a f area 47 88 135 233 300 IB ps. rate 13.6 13.0 9.8 10.3 9.4 l e a f area 47 111 158 220 279 ps. rate 9.3 10.0 8.0 9.4 8.4 C le a f area 51 93 168 254 301 BC ps. rate 8.2" 9.0 9.6 11.7 9.0 le a f area 46 78 109 202 305 CB ps. rate 9.6 10.3 9.7 9.1 8.0 leaf area 41 84' 112 189 265 IC ps. rate 7.1 6.3 6.0 8.4 8.-9 l e a f area 57 82 147 175 258 CI ps. rate 8.3 8.7 5ft 7 9.5 ' 7.5 leaf area 42 96 140 186 260 t ps. rate - net photosynthesis rate - mg C02/hr/dm2 Y l e a f area - cm2 86 TABLE 25; Net photosynthesis rate and l e a f area i n growth chamber Experiment I i n cool regime. Plastochron Lines T r a i t 4 5 6 7 8 B ps. ratet 6.9 6.9 7.4 4.2 5.1 leaf areaV 48 96 165 298 441 ps. rate 5.9 6.8 3.7 3.2 3.9 I l e a f area 48 70 134 179 257 BI ps. rate 6.7 8.6 4.9 4.2 4.4 l e a f area 66 102 183 217 414 IB ps. rate 6.7 7.1 4.7 4.6 . 4.1 l e a f area 65 100 170 247 325 ps. rate 6.4 7.3 4.2 5.3 .4.8 C le a f area 49 102 150 ' 237 332 BC ps. rate 7.5 6.7 6.3 5.0 4.6 le a f area 68 123 165 207 318 CB ps. rate 7.5 6.2 5.1 5.4 4.8 le a f area 66 81 161 282 382 IC ps. rate 3.5 4.3 4.6 3.3 3.1 l e a f area.. . . 72 124 184 279 . 357 CI ps. rate 4.9 4.4 3.8 3.8 5.5 le a f area 64 107 142 238 296 t ps. rate - net photosynthesis rate - mg C02/hr/dm2 ¥ l e a f area - cm2 87 exception of BC which was smaller and IC which was larger than both parents. Also at the 8th plastochron the l e a f areas between r e c i p -rocals showed very large differences. Reciprocal Cross'.^ Experiments 1. Growth Component Stages A. Warm Regime The data f o r the recipr o c a l cross experiment (Table 26, and -V^ppendix Tab'les i& angte!S).y) showedttheffdllowingiimportant d i f f e r -ences under the warm regime. The inter-parental comparisons between B and I showed s i g n i f i c a n t differences f o r a l l component stages ex-cept f o r Stage 5. The means show that f o r the 2 parental c u l t i v a r s , there were large differences because I was consistently e a r l i e r than B even f o r Stage 5 where the difference was not s i g n i f i c a n t . The in t r a - r e c i p r o c a l comparisons between the reciprocals BI._and. IB, which had the same nuclear composition, but a difference i n cytoplasm, showed no s i g n i f i c a n t difference i n earliness f o r any of the 7 stages (Table 26). In other words, the cytoplasms-P^ (from c u l t i v a r B) and P 2 (from c u l t i v a r I) had the same effects on the days required per stage. Differences between the maternal parents and t h e i r offspring could be attributed t o differences i n nuclear gene composition be-cause both generations have the same cytoplasniic composition. In the case of I vs. IB, only Stage 3 showed a s i g n i f i c a n t difference and f o r B vs. B I S t a g e s 1, 2, 3, 4 and 7 showed s i g n i f i c a n t d i f f e r -ences f o r earliness. In other words, the differences between • 88 TABLE 26. The non-orthognal comparisons f o r the seven growth component stages i n the re c i p r o c a l cross Experiment I under warm and cool regimes. Sums of squares Stage Line;. - Mean B .vs I B l vs IB I vs IB B vs B l • B 8.1 (20.1)1 1 1 7.2 (17.0) 4.1* 0.1 0.1 4.1* B l 7.2 (17.1) (48.1*) (5.0*) (6.1*) (45.0*) IB 7.2 (17.8) B 7.9 ( .9.7) 2 1 6.4 ( 9.2) 11.3* 0.5 1.8 7.2* B l 6.7 ( 8.6) (1.3) (1.8) (7.2*) (6.1*) IB 7.0 ( 8.0) • B 32.1 (31.2) 3 1 19.0 (19.3) 858.1* 14.5 245.0* 304.2* B l 24.3 (25.4) (708.1*) (48.1*) (423.2*) (168.2*) IB 26.0 (28.5) B 32.8 (65.0) 4 1 24.3 (49.8) 361.3* 5.0 0.8 312.1* B l 24.9 (50.7) (1155.2*) (217.8*) (281.3*) (1022.5*). IB 23.9 (57.3) B 7.2 ( 9.5) 5 1 6.4 (10.2) 3'i2 2.5 0.1 0.2 B l 7.0 ( 9.1) (2.5) (0.2) (9.8) (0.8) IB 6.3 ( 8.8) B 35.6 (59.7) 6 1 32.4 (51.7) 135.2* 28.8 0.2 45.0 B l 32.6 (41.3) (320.0*) (16.2) (369.8*) (1692.8*) IB. . . .30.2 (43.1) B 9.4 ( 9.8) 7 • 1 5.6 ( 9.5) 72.2* 0.2 0.5 76.1* B l 5.5 ( 9.4) (0.2) (4.1) (7.2) (0.1) IB . .5.3 ( 8.5) * s i g n i f i c a n t at 5% l e v e l t Means and sums of squares i n brackets are from data from the cool regime to contrast with the unbracketed values from the warm regime. 89 nuclear compositions XY and YY were not as great as the differences between XY and XX. B. Cool Regime The data f o r the re c i p r o c a l cross experiment (Table 26) showed the following important differences under the cool regime, . and some contrasts with the resu l t s of the same l i n e s grown i n the warm regime. The inter-parental comparisons between B and I were s i g n i f i c a n t l y different f o r Stages 1, 3, 4 and 6 only. Cult i v a r B required more days to complete each stage except f o r Stage 5, i n which the re s u l t s are the reverse of the observations f o r the warm regime. Stage 7 showed no s i g n i f i c a n t difference between B and I although I was e a r l i e r than B, following the same trend as i n the warm regime. For the T1 i n t r a - r e c i p r o c a l comparison between BI and IB, s i g n i f i c a n t differences i n earliness for Stages 1, 3 and 4 were observed, and such differences were not observed i n the warm regime. In the case of maternal parents and offspring ( I vs. IB and B vs. BI) differences were s i g n i f i c a n t f o r Stages 1, 2, 3, 4 and 6. 2.- Net Photosynthesis Rate A. Warm Regime The differences i n net pptotosynthesis rate between the parents B and I (Table 27 and Appendix Tables 16 and 18) were not si g n i f i c a n t u n t i l plastochrons 6, 7 and 8 developed. The differences between the rec i p r o c a l hybrids were not s i g n i f i c a n t u n t i l plastochron 5 and l a t e r , 8 were developed. Considering the maternal parents vs. offspring comparisons, I vs. IB, showed differences which were a l l 90 TABLE 27. The non-orthoghal comparisons for the net photosynthesis rate in the reciprocal cross Experiment I I under warm and cool regimes, (mg C02/dm2/hr). Sums of squares P.A. 1 Line Mean B vs I BI vs-IB I vs IB B vs BI B 10.6 ( 9.9)f 4 I 12.7 ( 9.0) 8.8 1.3 39.4* 65.7* BI 16.4 (10.3) (1.4) (1.3) (8.6*) (0.4) IB 17.2 (11.1) B 15.9 ( 8.7) 5 • I 14.7 (9.2) 3.0 12.6* 6.7 7.2 BI 14.0 ( 9.7) (0.4) (28.5*) (36.9*) (1.9) IB 16.5 (13.5) B 10.9 ( 5.7) 6 I 6.1 (11.9) • 45.7* 6.2 51.7* 4.3 BI 9.4 (10.9) (76.9*) (0.4) (0.6) (53.8*) IB . . 11.2 (11.3) B- 10.6 (10.5) 7 I 20.5 ( 5.4) 193.7* 20.6 191.7* 19.9 BI 7.5 ( 8.2) (51.8*) (0.8) (9.5) (10.3) IB 10.7 ( 7.5) B 8.3 ( 5.4) 8 I 9.4 ( 7.9) 2.6* 8.2* 1.8* 6. 8* BI 6.5 ( 3.4) (12.4*) (4.4) (18.9*) (8.6*) IB 8.4 (A.8) t P.A. = plastochron age ¥ see Table 26 notation * significant at 5% level 91 s i g n i f i c a n t except i n plastochron 5; however, i n the case of B vs. B l , only plastochrons 4 and 8 showed s i g n i f i c a n t differences. The fluct u a t i o n patterns f o r the net photosynthesis rate i n the re c i p r o c a l Q hybrids are shown i n Fig. 25. Both hybrids showed heterosis i n plas-tochron 4 and then a decrease u n t i l the 8th plastochron, at which stage the hybrid IB was intermediate between the parents, but B l was lower than either parent. Cultivar I had i t s lowest point at plasto-chron 6 and a peak at plastochron 7 whereas the other l i n e s did not show such marked fluctuation. B. Cool Regime The differences i n net photosynthesis rate between B and I (Table 27) were s i g n i f i c a n t at plastochrons 6, 7 and 8 as was the case i n the warm regime, but the differences between the reciprocals were s i g n i f i c a n t only at plastochron 5.' The I vs. IB comparison showed s i g n i f i c a n t differences i n plastochrons 4, 5 and 8. In the case of B vs. B l only the 6th and 8th plastochrons showed s i g n i f i c a n t differences. In Fig. 26, i t can be seen that the re c i p r o c a l hybrids showed heterosis f o r net photosynthesis rate at plastochrons 4 and 5.' Then the rate was intermediate between parents i n plastochrons 6 and 7, and f i n a l l y lower than both parents at the 8th plastochron. Cult i v a r I had the lowest net photosynthesis rate at the 4th plastochron, at-tained a peak at the 6th, then decreased markedlylat the 7th and f i n -a l l y increased sharply again. Cult i v a r B had a peak at the 7th plas-tochron and then decreased. 3.' 92 93 3. Leaf Area A. Warm Regime The leaf area differences between parents B and I were s i g n i f i c a n t f o r plastochrons 5 to 8 (Table 28 and Appendix Tables 17 and 19). There were no s i g n i f i c a n t differences between the r e c i -procals i n any of the plastochrons. Comparing maternal parents and t h e i r o f f s p r i n g , I vs. IB, showed s i g n i f i c a n t differences f o r a l l plastochrons except i n the 4th, and i n the case of B vs. B l , only the 4th and 8th plastochrons showed s i g n i f i c a n t differences i n l e a f areas. In Fig. 27, at plastochron 4, c u l t i v a r B had the largest l e a f area, and the recipr o c a l hybrids had smaller l e a f areas than both parents. Leaf area i n a l l the l i n e s increased sharply from the 5th plastochron, except I which increased sharply at the 6th. Thy hybrid, B l , showed heterosis f o r l e a f area at the 7th and 8th plastochrons. B. Cool Regime The leaf area differences between parents B and I (Table 28) were s i g n i f i c a n t f o r a l l plastochrons. There were s i g n i f i c a n t differences between the rec i p r o c a l hybrids at the 7th and 8th plas-ochrons only. Comparing the differences i n leaf area between mat-ernal parents and t h e i r o f f s p r i n g , I vs. IB^ had s i g n i f i c a n t d i f f e r -ences at a l l plastochrons except at the 5th, but i n the case of B vs. B l , only the differences at the 5th and 8th plastochronswere s i g n i f i c a n t . In Fig. 28, i t i s obvious that both hybrids showed heterosis when t h e i r l e a f areas increased sharply at plastochrons 7 and 8. Cultiv a r I had the smaller l e a f areas from the 4th to the 8th plastochron. 