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Some studies on the incidence of blothy ripening in greenhouse tomatoes in British Columbia Matsumoto, Tsutomu 1971

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SOME STUDIES ON THE INCIDENCE OF BLOTHY RIPENING IN: GREENHOUSE TOMATOES IN BRITISH COLUMBIA TSUTOMU MATSUMOTO B.S.A., Chiba U n i v e r s i t y , 1 9 6 6 A THESIS SUBMITTED IN .PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department of Plant Science We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA JUNE 1 9 7 1 i i In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree^at the University of B r i t i s h Columbia, I agree that the l i b r a r y s h a l l make i t f r e e -l y available f o r reference and study. I further agree that permission f o r extensive copying of t h i s thesis f o r scholarly/ purposes may be granted by the;head of my Department or by his representatives. I t Is understood that copying or publications of t h i s thesis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Plant Science University of B r i t i s h Columbia Vancouver 8, Canada June 1971 i i i ABSTRACT Blotchy ripening (BR) of tomatoes i s an i r r e g u l a r ripening of tomato f r u i t s . This world-wide disorder has been a problem o f the spring c r o p , , p a r t i c u l a r l y during the l a t e r part of May,; l n greenhouse tomatoes i n B r i t i s h Columbia. For the inves t i g a t i o n of the factors which a f f e c t the occurrence of BR i n B.C.,-the following were consideredi= Correlation between the hours of bright sunshine and the incidence of BR, the i n f l u e n c e ' O f weekly a l t e r n a t i o n of l i g h t and tempe-rature conditions on the incidence of BR, and the association of the incidence of BR and virus diseases. Examination of weather records led to a hypothesis;_whichi was tested i n growth chambers. The l i g h t regimes employed consisted of a high and a low l i g h t condition. Concurrently two temperature regimes,were used, one with a high maximum-temperature and the other with a low maximum temperature. Both regimes employed the same minimum temperature. The r e s u l t s of the studies were as followsJ The c y c l i c occurrence of sunny weeks and cloudy weeks was associated with the incidence of BR i n the B.C. greenhouse tomatoes. The weekly a l t e r n a t i o n of the l i g h t conditions produced 37$ BR f r u i t s when the.-.plants were subjected to a constant day-i v night temperature cycle, but only 11% BR f r u i t s , 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 6% BR i n the control, was produced when the temperature conditions were alternated simultaneously and d i r e c t l y with l i g h t regimes The role of tobacco mosaic virus (TMV) on the Incidence of BR i n the B.C. greenhouse.itomatoes did not appear to be important. The e f f e c t of potato virus (PVX) on the incidence of BR was not c l e a r . V CONTENTS Page INTRODUCTION. 1 REVIEW OF LITERATURE 3 Influence of l i g h t b Influence of temperature 5 Influence of humidity 6 Influence of s o i l moisture 7 Influence of potassium 7 Influence,;of nitrogen 8 Influence of phosphorus 9 Influence of other minerals 9 Influence of d e f o l i a t i o n 10 Influence of variety • 11 Influence of growth regulators 11 Influence of seed density 11 Influence of tobacco mosaic virus (TMV) 12 Influence of bacteria 13 Chemical nature of BR lh MATERIALS AND METHODS 1. Correlation between hours of bright sunshine and the incidence of BR 17 Data sources 17 CalculationsftofIlinear regressions 17 Significance of temperature l n r e l a t i o n to bright sunshine 20 Comparison of the incidence of BR on Vancouver Island and Lower Mainland i n 1969 21 2. The influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on the incidence of BR 21 Plant growing 21 Temperatures 22 Light 22 Combination treatments ....... 2k F r u i t harvesting 27 3 . Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia i n 1969 27 Association of BR and totato virus (PVX) .. 28 v i RESULTS Page 1. Correlation between hours of bright sunshine and the incidence of BR 30 Linear regressions between the Incidence of BR and the hours of bright sunshine 30 Significance of temperature i n r e l a t i o n to bright sunshine 36 Comparison of the Incidence of BR on Vancouver Island and Lower Mainland 36 2. The influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on the incidence of BR .. 43 3» Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia .. 54 4 . Association of BR and potato virus (PVX) 54 DISCUSSION 1. Correlation between hours of bright sunshine and the incidence of BR 6 l 2. The influence of weekly al t e r n a t i o n of l i g h t and temperature conditions on the incidence of BR .. 64 3 . Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia i n 1969 76 4 . Association ofBR and potato virus (PVX) 78 SUMMARY AND CONCLUSION' , 80 LITERATURE CITED ,j 82 APPENDIX 88 v i i LIST OP TABLES Table Page 1 S e v e r i t y of BB as recorded i n B r i t i s h Columbia f o r s p r i n g greenhouse tomato crops 18 2 Treatment regimes of l i g h t and temperature combinations 26 3 Hours of b r i g h t sunshine i n TOTAL* and FLUTO* f o r a gi v e n week of 12 cases i n Table 1 31 4 C o e f f i c i e n t of d e t e r m i n a t i o n ( i r 2 ) of l i n e a r r e g r e s s i o n of the i n c i d e n c e of BR on t o t a l hours of b r i g h t sunshine f o r weeks (TOTAL),,or accumu-l a t e d d i f f e r e n c e s i n hours of b r i g h t sunshine between c o n s e c u t i v e days f o r a week (FLUTO) 32 5 C o e f f i c i e n t of d e t e r m i n a t i o n ( r 2 ) of l i n e a r r e g r e s s i o n of the i n c i d e n c e o f BR on t o t a l hours of b r i g h t sunshine f o r weeks (TOTAL)}, or on accumu-l a t e d d i f f e r e n c e s l n hours of b r