95 TABLE 28;- The non-orthoghal comparisons for the leaf area i n the reciprocal cross Experiment I I under warm and cool regimes. (cm2). Sums of squares• P.A.T Line Mean B vs I BI vs IB I vs IB B vs BI B 62.2 ( 57.5)¥ "4 I 50.5 ( 36.8) 276.1 36.1 112.5 450 .1* 31,2' >.7.020.( 60.0) (861.1*) (128.0) (1081.1*) (60 .5) 'IB..Q ,"43?00<i 52.0) 5 B I 95.2 (114.3) 65.7 ( 88.5) 1770.1* 0.5 1512.5* 6 .1 BI 93.8 ( 98.5) (1526.1*) (98.0) (200.0) (1035.1*) IB 93.2 ( 91.5) B 154.0 (166.5) 6 I 97.0 (115.8) 6498.0* 112.5 5050.1* 406.1 BI 139.7 (156.0) (5151.1*) (1.1) (3240.1*) (253.1) IB 147.2 (155.3) 2'u2:5 '-0"RS £ 242:5 '(186.8) 7 i 164.5 (165.3) 12324.5* 288.0 11552.0* 180.5 BI 252.0 (224.3) (924.5*) (1431.1*) (6962.0*) (231.1) IB 240.0 (197.5) B 373.0 (213.8) 8 I 284.0 (191.3) 15931.1* 288.0 23220.0* 1810.5* BI 403.1 (274.0) (1012.5*) (2043.0*)(13695.0*) (1596.1*) IB 391.7 (242.0) f P.A. = plastochron age see Table 26 notation significant at 5% level 96 97 300 "~4 5 6 7 8 P L A S T O C H R O N F i g . 28. Leaf area of each plastochron among the l i n e s i n cool re^ffie?.tux\^ ? regime. 98 F i e l d Experiments I." Experiment I F i e l d Experiment I was handled i n two parts. Part 1 exam-ined 8 l i n e s which included parents, B and I; t h e i r r e c i p r o c a l hybrids IB and BI, and the backcrosses IBxI, BIxI, BIxB and IBxB. The days required f o r the Stages. A and C were recorded f o r a l l T.2 -slants i n each l i n e and the data are shown i n Table 23- of the Appendix. The comparison among the l i n e means (Table 29) showed large d i f f e r -ences i n the days • required f o r both stages f o r the .••..2 '• parents, I and B, and I was e a r l i e r than B. The differences between re c i p r o c a l hy-brids were very small and both of the hybrids were intermediate be-tween t h e i r parents. Both the rec i p r o c a l hybrids were e a r l i e r i f backcrossed to the early parent, I , than i f backcrossed to the l a t e parent B. One of the backcross progenies I?Bxi'Iwas very close to the early parent I f o r the t2ra stages, whereas another progeny BIxB was TABLE 29: Mean days required f o r Stages A and C i n the f i e l d Experiment I , part 1. Line Stage I B IB BI IBxI BIxI IBxB BIxB A 68.9 80.8 74.6 74.8 . 69.5 70.6 76.8 79.5 B 47.3 59.7 ' 52.3 51.0 48.4 50.5 53.3 55.5 closer to the la t e parent B i n Stages A and C. Part 2 examined t2/u, segregating generations of the r e c i p -rocals BI and IB, denoted BIF 2, IBF 2, BIF 3 and IBF 3. The means f o r 99 the earliness i n Stages A and C f o r each of the 4 progenies were based on 100 plants i n each progeny. The mean number of days required f o r BIF2 and IBF2 i n both stages (Table 30) were very s i m i l a r , but these reciprocals showed larger differences i n the F3 generation, and were e a r l i e r than the F 2 generation. The standard deviations f o r the F3 were larger than those f o r the F 2, which indicated that segregation was continuing. Since there were larger ranges f o r the F3 than f o r the F 2 i n both stages, then the selection f o r earliness would be more.ef-fe c t i v e i n the E.3. The plants which were e a r l i e r than the parents f o r Stages A and/or C were subjected to pedigree s e l e c t i o n , t h a t - i s seed from each i n d i v i d u a l plant selection was kept separate f o r the next generation. In the IBF3, population, 6 early plants were s e l -ected, and s i m i l a r l y i n the BIF3, 11 early plants were selected. TABLE 30: The mean number of days required f o r Stages A and C i n the f i e l d Experiment I , part 2. Line Stage A Stage C Bl F 2 75.1+4.0 49.9±4.8 IB F 2 75.6±4.8 49.1+4.6 B l F 3 72.1+8.7 49.2±5.5 IB F 3 70.7±7.7 51.1+5.1 j i ' i ' i Experiment I I The progenies from the i7vmiividHa^p^anis. selected " from the F| rec i p r o c a l populations i n Experiment I , part 2 (1971), were grown i n the f i e l d (1972) i n plots with 25 plants per progeny. 100 •The mean f o r the IB F 4 Stage A was 66.6 ±5.7 days and f o r Stage C was 49.5 ± 3.4 days (Table 31). The B l F^ Stage A was 66.8 ± 6.8 days and Stage C 47.3 ± 4.7 days. These means were a l l intermediate between those of the o r i g i n a l parents B and I , but had the tendency-to be closer to the early parent I. Approximately 10% of the e a r l -i e s t segregates of the IB F^ and B l F^ were pedigree selected f o r earliness and used to provide the F5 progenies. TABLE 31: Means, h e r i t a b i l i t y , selectioneprogress and genetic pro-ggress auidJgegeheratibns. IB Th B l F i t Stage A Stage C Stage A Stage C Mean 66.6±5.7 49. 5±3.4 66.8±6.8 •47.3±4.7 0.63 0 .57 0.81 0.66 op (days) 5.70 3 .40 6.80 4.70 i 1.75 1 .75 1.75 1.75 AG (days) 6.30 3 .40 9.60 5.40 oG (days) 4.60 2 .60 6.20 3.80 The h e r i t a b i l i t i e s f o r both Stages A and C i n the re c i p -r o c a l cross populations were r e l a t i v e l y high, but Stage A had higher h e r i t a b i l i t i e s than Stage C (.Table 31). The calculated or expected selection progress, AG, ^following the models of Falconer (1967) and Pirchner (1969), as shown on -pagewas 6.30 days i n Stage A and 3.40 days i n Stage C f o r IB F^ selections, and 9.60 days and 5.40 days f o r B l F4 selections i n Stages A and C respectively. The genetic 101 progress, qG, was 4.60 days and 2.60 days f o r Stages A and C res-pectively i n the IB F ; but was 6.20 and 3.80 days f o r Stages A and C i n the BI F . /..3 - ' Experiment I I I Part 1. Seed from the e a r l i e s t 10% of the IB Fk and BI F 4 which were pedigree selected i n 197.2 was used i n t h i s Part of the exper-iment. The means (Table 32) for Stages A and C i n the IB F 5 were 60.3 and 50.5 days respectively, and s i m i l a r l y 61.0 and 49.2 days for the same stages of the BI F 5 i n 1973. A l l these means were ear-l i e r than both of the parents, B and I , ind i c a t i n g that selection for the shortest length recombinations was being r e a l i z e d . Part 2. Six l i n e s from the F 4 generation selected f o r e a r l -iness ( i n 1972) were compared t o ±Wo l i n e s selected f o r lateness from the F 4 generation.^ (Tables 32). The means of the £6bt selected early l i n e s f o r both stages A and C were a l l e a r l i e r than both parents, ex-cept one l i n e (11-22-13) showed one day l a t e r than the e a r l i e r parent I i n Stage A. The f2/6 l a t e s t l i n e s i n both stages were a l l i n t e r -mediate between t h e i r o r i g i n a l parents B and I , but showed the tend-ency of being closer to the l a t e r parent B. A l l the means of these selected F5 pedigree genes f o r earliness were no e a r l i e r than t h e i r F4 parents, although some of the plants within each l i n e were close to the parent value. These differences are^confounded with season, but the data may indicate a minimal number of days are required to grow through a certain stage, and selection may not able to go bey-ond t h i s threshold. 102 TABLE 32: Mean days required for selections, ira.de for Stages A and C in the F5 of the f i e l d Experiment I I I . " Part 1. Mass Populations Stage Parental line Mean (days) B 74.0+.2.0 A I 62.0+2.2 Bl F 5 61.0+3.5 IB Fs 60.313.3 B 61.0+.4.4 C I 52.6±3.7 Bl F 5 49.213.7 -IB F§ 50.51.4.4 Part 2 . Pedigree Populations Stage Parental line Line No.t Mean (days) B 7 4 . 0 1 2 . 0 I 6 2 . 0 1 2 . 2 IB F 5 1-48-18 5 9 . 6 1 3 . 3 Bl F 5 1 1 - 5 3 - 2 0 6 0 . 6 1 3 . 2 A Bl F 5 11-53-19 60.811.9 Bl F 5 1 1 - 5 3 - 2 2 6 1 . 8 1 3 . 2 B K F 5 I I - 2 2 - 1 58.312.8 Bl F 5 11-22-13 63.214.0 IB F 5 1-26-16 7 1 . 2 1 1 . 9 B I F 5 11-50-23 7 3.811 . 9 B 61.014.4 I 5 2 . 6 1 3 . 7 IB F 5 1-48-18 5 0 . 6 1 3 . 4 B I T 5 1 1 - 5 3 - 2 0 4 8 . 6 1 4 . 6 n Bl F 5 11-53-19 46.812.9 Bl F 5 1 1 - 5 3 - 2 2 48.213.8 Bl F 5 TI - 2 2-1 52.013.6 Bl F 5 11-22-13 4 9 . 6 1 5 . 5 IB F 5 1-26-16 58 . 8 1 3.1 Bl F 5 11-50-23 5 8 . 6 1 3 . 4 TLine No. 1-48-18, 11-53-20, 11-53-19, 11-53-22, selected from F 4 the earliest lines for Stage A. Line No. II-22-1, 11-22-13 selected from F^ the earliest lines for Stage C. Line No. 1-26-16, 11-50-23 selected from F^ the latest lines for Stages A and C. 103 4.. Results of selection i n the f i e l d experiments Stage A. As shown i n Table 33, the random samples were taken from the Tl and F 2, and selection f o r earliness i n Stage A was begun i n the F 3 i n which 6% and 11% were chosen i n the IB F 3 and BI F 3 res-pectively. The IB F 4 mean f o r earliness was 66.6 days, which was 6 days e a r l i e r than B, but 3 days l a t e r than I ; whereas the BI F^ mean was 66.8 days, which was 5.9 days e a r l i e r than B, and 3.5 days l a t e r than I. The e a r l i e s t of the 10% of the plants were selected i n these reciprocals, and the recipr o c a l F5 populations were e a r l i e r than both o r i g i n a l parents. The IB F 5 was 13.7 days e a r l i e r than B and 1.7 days e a r l i e r than I , and BI F 5 showed 12.9 days e a r l i e r than B, and 1 day e a r l i e r than I. Stage C. Similar selection procedures were used as f o r Stage A, and the IB F^ means (Table 34) were 6.5 days e a r l i e r than B and :;3..1 days l a t e r than I ; whereas the BI F^ showed 8.7 days e a r l i e r than B''and 0.9 days l a t e r than I. After the e a r l i e s t 10% of the F^ plants were selected, the means f o r the F 5 progenies were e a r l i e r than both parents. The IB F 5 was 10.6 days e a r l i e r than B and 2.1 days e a r l i e r than I , ' v whereas the BI F 5 was 12.1 days e a r l i e r than B and 3.6 days e a r l i e r than I. The means f o r earliness of the F 5 generation progenies of both recip r o c a l populations were smaller than the e a r l i e s t o r i g i n a l parent, in d i c a t i n g that there was recombination f o r earliness between the two stages. In other words, the shortest stages had been brought together i n the F 5 r e c i p r o c a l hybrid populations tojprdduce.the- early segregants." 104 TABLE 33: Summary of the f i e l d experiments, mean days required for Stage A. IB T1 4-IB F 2 4 IB F 3 IB F 4 IB F 5 74.612.3 random sample taken 75.614.8 Handom sample taken 70.7+.7.7 different from B-9.1; I +117 (6% selected) 66.615.7 different from B -6.1; I +33CJG (10% selected) 60.3±1.6 different from B -13.7: I -1.7 BI Fj 4 BI F 2 4 BI F 3 BI Fh BI F 5 74.8H.5 random sample taken 75.H4.0 random sample taken 72.H4.0 different from B -8.7; I +3.1 (11% selected) 66.8±6.8 different from B -5.9; I +3.5 (10% selected). .61.0+4.6 different from B =12.9: I -1.0 TABLE 34: Summary of the f i e l d experiments, mean days required for Stage C. IB Fi 4 IB F 2 4 IB F 3 IB F 4 m IB F 5 52.312.3 random sample taken 49.1±4.6 random sample taken 5111*511 different from B -8.6; I +3.7 (6% selected) 49.5±3.4 different from B -6.5; I +3.1 (10% selected) 50.5+2.3 different from B -10.6: I -2.1 BI Fi 51.011.0 random sarandomasample taken BI F 2 BI F 3 BI Fh + BI F 5 49.9±4.8 randomssampiettiaken 49.213.5 different from B -10.5; I =1.9 (11% selected) 47.314.7 different from B -8.7; I -0.9 (10% selected) 49.016.7 different from B -12.1; I -3.6 105 DISCUSSION D i a l l e l Cross Experiments In the breeding of s e l f - p o l l i n a t e d crop plants, the e f f i c -iency depends on accurate i d e n t i f i c a t i o n of the hybrid combinations that have the po t e n t i a l of producing maximum improvement. The present experiments were undertaken to determine whether d i a l l e l analysis of parental and F -^data could provide information useful f o r producing a maximum earliness. The data from the d i a l l e l cross experiments were subjected to 2 a n a l y t i c a l procedures. In the "Hayman and Jinks method" a l l the assumptions are tested i n i t i a l l y by the uniformity of Wr-Vr among arrays. Hayman (1957, 1958) reported that only when the t e s t reveals a lack of uniformity i s there need f o r further tests t o investigate which assumption i s not v a l i d . One of the common ways i s to eliminate certain parental l i n e data and analyze the remaining data again. Due to l i m i t e d resources f o r t h i s experiment, there were only 3 parental l i n e s involved; therefore, when data f o r certain c h a r a c t e r i s t i c s i n the present experiments f a i l e d t o pass the uniformity t e s t , i t was not possible to e]jjirinate a parental l i n e and apply a further t e s t . As shown i n Table 5, there were 3 out Of 24- characteristics which 1: f a i l e d the uniformity t e s t . Nevertheless these 3 p a r t i a l f a i l u r e s seemed u n l i k e l y to introduce gross bias i n t o the t o t a l genetic i n -formation to be gained from the d i a l l e l experiments; therefore, i t was assumed that these p a r t i a l f a i l u r e s would not detract from the t o t a l information gained. 106 According to Hayman ( 1 9 5 4 ) , the interaction between environment and:the genotype-in a d i a l l e l cross'is.revealed by the amount of heter-ogeneity of the variances within parental and Fi families. Such heter-ogeneity may be handled by considering the environmental effects (E) which i s estimated from differences between blocks, and subtracted from the genetic parameters, as shown i n Table 1. Peat (1964) repor-ted that i t i s d i f f i c u l t to separate the environmental effect from the genetic effect on certain characteristics, and that using the phenotypic variance w i l l result i n a bias. In greenhouse Experiments I and I I , there were two negative D values; Stage 2, warm (Table 13) and days required per plastochron, warm (Table 18). These negative values are a result of sample error and also the subtraction of the relatively large environmental effect E from the parental variance, V , (i.e. D=V -E; as shown i n Table 1). Since both these character-P P i s t i c s , Stage 2 (from seed germination to f i r s t true l e a f ) , and the days required per plastochron (the mean of 3rd to 8th plastochron) both occurred before transplanting to the benches when the distance between seedlings was only 2 inches, then, there was the possibility of competition between the seedlings which may have caused the E value to be so large. . Hayman and Jinks d i a l l e l cross theory proposed the use of the parameters F, Hj and H 2, expecting them to be accurate i n a large d i a l l e l cross experiment. Hayman (1956) suggested that when the num-ber of parents i s less than 10 none of the components of variation i n the d i a l l e l cross analyses would be significant estimates of pop-ulation parameters. However, i n this experiment, the individual par-ents and crosses were the main interest, and no attempt was made to 107 measure the population parameters, thus the genetic information was limited to parental cultivars I, B and C only. The analysis of a d i a l l e l cross experiment i s somewhat different from the usual anal-ysis of variance because the former- estimates the components sepa-rately from within each replicate, but the latter from over a l l replicates. The value of the numerical method of analysis i s that the relative importance of dominance and additive effects and some infor-mation on the distribution of a l l e l e s within the parental population can be obtained i n numerical form, and from these, further estimates such as the degree of dominance can be obtained. In these experiments, the numerical analysis indicated that i n the warm regime, overdominance occurred i n Stages 1, 2 and 4, pa r t i a l dominance i n Stages 3, 6 and 7, and only Stage 5 showed virtual l y complete dominance. Previous studies by other workers on earliness did not partition the l i f e cycle into as many component stages as the present work. In general the inten-sive partitioning results do agree with some of thecearlier reports on larger component stages. The present Fx's were usually;?earlier than the earliestjparent i n both flowering and f r u i t set, s i m i l a r t o -the reports by Hayes and Jones (1917). Wellington (1922), and Powers and Lyon (1941). The earliness, expressed as days to f i r s t flower appears to be a result of overdominance i n Stages 1, 2 and 4, and ; these are a large part of the stage described by Burdick (1954) and Young (1966) who reported that time of flowering i n hybrids i s approx-imately intermediate between the two parents and their results would exclude overdominance action. Either their parental types behave differently, or the failure to partition growth eomponent stages 108 sufficiently prevented them from observing the overdominance as found in Stages 1, 2 and 4 of the present experiments. These stages ac-count for about one half of the time period between germination to flowering, thus the importance of this period for earliness i s self-evident. In this experiment Stage 5 showed almost complete dominant gene action wMeh?vwas i n agreement with Corbeil (1965) and Corbeil and Butler (1965), who reported that the early maturity genes were completely dominant for the f i r s t bloom to f i r s t f r u i t set stage which i s the ; same as Stage 5 i n the present study. In.the cool regime, results were quite different. Over-dominance for earliness was shown i n Stages 1, 5, 6 and 7; par t i a l dominance i n Stages 2 and 3, and complete dominance i n Stage 4. Com-paring the results under the 2 different temperature regimes, the genetic parameters were the same i n only Stages Land 3 i n which there was overdominance and pa r t i a l dominance respectively, and a l l other component stages had different gene";action. These differences are thus indicated to be due to the genotypeeenvironment interaction. In the warm regime, the frequency of recessive genes for earliness was higher than dominant genes for Stages laand 2, and the opposite way for Stages 3, 4, 5, 6 and 7. The gene number involved i n the. seven component stages was relatively low, i n the warm regime only one or 2 gene pairs exhibited some degree of dominance for Stages 1} 2, 3-and 2 gene pairs for Stages 2, 3 and 4 respectively5 and 4 gene pairs for Stages 5, 6 and 7. These results were somewhat d i f -ferent from those of Honma>'e£-.al. (1963), who reported only one major gene pair for days required from seeding to f i r s t flower. In contrast, 109 Powers et a l . (1950) and Fogel and Currence (1950) suggested 3 or more gene pairs controlled t h i s character of earliness of flowering, and the former also reported that 2 major genes appeared to control the stage f o r f r u i t s e t t o f r u i t ripening. In the cool regime, a larger number of genes appeared to be involved i n the earliness of most stages. Comparing the r e s u l t s i n Tables 14 and 16, i t i s seen that i n the cool regime, a larger number of genes were involved i n each of Stages 1 to 4 i n c l u s i v e than i n the warm regime which represented usual growing conditions f o r the commercial crop and previous research work. At the l a t e r stages, Stage 5 had the same h 2/H 2 value under both regimes, and Stages 6 and 7 had lower values under the cool regime ind i c a t i n g probably one gene pai r only showed some measure of dominance. These differences i n gene numbers exhibiting some degree of dominance de-pending on the temperature l e v e l are evidence that plant breeders should r e a l i z e that such responses can be studied i n t h e i r breeding programmes. I d e n t i f i c a t i o n of genotypes of spe c i a l value f o r cool climates or growing seasons i s a "problem f o r the plant breeders "screening procedures" i n i d e n t i f y i n g useful genotypes f o r providing wider adaptation to less favourable temperature conditions. The h e r i t a b i l i t i e s f o r Stages 3 and 6 in^the warm regime are high suggesting that s e l e c t i o n " i n the early generations such as the F 2 could be expected to show progress i n increased earliness. These two stages are very long components of the l i f e c y cle, there-fore, they should provide a good opportunity to make progress with earliness. The other stages i n the warm regime, and a l l stages i n the cool regime, had lower h e r i t a b i l i t i e s , thus early generation 110 selection could not be expected to make much progress i n the d i r e c t i o n of increased earliness. Greenhouse Experiment I I This experiment contrasted Stages 5 and 6 of the previous greenhouse Experiment I where.natural s e l f - p o l l i n a t i o n occurred, with results of greenhouse Experiment I I where pollen was transferred by hand. Although the data f o r the two experiments, show small differences f o r Stages 5 and 6, these differences were undoubtedly a r e s u l t of v a r i a -t i o n i n the two seasons, and both experiments showed the same responses when genetic parameters and estimators were calculated. In other words, the differences i n earliness as affected by natural or a r t i f i c i a l p o l -l i n a t i o n were not large enough to aff e c t the genetic information on earliness. Apparently spe c i a l p o l l i n a t i o n handling was not needed, and growth studies can depend on natural p o l l i n a t i o n t o produce a uniform base f o r plants i n t h e i r Stage 5. As expected, days required per plas-tochron, which were recorded from 4-th to 8th plastochron, '.'were markedly affected by the temperature regimes. The relationship of the D and E1 parameters > (Table 18) indicated complete dominance f o r earliness i n the warm temperature regime, but overdcminance i n the cool temperature regime. The gene number involved i n t h i s earliness d i f f e r e d with temp-erature, being 2 and 6 i n the warm and cool regimes respectively, and the h e r i t a b i l i t i e s were both very low. Nevertheless i t could be impor-tant to know the temperature-genotype interactions to aid the plant breeder i n choosing breeding procedures; f o r example,. the true-breeding c u l t i v a r s could be selected f o r the daninant action f o r ea r l i n e s s , under warm conditions; however under the stress of cool regimes the use of 111 F]_ hybrid c u l t i v a r s could be the desirable choice, p a r t i c u l a r l y to get the overdominance' • f o r earliness. In contrast to the character of e a r l i n e s s , the genetic parameters f o r the f r u i t weight and diameter show the same response i n both temperature regimes. The smaller size and diameter of f r u i t of Fj hybrids compared with the parents (Table 11) were apparently the r e s u l t of p a r t i a l dominant gene action (Table 19 and Fig. 21 to 24-), and such r e s u l t s are i n agreement with the reports of Fogle and Currence (1950) and K h e i r a l l a and Whittington (1962) on tomato; f r u i t size inheritance. The p i c t o r i a l analyses,, wraehhare genetic analyses using d i a l l e l cross graphs (Fig. 1-24), are bases on the value of W -V^. The value of W -V i s equal to^D-Hi) (Hayman, 1954), and must be constant among the arrays to meet the assumption of the d i a l l e l cross theory. I f the value of ^(D-Hi) does not change and remains constant, then Wr= constant +Vr, and the regression of W^  upon V i s a straight l i n e of unit slope. When V = 0, then W^  = ^(D-Hi). Thus on the d i a l l e l l o r o s s (W ,V ) graphs, the intercept on the W^  axis i s an i n -d i c a t o r y o f the average degree of dominance i n the progeny. With par-t i a l dominance, the W^  intercept i s p o s i t i v e ; with overdominance the W intercept i s negative. Therefore the (W ,V ) graph provides e v i -dence of the presence of dominance (b^O) and the average degree of dominance (+ or - value of a). In the present experiment the results, of p i c t o r i a l analyses reveal that the average degree of dominance i n a l l the characters investigated was i n agreement with the r e s u l t s of the numerical analyses. Besides t h i s point, the p i c t o r i a l analyses provide further information which i s not obtained from the numerical 112 procedure. For example, the position of the regression line related to the origin (W ,V ) gives a good idea of the degree of dominance; and the position of points along the line reveals the distribution of dominant and recessive alleles within the parental populations. Points near the origin (W ,V ) represent parents with mostly dominant a l l e l e s , whereas points near the upper end of the regression line represent parents with mostly recessive alleles. From Fig. 1 -7 , i t may be concluded that i n the warm temperature regime, the I cultivar carried dominant genes for earliness in a l l the 7^component stages, and B carried recessive genes which were acting i n the direction of lateness. On.the other hand, Fig.8-14 show that i n the cool temperature regime, I cultivar carried genes for earliness in only Stages 3 ,4 ,5 and 6 , whereas i n Stage 2 dominant earliness was shown by cultivar B; and the. dominant earliness for Stages 1 and 7 was manifested by cultivar Cv This variation from results i n the warm regime could be due to different genotype-environment interactions, and certain genes i n certain cultivars were more suitable for growth i n the cool temp-erature environment. I t has already been reported (Young, 1963) that C cultivar seed i s able to germinate at the cool temperature of 1 0 . 0 ° C and set f r u i t at 7 .5°C night temperature. From the plant breeder's point of view, the p i c t o r i a l analysis supplies information about the gene distribution pattern among parents and such information i s not obtained i n the numerical analyses. In this experiment, cultivar I i s desirable for the breeding of earliness,.because i t carries dominant genes i n most of the growth component stages, and these dominant genes are i n the direction of earliness. 113 Additional to the Hayman-Jinks procedure f o r d i a l l e l cross experiments, the G r i f f i n g ' s method was also used, and i t i s concerned with the general combining a b i l i t y (G.C.A.) and s p e c i f i c combining a b i l i t y (S.C.A.). According to Spragueand latum (194-2) the v a r i -ance f o r G.C.A. I s largely additive genetic variance, whereas S.C.A. i s largely dominance variance. Horner and Lana (1956) indicated that both G.C.A. and S.C.A. contain e p i s t a t i c variance with the l a t t e r containing considerably more than the former. From the res u l t s (Tables 20 and 21), i t indicated that i n the warm regime, the estimates of variances f o r G.C.A. were s i g n i f i -cant attthe 5% l e v e l f o r a l l 7 component growth stages, i n d i c a t i n g the presence of additive gene action. Although s i g n i f i c a n t estimates of S.C.A. were also obtained, when compared to G.C.A.,,- the estimates of non-additive genetic variance (S.C.A.) were generally smaller, especially i n Stages 3 and 6. In the cool regime, the estimates of G'i-C.A. f o r a l l the component stages were s i g n i f i c a n t except f o r Stage 7 whereas-the estimates of S.C.A. were a l l s i g n i f i c a n t . The mean squares of the S.C.A. were larger than those f o r G.C.A. i n Stages 1, 5 and 7 which indicated that non-additive. The s i g n i f i c a n t non-additive gene action should make fa xrecurrent selection more e f f i c i e n t in;.the early generations i f selection i s f o r earliness under a cool regime. The foregoing demonstrates the contrast i n gene action under d i f f e r i n g temperature regimes, and choice of breeding methods should obviously be related t o the objectives and use of growing conditions f o r plant breeding programmes. 114 Considering the days required per plastochron (Table 22) i n the warm regime, the G.C.A. and S.C.A. values were both s i g n i f i -cant whereas i n the cool regime, the S.C.A. value was larger than and hence more important than the G.C.A. This high S.C.A. value ' indicated that t h i s c h a r a c t e r i s t i c of earliness can be considered as r e l a t i v e l y e a s i l y t o select and evaluate i n a population under selection. This conclusion i s s i m i l a r t o that of Khalf-Allah (1970), Khalf-Allah and Peirce (1962), Peirce and Currence (1959), who also reported that the S.C.A. values were larger than those f o r G.C.A. although t h e i r p a r t i t i o n i n g o f the l i f e cycle was d i f f e r e n t from the present work andddid not include plastochrons. In the warm regime, f r u i t weight and f r u i t diameter both had s i g n i f i c a n t values f o r G.C.A. only (Table 23), whereas i n the cool regime both the G.C.A. and S.C.A. were s i g n i f i c a n t . Also under both temperature regimes, the estimates of S.C.A. were both much lower than those f o r G.C.A. ind i c a t i n g the f r u i t weight and diameter were largely controlled by additive gene action. This r e s u l t was not the same as that obtained by Khalf-Allah (1970), who reported that f o r f r u i t s i z e , G.C.A. and S..G.A. showed approximately s i m i l a r values. Although the same data from the d i a l l e l crosses were used i n each of two diff e r e n t a n a l y t i c a l procedures, the methods are not alte r n a t i v e s , but rather means to extract d i f f e r e n t genetic information. The Hayman-Jinks method provided several parameters and estimators which were based on data from parents and t h e i r F1 generations, and which could be used as prediction values f o r selecting among superior l i n e s . Thus a large number of l i n e s could be selected at an early generation, possibly the F 2, and the unpromising l i n e s could be 115 discarded, allowing breeders to concentrate on a r e l a t i v e l y few l i n e s with the expectation of rapid achievment of the breeders' objectives. As already indicated t h i s evaluation procedure might w e l l be adequate f o r many breeding programmes, including the ijnprovement of earliness i n tomatoes. The second analysis, G r i f f i n g ' s method provided information on the combining a b i l i t i e s of a l l parental l i n e s i n the d i a l l e l cross. There i s an estimate of the importance of additive and dominant gene action, which may be of great value to the plant breeder when he has to estimate the progeny segregation range i n order to decide on the size of the population required, and also to predict the progeny phenotypic values. As pointed out i n the , l i t e r a t u r e review, the Hayman-Jinks technique was concerned with the gene l e v e l whereas G r i f f i n g ' s method was concerned with the gametic l e v e l . In 'Other words, the G r i f f ing method can be regarded as the combination of gene interactions of the 2 genomes i n the zygote. Thus the Gr i f f i n g ' s analysis regarded the genotypical e f f e c t of an i n d i v i d u a l as the combination of effects contributed by each gamete and the in t e r a c t i o n of gametes, whereas Hayman-Jihks regarded the gene effect which may di r e c t the phenotypic expression. The plant breeder may view the G r i f f i n g method as a 'testing' procedure to study and compare the performances of parental l i n e s i n hybrid combination, and the Hayman-Jihks method indicates the genetic characteristics of the parental l i n e s . The plant breeders should keep i n mind that there are d i f -ferent contributions from both methods, and i d e a l l y any d i a l l e l cross experiment should employ both methods to help plant breeders to ' ~ -u'i^.^u'jaHtativs characters i n order t,o*£.J>:i* -116 select any quantitative characters i n order to achieve the goal. Reciprocal Cross Experiments, There /were different responses i n some growth stages i n the reciprocal crosses at the 2 temperature regimes i n the greenhouses. In the warm regime, there were no s i g n i f i c a n t differences between reciprocals (Table 26) so f a r as earliness could be measured. Ap-parently the i d e n t i c a l nuclear genes of the reciprocals controlled the growth, and differences imcytoplasm had l i t t l e i f any ef f e c t . The responses i n the cold temperature regime (Table 26) showed that Stages 1, 3 and 4 were affected by the cytoplasm which parent B con-tr i b u t e d , and these stages took longer to develop than i n the hybrid where I had contributed the cytoplasm. Although the Tl hybrids had the same nuclear gene constitution, there i s apparently a cytoplasmic-genic interaction such that cytoplasm from B under cool temperatures provides an unsuitable condition f o r thesexpression of the genes contributed by both parents to the rec i p r o c a l hybrids. Thus under the stress of cooler conditions, the cytoplasm appeared to have some importance, and t h i s i s of p a r t i c u l a r i n terest when there i s every probability that future greenhouse growers w i l l either wish or be required t o produce crops with minimum use of f u e l f o r heating. The means f o r earliness f o r tiheireciprocaiksbihhbQth:..temperature regimes i n a l l the stages, with only the one exception of Stage 5, cool, showed a tendency to be closer to the e a r l i e r parent I. These resu l t s suggest that the nuclear genes were more important i n con-t r o l l i n g plant growth than the cytoplasmic contribution which was of l i t t l e importance f o r growth except under a stress condition. These 117 r e s u l t s were somewhat dif f e r e n t from those of Shumaker et a l . (1970), who concluded that most differences between r e c i p r o c a l Fj's f o r e a r l i -ness showed matroclinous tendencies. Possible cytoplasmic differences could be associated with v a r i a t i o n i n chlorophyll content as r e f l e c t e d by net photosynthesis rates. The measurement of these rates i n the growth chamber Experi-ment I I showed the following trends. Differences i n the net photo-synthesis rates of parents B and I were not s i g n i f i c a n t u n t i l the plants had reached the 6th plastochron and then rates were s i g n i f i -cantly d i f f e r e n t through to the 8th plastochron at the end of the experiment (Table 27). This response was s i m i l a r i n both temperature regimes. The re c i p r o c a l hybrids showed fewer differences than the par-ents , and the differencesvower^ssignxf-ieahttat the 5th and 8th p l a s t o -chrons i n the warm regime and only at the 5th plastochron i n the cool regime.. The small proportion (3 out of 10 comparisons) of s i g n i f i -cant differences between reciprocals suggests that the cytoplasmic influences or effects are hardly large enough to concern the plant breeder. I t i s notedthat i n spite of the non-significant differences, there i s a trend (only one exception out of 10 comparisons) f o r the I cytoplasm of IB hybrid to be associated with higher net photosyn-thesis rates than i s the case for the reciprocal B l which.has the B cytoplasm. This apparently small contribution by the cytoplasm i s i n general agreement with the evidence presented by Levine (1969), McGinnis and Taylor (1961), Chang and Sadanage (1964) and Izhar and Wallace (1967), who have pointed out that the production of chloro-p h y l l , although located i n the cytoplasm, i s controlled by nuclear genes. 118 As shown i n Fig. 25 and 26, the net photosynthesis rate f o r a l l the l i n e s fluctuated from the 4-th to 8th plastochrons. The f l u c -tuation of net photosynthesis rate could be related t o the develop-mental phaseoof the plant. There are several reports regarding the effects of f l o r a l d i f f e r e n t i a t i o n on photosynthesis rate. Duncan and Hesketh (1968) using com, Forsyth and H a l l (1965) with blueberry, and Richardson (1967) using cotton, a l l reported that when f l o r a l d i f f e r e n t i a t i o n was occurring, there was a decrease i n the net photo-synthesis rate. In -the tomato when the reproductive phase i s under-way, there can be retardation i n the vvegetative growth (Krausy and K r a y b i l l , 1918), and t h i s retardation of vegetative growth may affect the photosynthesis r a t e , as reported by Sweet and Wareing (1966). In the present experiment, under the warm temperature regime (Fig. 25), the photosynthesis rate decreased i n c u l t i v a r B from the 5th plasto-chron, and t h i s decrease may be associated with the f l o r a l d i f f e r -e n tiation which took place from t h i s plastochron age. S i m i l a r l y the results of the d i a l l e l cross i n growth chamber Experiment I suggested an association of decreased net photosynthesis rate and f l o r a l d i f f e r -e n tiation i n c u l t i v a r C. Considering the leaf area i n both temperature regimes, (Table 28), there were differences between the two parents B and I , (I having the smaller leaf/area) which were a l l s i g n i f i c a n t except f o r the fourth plastochron i n the warm regime. None of the d i f f e r -ences between reciprocals were s i g n i f i c a n t except those f o r l e a f areas i n the 7th and 8th plastochrons i n the cool regime, which i n -dicated that the cytoplasmic differences between these two reciprocals 119 had a s l i g h t effect on the le a f area, whereas the s i g n i f i c a n t d i f f e r -ences between I vs. IB and B vs. B l indicated the nuclear genes were the major control f o r l e a f area development. From the r e s u l t s of t h i s r e c i p r o c a l cross experiment, i t may be concluded that under normal growing temperature regimes, the cytoplasmic effect was not as important as the nuclear e f f e c t ; how-ever, under stress cool temperature conditions, the cytoplasmic, ef-fect may reveal some importance especially f o r the earliness of several growth component stages. I t .is advisable therefore, that cytoplasmic effects and genie-cytoplasm interactions be studied and c a r e f u l l y con-sidered by plant breeders working on selection f o r earliness under stress temperature conditions. F i e l d Selection Experiments The f i e l d Experiments I - I I I dealt with selection and the search f o r evidence of recombination among the short growth stages. Early generation selection and t e s t i n g have been reported as p a r t i c u l a r l y suitable f o r evaluating such a crop as•the tomato (Khalf-Allah and Peirce, 1964). Peirce and Currence (1959) had con-cluded that early t e s t i n g f o r quantitatively inherited characters, such as earliness, was of d e f i n i t e value i n improving tomato plant performance. In the present f i e l d experiments, pedigree selection was started i n the F 3 f o r Stages A and C (as defined on page^3'5) and the top 6% and 11% were selected from recip r o c a l populations IB and B l respectively. In the F^ generation, the means f o r both recipr o c a l populations did not exceed the mean of the e a r l i e r parent I. The h e r i t a b i l i t i e s f o r the earliness characteristics i n the FL, 120 f o r both reci p r o c a l populations were r e l a t i v e l y high, and higher i n Stage A than i n Stage C. These h e r i t a b i l i t y differences indicated that Stage A w i l l respond to selection f o r earliness more e f f i c i e n t l y than w i l l Stage C. The t h e o r e t i c a l l y expected selection progress, AG, i n the IB population was 6.3 days f o r Stage A and 3.4 days f o r Stage C (Table 31); whereas i n the BI population, these values were 9.6 days f o r Stage A and 5.4- days for Stage C. These selection pro-gress values do not mean that the following generation w i l l be im-proved f o r earliness exactly as calculated, but these values show the r e l a t i v e tendency that, under the selection i n t e n s i t y employed, the population means w i l l be sh i f t e d i n ' the expected d i r e c t i o n by a certain amount. In selection-work, the genetic progress, aG, i s less than selection progress, AG, althbuglBtheyuareihighiliy correlated with the h e r i t a b i l i t y , h 2 , (Pirchner, 1969). In the F^ generation of the tomato selection experiment (Table 31), the genetic progress was c a l -culated as 4.6 days i n Stage A and 2.6 days i n Stage C for the IB population; and 6.2 days i n Stage A and 3.8 days i n Stage C f o r the BI population. This genetic progress indicated that under the s e l -ection i n t e n s i t y employed, the genotypic value f o r earliness w i l l be changed i n the expected d i r e c t i o n i n the F 5. Pedigree selection was continued i n the F 4 and the top 10% of early plants was selected again from both r e c i p r o c a l populations. The means of the F 5 mass populations (which were from;selected F 4 plants) were e a r l i e r than both o r i g i n a l parental c u l t i v a r s (Tables 33 and 34). These e a r l i e r F 5 population means indicated that 121 recombination of some genes f o r earliness had occurred. Although the means f o r the F 5 r e c i p r o c a l populations IB and B l were e a r l i e r than o r i g i n a l parents I and B, there were differences i n the behaviour of reci p r o c a l l i n e s . Within the mass population of IB F 5, the standard deviation was 1.6 f o r Stage A (Table 33) and 2.3 f o r Stage C (Table 34), and both these values were smaller than s i m i l a r values f o r the F^ generation, in d i c a t i n g that the segregation i n the F 5 of the IB pop-ulation had been reduced. On the other hand, i n the B l population F 5, both the standard deviations f o r Stages A and 'C were larger than those;':for the F^, and t h i s comparison indicates that segregation was continuing. Al^inggi' the F 5 population mean for each of the rec i p r o c a l hybrid populations was earlier than the mean of each of the o r i g i n a l parents (Tables 33 and 34).5 F 5 plants demonstrated that recom-bination of genes f o r earliness had occurred. The F 5 r e c i p r o c a l hybrid populations were apparently not i d e n t i c a l . The standard de-v i a t i o n f o r IB F 5 population i n both Stages A and C showed a reduc-t i o n from the IB F 4 value, however the B l F 5 population had a s l i g h t l y larger standard deviation than the B l F^. These standard deviations indicated that the segregation i n IB F 5 had been reduced whereas i n the B l F 5 segregation was continuing and producing a wider range of segregates. I t i s suggested that mass selection can be continued i n the IB population to maintain or increase the earliness, but pedi-gree selection should be applied to the B l population to observe further segregations which should allow increased chances f o r more desirable recombinations f o r earliness to appear. 122 The several experiments showed that d i f f e r e n t c u l t i v a r s proceeded through various growth component stages at diff e r e n t rates. Genetic parameters and estimators were characteristics which: f r e -quently indicated d i f f e r e n t i a l genetic behaviour i n each of two d i f -ferent temperature regimes, and among these c h a r a c t e r i s t i c s , high h e r i t a b i l i t i e s were calculated f o r earliness i n the more important or lengthy growth stages. These characteristics were used to choose parental l i n e s and to employ early generation selection. The F^ generation selection i n two rec i p r o c a l cross populations provided a good example of the r e s u l t s of early generation selection to obtain recombination of genes from two parents to produce plants ( i n F 5) which had the shortest growth Stages A and C and which were e a r l i e r than either parent. This increased earliness of some recombinations provides an example of the po t e n t i a l success to be gained from using shorter component stages from many diff e r e n t parental c u l t i v a r s to obtain recombinations which would achieve the objective of breeding f o r earliness to adapt the tomato to short and cool growing seasons i n Canada. 123 SUMMARY The inheritance of 7 growth component stages and other physiological characteristics i n tomatoes was studied i n (a) d i a l l e l crosses among 3 c u l t i v a r s , Bonny Best, Immur P r i o r Beta and Cold Set; and (b) recipr o c a l crosses between 2 c u l t i v a r s , I and B. These exper-iments were conducted i n 2 temperature regimes, 10-13°C and 17-21°C. Selection was applied s t a r t i n g i n the F 3 through to the F 5 i n the f i e l d , toeseek evidence of genetic recombination between component stages and the response to selection f o r the earliness. Data on growth stages from the d i a l l e l crosses were sub-jected t o 2 a n a l y t i c a l procedures. The f i r s t procedure used the Jinks and Hayman (1953) model to provide parameters and estimators which i n -dicated gene action i n the several growth stages. The action r e -vealed varied among the 7 stages and between the 2 temperature ve~ gimes. . Stages d i f f e r e d as t o whether overdominance, p a r t i a l or com-plete dominance was present". The dominant and recessive a l l e l e f r e -quencies were not equal i n any stages and varied i n dif f e r e n t stages. The h e r i t a b i l i t y f o r earliness of most stages was r e l a t i v e l y high. Temperature had considerable effect on the action. The second procedure, G r i f f i n g ' s method (1956), provided an estimate o f the General XGomb'ini^ Combining Ability.,and t h e i r values d i f f e r e d s i g n i f i c a n t l y i n dif f e r e n t stages and also i n d i f f e r e n t temperature regimes i n d i c a t i n g that both addi-t i v e and dominant gene action were important i n most of the component stages, although the temperature regimes affected t h i s • a c t i o n such 124 that i n some stages i n the cool regime, the dominant action was more evident. The recip r o c a l cross experiments showed that although par^ ents had s i g n i f i c a n t differences i n most of the component stages i n both temperature regimes, t h e i r reciprocal cross progeny showed no si g n i f i c a n t differences among any of the component stages i n the warm regime, but showed s i g n i f i c a n t differences i n Stages 1, 3 and 4 i n the cool regime. Thus cytoplasmic differences appeared to have some importance under the stress of the cool regime. The net photosynthesis rate i n parents I and B showed s i g -n i f i c a n t differences i n plastochron ages 6 to 8 i n c l u s i v e l y , but the reci p r o c a l progenies showed s i g n i f i c a n t differences at the 5th and 8th i n the warm regime and only at the 5th i n the cool regime. The differences i n some of the genetic parameters and es-timators i n the 2 temperature regimes i n the d i a l l e l crosses, and the differences ;be"tween recip r o c a l crosses, provide knowledge to a i d the plant breeder to choose breeding procedures f o r improving the quantitative characters including appropriate t e s t i n g procedures to i d e n t i f y valuable segregants. The demonstrated effects of tempera-ture on gene action make i t important that the environmental factor be c a r e f u l l y considered i n the breeding programme. Three seasons of f i e l d experiments were used to select f o r earliness i n growth Stages A (seeding t o . f i r s t flower) and C ( f r u i t set t o ripening). Selection was done inivthe F 3, i n 2 r e c i p r o c a l cross populations, IB and BI. The Fk progenies from the selected plant had means f o r earliness which were intermediate between the parents I and B, with a consistent tendency to be closer to the 125 e a r l i e r parent. Selection was continued i n the F 4, and the means fo r the F 5 reciprocal populations were e a r l i e r than the o r i g i n a l parents. This F 5 response must have resulted from favourable recom-binations of genes f o r the quantitative characteristics of earliness i n the 2 component growth stages of the o r i g i n a l parents. 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A study of factors a f f e c t i n g earliness and mode of inheritance of t h i s character i n the tomato. Lycoper-sicon esculentum. Diss. Abst. 26B: 4159-4160.. Z e l i t c h , I. and Day, P. R. 1973. The ef f e c t of net photosynthesis on pedigree selection f o r low and high rates of photores-p i r a t i o n of tobacco. PI. Physiol. 52_: 33-37. Z i e l i n s k i , Q. B. 1948. Fasciation i n Lycopersicon. • I. Genetic'' analysis of dominance modification. Genetics 33_: 404-428. 143 APPENDIX L i s t of Appendix Tables Table Page 1. Experimental design f o r the greenhouse experi-ment I. 146 2. Temperature record during the greenhouse experi-ment I. - 146 3. Experimental design f o r the greenhouse experiment I I . 147 4. Temperature record during the greenhouse experi-ment I I . 147 5. Experimental design f o r the greenhouse experiment I I I . 148 6. Temperature record during the greenhouse experi-ment I I I . 148 7. :;llf©isinplandesigri for the f i e l d experiment I. 149 8. Experimental design f o r the f i e l d experiment I I . 149 ment I I J . • 1 150 10. Days required f o r the 7 stages i n the greenhouse experiment I i n the warm regime. 151 11. Days required f o r the 7 stages i n the greenhouse experiment I i n the cool regime. 152 12. Days required f o r stages 5 and 6 i n the greenhouse experiment I I i n the warm regime. 153 13. Days required f o r stages 5 and 6 i n the greenhouse experiment I I i n the cool regime. 153 14. Days required per plastochron i n the greenhouse experiment I I i n the warm regime. . 154 15. Days required per plastochron i n the greenhouse experiment I I i n the cool regime. 154 144 Page 16. F r u i t weight (g) and f r u i t diameter (mm) i n the green-house experiment I I under two temperature regimes. 155 17. Days required f o r stages i n the greenhouse experiment I I I i n the warm'regime. 156 18. Days required f o r stages i n the greenhouse experiment I I I i n the cool regime. 157 2 19. Net photosynthesis rate (mg CC^/ dm /hr) i n the growth chamber experiment I I i n the warm regime. 158 2 20. • Leaf area (cm ) i n the growth chamber experiment I I i n the warm regime. 158 2 21. Net photosynthesis rate (mg CC^/dm /hr) i n the growth chamber experiment I I i n the cool regime. 159 2 22. Leaf area (cm ) m the growth chamber experiment I I i n the cool regime. 159 23. Days required f o r stages A and C i n the f i e l d experi-ment I , part 1. 160 24. Days required f o r stages A and C i n the f i e l d experiment I I . 161 145 Table 1. Experimental design f or the greenhouse experiment I. Block 1 CB BC I IB C B~ CI BI IC Block 2 BC I IC CI B BI C IB CB Block 3 B CI BC CB IB I BI IC C Block 4 C BC CB I BI CI B IB IC Table 2. Temperature record during the greenhouse experiment I. date warm cool Oct.26-Nov.3 17.2 10.0 Nov.3-Nov.10 18.3 10.6 Nov.10-Nov.17 17.8 13.3 Nov.17-Nov.24 17.2 13.9 Nov.24-Dec.l 17.2 13.9 Dec.l-Dec.8 17.2 12.8 Dec.8-Dec.15 17.2 12.8 Dec.15-Dec.22 17.8 12.8 Dec.22-Dec.29 17.2 12.8 Dec.29-Jan.5 17.2 13.9 Jan.5-Jan.12 17.8 13.3 Jan.12-Jan.19 17.2 12.8 Jan.19-Jan.26 17.2 13.3 Jan.26-Feb.2 16.7 12.8 Feb.2-Feb.9 16.1 11.7 Feb.9-Feb.16 16.1 11.7 Feb.16-Feb.23 16.1 11.7 Feb.23-Mar.2 16.7 12.8 Mar.2-Mar.9 16.7 12.2 Mar.9-Mar.16 12.8 Mar.16-Mar.23 12.8 Mar.23-Mar.30 12.8 Mar.30-Apr.6 12.8 Apr.6-Apr.13 12.8 Apr.13-Apr.20 12.8 Apr.20-Apr.27 12.8 average temperature d a i l y , C. 146 Table 3. Experimental design for the greenhouse experiment I I . Block 1 CI B IC IB C CB BI BC I Block 2 C IB I BI B CB IC BC CI Block 3 C •B BC CI BI IC I CB IB Block 4 CB C I IB BC B CI BI IC Table 4. Temperature record during the greenhouse experiment I I . date warm cool Nov.l-Nov.8 16.7 12.8 Nov.8-Nov.15 17.2 12.8 Nov.15-Nov.22 17.8 12.2 Nov.22-Nov.29 17.8 12.2 Nov.29-Dec.7 17.8 12.8 Dec.7-Dec.14 17.8 12.8 Dec, 14-Dec. 21 20.0 14.4 Dec. 21-Dec.28 18.3 11.1 Dec.28-Jan.4 17.8 13.3 Jan.4-Jan.ll 18.9 12.2 Jan.11-Jan.18 17.8 12.2 Jan.18-Jan.25 18.9 12.2 Jan.25-Feb.l 17.8 12.2 Feb.1-Feb.8 17.2 13.3 Feb.8-Feb.15 17.8 12.2 Feb.15-Feb.22 17.2 12.2 Feb.22-Mar.l 17.8 11.7 Mar.1-Mar.8 17.8 11.1 Mar.8-Mar.15 17.8 12.2 Mar.15-Mar.22 16.7 11.7 Mar.22-Mar.29 13.3 Mar.29-Apr.5 12.8 Apr.5-Apr.12 12.8 Apr.12-Apr.19 12.8 average temperature d a i l y , C. 147 Table 5. Experimental design for the greenhouse experiment III. Block 1 Block 2 Block 3 Block 4 Block 5 I B Bl IB I IB Bl B Bl I B IB B Bl I IB IB B I Bl Block 6 Block 7 Block 8 Block 9 Block 10 B Bl I IB Bl IB I B I B Bl IB IB I Bl B I Bl B IB Table 6. Temperature record during the greenhouse experiment III. date warm cool Oct.29-Nov.8 21.1 15.6 Nov.8-Nov,15 21.7 15.6 Nov.15-Nov.22 20.0 16.1 Nov.22-Nov.29 18.3 12.8 Nov.29-Dec.6 17.8, 14.4 Dec.6-Dec.13 17.8 12.2 Dec.13-Dec.20 17.8 13.9 Dec.20-Dec.27 17.2 12.2 Dec.27-Jan,3 17.2 12.2 Jan. 3-Jan..10 17.2 12.2 Jan.10-Jan.17 17.8 11.7 Jan.17-Jan.24 17.2 13.9 Jan.24-Jail. 31 16.7. 11.7 Jan.3lTFeb.7 17.2 11.1 Feb.7-Feb.14 17.8 11.7 Feb.14-Feb.21 17.2 12/2 Feb.21-Feb.28 16.1 12.2 Feb.28-Mar.6 16.7 11.1 Mar.6-Mar.13 16.7 12.8 Mar.13-Msr,20 13.9 Mar.20-Mar.27 12.2 Mar.27-Apr.3 13.3 Apr.3-Apr.10 13.3 Apr.lO-Apr.17 13.3 Apr.17-Apr.24 12.8 Apr.24-May.l 12.8 May 1-May 6 16.7 average temperature d a i l y , C. 1 4 8 Table 7. Planting plan for the f i e l d experiment I. B BIF BIxI BIxB Every represents one plant Table 8. Experimental design for the f i e l d experiment II. plot Block plant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 1 2 3 4 5 LO O O LO OS CM CO CM rH CO rH rH CM LO VD CN rH CM CO CO 1 rH 1 pq 1 LO 1 rH 1 CM | 1 1 1 CO M 1 M PM H 1 H 1 H 1 H H H H 1 M H M H rH H H rH M pq M H M H H H VD LO O LO CO o> CM CO O rH CO CN LO CM CN CO rH 00 CN CO LO rH VO 1 1 rH 1 1 1 1 1 1 CO 1 1 <M i H H 1 rH HH H H rH i H 1 M H | H H H H M H rH rH M M pq H H M H H H CO LO CO Csl vO O O LO LO CN CM oo CO VD CM <f rH H rH LO rH CO CM 1 1 1 <t 1 CM 1 1 1 rH 1 1 LO 1 PQ rH H H H I H 1 M H H 1 H rH 1 H 1 H H H M M H H H H M H H M M H H OOco CD L O i n W - i H I I - I I, H H H H - . H 1 2 3 4 5 mpQLn H H H r-i i 2 3 4 5 CO c o , r - H CO . I I H PQp ' H H 1 2 3 4 5 CO LO CO O O LO VD as CO 1 00 CM 1 VO CM LO 1 LO 1 rH rH rH 1 pq CO CO CO 1 rH 1 CM rH rH 1 rH LO H 1 rH 1 H H 1 H PH 1 H H 1 H 1 H H H H H H H H H H M M M M M pq C M . C M p v i C N zt I I I H ' , H H H i ; H H 1 2 3 4 5 CO CO O LO OS CN LO vO CO U0 00 rH CN CN <f rH CO CN rH CN CO rH CN 1 1 i 1 rH 1 1 1 CO pq | LO 1 1 rH 1 M H M 1 H H H 1 H 1 H H 1 H H H H H H M H H M M rH M H H H O *• CD LO " rH I I H H H H CQ 'I' from IBF 3; 'II' from BIF 3 149 Table 9. Planting plan for the f i e l d experiment III.' Line Rep. IB;^Fr PM pq pq Bl F r H CM n -o-m vor--oo i l l I I l i t L O L O L O L O L O L O L O L O every represents one plant 150 Table 10. Days required for the 7 stages i n the greenhouse experiment I i n the warm regime. Male H 4 - r L> C O Female parent parent B I C Replicate-1 2 3 4 1 2 3 4 1 2 3 4 1 9.5 8.8 8.7 7.9 7.0 6.3 6.4 6.3 7.0 6.9 7.1 6.4 2 • 9.2 9.4 9.1 9.0 8.3 8.6 8.5 8.5 11.7 11.5 11.5 11.5 3 33.8 34.6 31.9 30.0 22.6 22.3 23.4 21.4 20.8 23.0 19.0 18.0 B 4 21.0 23.0 23.0 20.0 21.0 21.0 20.0 23.0 19.0 17.0 16.0 19.0 5 9.1 9.0 9.3 8.6. 6.4 6.2 6.5 6.6 8.5 6.7 711 6.5 6 44.8 45.0 43.7 45.6 37.0 38.1 37.2 38.4 45.5 43.3 43.7 44.2 7 7/2 6.0 • "7,0" 6.8 5.4 4.8 5.2 5.5 5.0 5.1 5.6 5.3 1 7.3 6.5 6.6 7.4 7.6 7.3 6.8 7.5 6.3 6.3 6.7 6.0 2 8.7 9.4 9.4 9.0 9.0 8.7 9.2 9.0 L0.2 LO.O 10.1 9.9 3 20.2 22.5 19.5 23.9 18.0 17.3 15.8 18.0 19.6 18.8 17.7 18.5 I 4 17.0 20.0 21.0 23.0 19.0 17.0 19.0 19.0 17.0 18.0 17.0 19.0 5 6.6 5.7 6.4 5.2 6.4 6.8 6.0 6-:.8 6.8 6.8 6.4 6.6 6 38.3 41.1 41.0 42.4 37.0 34.2 36.1 35.9 40.5 40.0 39.8 38.9 7 4.8 5.3 5.0 5.2 4.7 5.2 4.9 5.0 4.9 4.9 5.2 5.0 1 8.0 6.3 7.6 7.0 6.0 6.4 6.3 7.0 7.8 7.0 7.3 7.5 2 9.0 8.5 8.6 8.5 9.8 9.8 11.3 9.9 9.2 9.3 9.1 9.2 3 24.2 22.7 20.6 20.0 21.8 19.7 19.2 19.7 22.8 21.7 21.9 21.8 4 25.0 20.0 18.0 20.0 17.0 17.0 17.0 17.0 27.0 20.0 23.0 21.0 5 8.4 7.5 8.5 7.8 5.6 6.3 6.4 6.5 8.6 6.3 6.7 8.0 6 45.5 46.3 46.0 45.7 37.8 39.8 41.2 40.5 45.7 48.3 49.8 48.1 7 . 5.0 •5.8 5.3 6.2 4.4 5.1 5.4 4.9 5.1 5.3 5.7 5.4 151 Table 11. Days required for the 7 stages i n the greenhouse experiment I i n the cool regime. Female parent age . Replicate  1 2 )3 -A 1 •: 2 3 (• "4 Ilk ?2 *J. '? 3., 'A 1 17.9 19.0 18.3 18.7 14.4 15.0 15.0 15.5 15.9 15.0 14.1 14.3 2 9.5 9.2 9.6 9.8 7.6 7.9 8.6 9.3 10.0 10.0 10.4 12.1 3 38.5 37.8 35.4 35.0 25.4 24.1 23.4 20.7 31.0 29.0 27.6 26.9 4 72.0 71.0 70.0 70.0 60.0 58.0 60.0 59.0 50.0 53.0 54.0 54.0 5 23.2 22.6 22.9 23.0 17.3 18.9 17.2 17.0 18.0 1*8.0 18.2 18.1 6 62.7 64.5 64.7 63.8 46.2 44.5 45.2 44.0 63.8 64.9 65.0 64.7 7 10.0 9.8 9.6 9.9 6.8 7,2 6.7 6.8 7.3 7.0 7.5 7.5 1 15.0 14.7 15.5 15.3 16.7 16.0 16.3 16.3 16.9 16.4 15.1 14.4 2 9.4 8.5 8.5 8.0 10.0 9.4 9.3 9.3 10.7 11.1 10.7 10.6 3 23.3 25.1 20.1 24.6 19.5 19.7 21.2 19.8 20.1 19.8 18.9 19.4 I 4 49.0 52.0 53.0 51.0 58.0 59.0 58.0 57.0 46.0 50.0 47.0 47.0 5 18.6 19.0 18.9 18.7 21.0 20.0 20.8 18.119.3 18.9 19.0 18.8 6 43.2 40.8 42.6 42.9 48.2 48.7 49.5 49.2 59.2 57.6 58.7 56.9 7 7.6 7.2 7.9 7.5 7.0 6.8 8.2 8.0 9.6 10.0 8.9 10.0 1 17.7 17.3 15.5 15.0 15.9 16.3 15.0 16.0 15.7 16.0 14.9 16.4 2 9.4 7.0 9.6 9.7 12.0 11.2 10.9 10.6 12.2 12.4 12.4 12.5 3 29.4 20.8 27.2 27.1 19.0 19.1 18.9 18.2 28.1 26.9 26.8 24.9 C 4 52.0 53.0 52.0 54.0 58.0 60.0 57.0 62.0 50.0 52.0 54.0 51.0 5 17.8 18.0 18.1 17.9 71.0 18.6 17.8 18.0117.9 18.0 18.6 18.7 6 64.1 65.0 64.7 65.2 58.0 62.0 56.2 57.8 52.7 53.2 52.6 53.4 7 7.2 6.9 7.0 7.3 8.6 9.2 8.2 9.0 8.1 8.6 8.0 8.4 152 Table 12. Days required for stages 5 and 6 in the greenhouse experiment I I in the warm regime. Female parent  Male B I C parent Stage Replicate 1 2 3 4 1 2 3 4 1 2 3 4 "R 5 8.0 8.0 8.0 8.0 7.0 6.0 6.0 6.0 6.5 6.5 7.0 7.0. a 6 37.0 39.0 40.0 44.0 34.5 33.5 37.0 36.0 41.0 44.5 41.5 43.0 T 5 6.0 7.0 5.5 6.0 7.0 6.0 6.5 5.5 6.0 7.0 6.0 7.0 X 6 33.5 35.0 33.0 36.0 31.0 35.0 32.0 28.0 37.0 35.0 35.0 38.5 n 5 8.0 8.5 8.0 7.5 5.5 6.5 7.0 7.0 5.5 7.0 6.0 6.0 6 41.0 36.5 38.0 39.5 34.5 35.5 39.0 39.0 44.5 42.5 40.5 46.0 Table 13. Days required for stages 5 and 6 in the greenhouse experiment I I in the cool regime. Female parent Male Stage B I C parent Replicate 1 2 3 4 1 2 3 4 1 2 3 4 B 5 7.0 7.0 6. 5 6. 0 8.0 9.0 7.5 7.0 7.5 9.0 8 .0 7.0 6 60.0 58.0 56. 5 60. 0 53.0 48.5 49.5 60.0 62.5 62.0 64 .0 63.0 T 5 8.0 7.0 8. 0 7. 0 9.0 10.0 9.0 9.0 11.0 8.5 7 .0 8.0 J_ 6 54.0 54.0 54. 0 55. 0 51.0 50.5 55.5 53.0 56.0 50.0 59 .5 56.0 r 5 7.5 9.0 7. 0 7. 0 11.0 10.0 9.5 9.5 7.5 7.5 8 .0 7.0 6 63.5 63.0 68. 0 65. 0 58.0 57.0 59.5 58.5 55.5 57.0 58 .5 60.0 153 Tabie 14. Days required per plastochron i n the greenhouse experiment II i n the warm regime. Female parent  Male B I C parent Stage Replicate  1 2 31 4 1 2 3 4 1 2A 3 4 B 1 4.5 4.4 4.4 4.3 3.7 3.7 3.8 3.7 4.0 4.0 4.1 4.2 I 3.5 3.7 3.7 3.7 3.7 3.8 3.8 3.8 4.1 4.0 4.1 4.1 C 4.0 3.7 4.0 3 .8 3.9 .3.7 4.0 4.0 4.0 4.0 4.1 4.2 Table 15. Days required per.plastochron i n the greenhouse experiment II i n the cool regime. Male parent Female parent Replicate 2;: B I C 5.9 5.9 6.0 6.1 5.4 5.9 6.1 6.1 5.4 5.3 5.5 5.6 5.4 5.4 5.1 5.3 6.0 5.9 5.9 5.9 5.9 5.9 5.6 5.5 5.8 5.7 6.2 6.1 5.9 5.8 5.5 5.7 6.5 6.4 6.0 6.1 154 Table 16,. F r u i t weight (g) and f r u i t diameter (mm), i n the greenhouse experiment II under two temperature regimes. Temperature warm cool Line Block C h a r a c t e r i s t i c s f r u i t f r u i t f r u i t f r u i t weight diameter weight diameter 1 89.5 53.5 195.3 70.0 2 102.5 58.0 200.2 76.0 B 3 93.5 56.0 186.7 68.0 4 85.6 56.0 227.8 78.0 1 22.1 34.0 27.0 37.0 2 28.4 36.5 27.9 37.5 I 3 18.2 31.5 26.2 35.5 4 18.0 33.5 32.8 40.0 1 33.3 40.0 72.9 46.0 2 47.2 44.5 44.9 44.0 BI 3 43.1 44.0 45.6 45.0 4 33.5 39.5 46.0 46.8 1 21.7 34.0 57.6 47.0 2 37.3 41.0 57.5 48.0 IB 3 52.9 48.0 59.9 48.0 4 39.0 41.0 75.0 52.5 1 47.4 45.5 80.5 c 53.5 2 72.6 51.5 78.5 53.0 C 3 67.0 48.5 80.0 53.0 4 120.0 63.0 78.5 52.0 1 il2 . . 1 59.5 92.6 57.0 2 91.0 55.0 90.3 , 55.0 BC 3 100.0 57.0 96.7 58.0 4 95.3 57.0 86.5 55.0 1 94.3 58.0 95.0 53.0 2 111.5 65.0 100.2 58.0 CB 3 50.3 44.0 101.0 58.0 4 65.2 50.0 97.3 54.0 1 25.0 36.5 58.7 49.0 2 44.3 42.5 49.4 45.0 IC 3 33.7 38.0 58.0 49.0 4 48.0 45.0 39.9 41.5 1 34.2 40.5 63.0 48.0 2 47.5 45.0 44.9 48.0 CI 3 31.9 39.0 60.2 49.0 4 48.5 45.0 52.9 46.0 155 Table \1. Days required for stages i n the greenhouse experiment I I I i n the warm regime. Replicate Line Stage 1 2 3 4 5 6 7 8 9 10 1 9 8 8 8 8 9 8 8 8 8 2 8 8 8 8 8 8 7 8 8 8 3 31 32 32 32 33 34 33 32 31 31 B 4 36 34 36 34 32- 33 31 31 : 31 30 5 7 6 7 7 6 8 8 8 8 7 6 31 32 31 31 38 41 35 35 42 40 7 9 8 9 . 10 8 17 9 10 7 7 1 8 7 8 7 7 • 7 7 7 7 7 2 6 7 7 7 6 6 6 6 7 6 3 21 20 19 19 18 18 18 19 19 19 I 4 25 25 27 22 22 23 22 24 22 31 5 5 •6 6 8 6 7 7 7 7 5 6 25 30 29 28 29 35 27 38 27 36 7 6 6"'. 5 5 5 5 7 5 6 6 1 8 7 8 7 7 7 7 7 7 7 2 6 7 7 6 7 7 7 7 6 7 3 25 24 23 25 22 25 24 25 25 25 Bl 4 . 25 25 26 26 25 24 24 25 24 25 5 6 8 8 7 7 10 7 6 5 6 6 41 27 28 30 32 40 32 27 39 30 7 7 6 5 5 4 7 6 5 5 5 1 7 8 8 7 7 7 7 7 7 7 2 7 6 7 7 7 7 8 7 7 7 3 27 27 29 27 24 23 28 26 24 25 4 23 23 24 24 25 24 24 24 24 24 5 6 8 5 5 6 7 6 7 6 7 6 29' 27 32 30 29 36 28 29 32 30 7 s: 4 44 5 6 5 6 6 6 6 c 156 Table 18. Days required f o r stages i n the greenhouse experiment I I I i n the cool regime. T . R e p l i c a t e s , Line Stage z - v = 8 9 10 1 19 21 20 21 20 20 20 20 20 20 2 •-. 9 9 9 10 11 10 10 10 9 10 3 28 30 29 30 32 30 34 31 34 34 4 65 65 66 63 64 64 64 66 67 66 5 8 10 7 8 11 10 10 9 11 11 6 59 60 59 59 60 61 61 60 59 59 7 11 9 11 12 9 8 7 9 11 8 1 2 3 4 5 6 7 18 18 16 16 17 17 17 17 17 17 10 10 9 9 10 9 9 9 9 8 20 18 19 19 20 19 8 8 19 19 22 18 49 51 51 50 53 47 47 55 51 44 11 10 8 10 10 12 12 12 52 53 53 51 53 54 54 52 48 47 11 10 8 8 13 14 BI 1 2 3 4 5 6 7 18 18 16 17 17 17 17 17 17 17 9 8 8 8 9 8 9 10 9 26 25 26 24 26 24 25 26 25 49 52 50 51 50 50 49 50 56 8 8 10 9 8 11 10 8 8 9 15 9 8 27 50 9 40 41 41 43 42 40 42 43 41 40 10 IB 1 2 3 4 5 6 7 19 17 18 19 18 18- 18 18 18 18 8 8 8 8 7 7 30 28 28 28 28 30 27 29 58 59 58 57 56* 56 57 58 57 7 8 8 50 44 44 49 41 7 9 7 10 8 8 9 28 29 57 10 10 10 9 9 38 42 42 41 40 7 9 9 T. 9 10 157 I Table 19. Net photosynthesis rate (ingCC^/dm /Kr) i n the growth, chamber experiment I I i n the warm regime. Line Rep. Plastochron 8 1 2 3 4 9.91 10V38 11.07 11.09 14.57 11.31 15.51 10.94 16.23 11.08 17.23 10.20 11.88 8.40 10.50 7.69 11.27 8.12 8.78 8.97 1 11.61 14.08 5.65 19.15 9.67 T 2 13.41 15.36 5.91 18.38 8.71 i 3 12.89 14.20 5.12 20.79 9.88 4 12.96 15.02 7.73 23.47 9.49 1 18.59 15.50 11.71 10.46 8.22 2 16.19 17.30 10.78 12.76 7.94 IB 3 17.54 14.60 11.02 9.13 8.96 4 16.31 18.59 11.24 10.28 8.33 1 17.61 13.97 10.44 6.07 6.75 2 15.59 13.38 8.55 6.99 5.65 Bl 3 14.51 14.41 8.74 7.49 6.87 4 17.65 14.21 9.97 9.25 6.56 2 Table 20. Leaf area (cm ) i n the growth chamber experiment I I i n the warm regime. Line Rep. Plastochron 8 1 2 3 4 157 85 161 236 356 68 91 151 233 375 54 101 142 252 382 70 105 162- 249 380 1 2 3 4 51 64 89 152 286 50 64 97 174 289 52 75 96 175 271 49 60 106 155 290 IB 1 2 3 4 46 85 140 247 383 39 90 152 226 389 144 101 157 249 395 43 97 140 238 400 Bl 1 2 3 4 49 88 128 259 414 43 98 133 250 404 51 91 150 239 401 46 .198 148 260 396 158 T a b l e 21. N e t p h o t o s y n t h e s i s r a t e (mgCG^/dm / h r ) i n t h e growth chamber e x p e r i m e n t I I i n t h e c o o l r e g i m e . P l a s t o c h r o n  L i n e Rep. 4 5 6 7 8 1 9.82 7.20 6.32 11.64 5.82 2 8.93 8.62 4.42 10.31 6.90 B 3 10.21 8.93 6.75 10.02 4.21 4 10.50 10.10 5.28 9.82 5.69 1 9.40 9.47 12.50 6.12 9.06 2 10.19 8.51 10.84 5.49 8.38 I 3 8.29 8.81 12.17 4.05 6.73 4 8.29 9.80 12.07 5.77 7.46 1 10.91 13.60 10.25 8.67 4.44 2 11.11. 13.17 13.02 7.75 3.71 IB 3 9.89 12.97 11.43 7.01 5.67 4 12.57 14.11 10.50 6.12 5.53 1 10.13 10.33 9.56 7.91. 3.02 2 11.23 9.82 10.80 6.69 3.72 B l , 3 9.76 8.02 11.25 9.82 .3.15 4 10.10 10.58 11.91 8.30 3.52 T a b l e 22. L e a f a r e a (cm ) i n t h e growth chamber e x p e r i m e n t I I i n the c o o l r e g i m e . P l a s t o c h r o n L i n e R e p . 4 5 6 7 8 1 64 114 159 188 220 56 116 176 186 215 B 3 58 112 170 183 209 4 52 115 162 190 211 1 34 88 112 153 184 2 36 75 120 170 192 I 3 33 82?. 115 173 189 4 44 109 116 165 190 1 50 92 159 205 246 2 46 95 169 200 237 IB 3 55 90 140 195 240 4 58 89 153 190 245 1 69 88 157 216 272 2 65 96 13.7 218 269 B l 3 52 104 160 232 275 4 54 106 168 230 280 159 Table 23. Days required for stages A and C i n the f i e l d experiment I, part 1. Line Stage Rep. I B IB)F 1 BI)F IBxI BIxI IBxB BIxB 1 72 82 74 1 77 70 72 77 82 2 70 82 74 75 69 73 78 81 3 70 79 74 74 68 70 73 72 4 70 77 74 75 71 71 76 79 5 70 81 75 76 68 71 . 77 86 A 6 71 82 80 77 72 71 76 79 7 67 80 74 72 67 71 77 79 8 69 80 71 74 71 72 82 80 9 65 80 73 73 71 71 76 80 10 71 82 73 74 66 73 76 83 11 64 82 77 71 69 74 75 76 12 68 82 74 75 70 68 78 78 1 47 56 53 51 47 50 52 55 2 46 56 46 51 47 47 52 51 3 45 58 52 52 51 47 56 51 4 41 60 54 50 47 50 56 59 5 41 58 54 51 48 50 57 55 C 6 47 57 50 49 48 51 53 •55 7 47 59 54 52 48 52 59 60 8 52 62 53 52 46 53 45 54 9 53 62 53 51 48 52 50 56 10 48 63 53 50 49 49 54 57 11 50 63 53 51 53 52 52 57 12 50 62 52 52 48 53 53 54 mc air 68. 9 160 Table 24. Days required for stages A and C in the f i e l d experiment II. „. T . Line Block Stage Line N q > 1 2 3 4 5 a e a n B : 22.2-72.4 74.4 71.8 72.6 72.7+1.7 I 63.6 63.2 63.0 63.4 63.4 63.3+0.5 1-11 1-12 I- 48 1-51 A II-2 II- 4 11-10 11-16 11-19 „ v,,.~ BI 11-22 r' " n r * n " " • 66.8±6.8 .11-25 11-33 11-35 11-50 11-53  B 54.0 56.0 56.4 57.8 55.6 56.0±3.1 _I 44.8 47.0 48.0 45.4 46.8 46.4+2.9 1-11 1-12 T—9 fi IB F - T " . - w -rw.w -r^.~ -rw.v, ,„ _ + - , ^ ^ ^  1—33 ' r r r n ^ ' "* ° ' n n I -I r\ *t —J • *t 1-48 1-51 C II-2 II-4 11-10 11-16 11-19 w -.ww -r -r^. ^ BI F -r-.~ r . -rw.- .*. ,-j -+, 7 A 11 — 22 /'"' ° / r ° ' ' ^ / r» /\ r n 11-25 11-33 11-35 11-50 11-53  each datum is the mean of the 5 plants. 69.8 71.4 69.6 69. 4 71. 6 72.8 61.8 70.3 70. 4 63. 0 63.6 62.8 64.4 63. 4 62. 4 63.8 64.0 67.6 64. 8 66. 2 73.4 68.6 57.4 64. 2 61. 6 68.2 67.2 67.4 68. 6 68. 2 62.8 64.4 66.2 72. 3 65. 8 68.8 66.0 66.6 64. 8 67. 0 63.8 69.6 66.2 64. 8 62. 6 71.3 73.2 72.0 75. 0 70. 4 63.4 66.0 67.3 67. 8 66. 2 64.2 67.2 63.2 73. 2 69.0 68.6 66.8 67.4 64. 8 69. 0 67.6 68.6 68.0 68. 6 68. 6 64.8 65.8 66.0 67. 2 66. 0 64.8 66.4 74.2 65. 8 65. 2 63.4 61.8 62.4 58. 6 61. 0 52.2 49. 8 51.2 51.4 49.4 43.6 47. 0 48.4 51.8 46.6 48.0 51. 0 46.8 45.2 48.6 46.6 53. 6 47.8 48.8 47.0 52.8 52. 2 49.2 46.2 48.8 50.0 55. 0 54.6 47.2 53.4 51.6 48. 8 50.4 48.9 50.0 45.4 54. 2 47.6 48.2 45.4 51.4 54. 4 51.8 46.2 57.4 43.8 47. 2 51.2 46.4 50.0 52.0 42  0 48 6 46.4 45 241.8 45. 8 44.6 48.0 50.0 40.6 49. 6 42.2 50.6 47.0 52.7 45. 6 49.0 46.4 53.0 43.2 45. 8 49.6 47.4 44.6 41.2 42. 2 49.0 41.6 44.4 43.2 46. 2 46.6 43.4 42.8 161 

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