i g h t sunshine between c o n s e c u t i v e days f o r weeks (FLUTO) 33 6 C o e f f i c i e n t of d e t e r m i n a t i o n ( r 2 ) of l i n e a r r e g r e s s i o n of the i n c i d e n c e of BR on hours of b r i g h t sunshine f o r a combination of weeks (TOTAL), or on accumulated d i f f e r e n c e s l n hours of b r i g h t sunshine between c o n s e c u t i v e days f o r a combination of weeks (FLUTO) Jk 7 C o e f f i c i e n t of d e t e r m i n a t i o n ( r 2 ) of l i n e a r r e g r e s s i o n of the i n c i d e n c e of BR on t o t a l hours of b r i g h t sunshine of the week whose value of t h a t was amaximum i n the weeks of a g i v e n p e r i o d (TOTAL), or on the accumulated d i f f e r e n c e s i n hours of b r i g h t sunshine between c o n s e c u t i v e days f o r a week whose value of t h a t was a maximum i n the weeks of a given period (FLUTO) 35 8 C o e f f i c i e n t of d e t e r m i n a t i o n ( r 2 ) of l i n e a r r e g r e s s i o n of the Incidence of BR on t o t a l hours of b r i g h t sunshine of the week whose value of t h a t was a maximum in>;the weeks of a given p e r i o d (TOTAL),, or on the accumulated d i f f e r e n c e i n hours of b r i g h t sunshine between c o n s e c u t i v e days f o r the week whose value of t h a t was a minimum In the weeks of a g i v e n p e r i o d (FLUTO) 37? * See page 20 f o r d e f i n i t i o n s o f TOTAL and FLUTO v i i i Table Page 9 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR and weekly-differences of t o t a l hours of bright sunshine (TOTAL), or on weekly differences of accumulated differences i n the hours of bright sunshine between consecutive days 3" 10 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the Incidence of BR on the maximum of weekly differences of t o t a l hours of bright sunshine f o r given weeks (TOTAL), or on the maxi-mum i n the hours of bright sunshine between con-secutive days f o r given weeks (PLUTO) 39 11 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on the minimum of weekly differences of t o t a l hours of bright sunshine f o r given weeks (TOTAL),, or on the mini-mum of weekly differences of accumulated difference i n the hours of bright sunshine between consecutive days of given weeks (FLUTO) 40 12 The s i g n i f i c a n t l i n e a r regression of the severity of the incidence of BR on hours of bright sunshine 41 13 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on accumulated maximum or minimum temperatures f o r cert a i n com-binations of given weeks (TOTAL), or on accumulated differences i n maximum or minimum temperatures f o r c e r t a i n combinations of given weeks (FLUTO) 42 14 Comparison of the incidence of BR on Vancouver Island (ISL) and Lower Mainland (LM) during the period of May 14-20, 1969 44 15 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR and accumulated largest four differences i n .hours of bright sun-•shine between consecutive days f o r a week, or i t s combinations f o r three weeks 46 16 The influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on the Incidence of BR, expressed as a number of BR f r u i t s over t o t a l f r u i t s harvested 49 17 The influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on the incidence of BH In percentage 18 The Influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on theyyields of tomato crops i n grams per plant 19 The influence of weekly al t e r n a t i o n of l i g h t and temperature conditions on the f r u i t size i n grams as average f r u i t weight within a plant ... 2 0 The influence of weekly a l t e r n a t i o n of l i g h t and temperature conditions on the number of f r u i t s per plant 2 1 Association of tobacco mosaic virus (TMV) with BR f r u i t s i n commercial crops of greenhouse tomatoes i n 1 9 6 9 , 22 Results of t - t e s t on various comparison of the data l n Table 2 1 23 Presence of TMV i n f r u i t , l e a f , or l n both 2k The influence of potato virus X (PVX) on the inoidenceo-of BR 25 The influence of PVX on t o t a l f r u i t weight, per plant 26 The influence of PVX on average f r u i t weight within a plant 27 The c y c l i c occurrence of BR with l i g h t conditions alternated weekly X LIST OF FIGURES Fi gure Page 1 Daily temperature changes i n the growth chambers used f o r the BR experiments: (A) represents the temperature changes on sunny-day, and (B) repre-sents the cloudy-day 23 2 Daily l i g h t regimes f o r the contrasting l i g h t treatment used i n the BR experiments» (A) employed the high l i g h t i n t e n s i t y f o r one half of the photoperiod representing a cloudy day, (B) employed the high l i g h t f o r the entire photoperiod representing a sunny day 25 3 Hours of bright sunshine on Vancouver Island and Lower Mainland, B r i t i s h Columbia, f o r the spring (March 1 to May 31) 1969 *+5 b External and i n t e r n a l symptoms of BR f r u i t s with various degrees of severity ^8 5 The regression equation used f o r developing the hypothesis 66 6 Schematic figure of l i g h t treatment i n TcLa and TaLa conditions 66 7 Hours of bright sunshine to which the plants were exposed before being put i n chambers and corresponding expected hours of bright sunshine for the production of BR f r u i t s 70 x i ACKNOWLEDGEMENTS The author wishes to express his sincere appreciation: to Dr. C. A. Hornby f o r suggesting the problem and for his guidance, c r i t i c i s m , and patience during'.the preparation of th i s thesis. Gratitude i s also due to Dr. R. Stace-Smith, Canada Department of Agriculture Research Station, Vancouver, f o r his help i n virus assay. The h e l p f u l advice from the other members of the committee, Dr. G. W. Eaton, Dr. S. Nakai, and Dr. V. C. Runeckles, was greatly appreciated. Gratitude i s also extended to Dr. L.N. Koskitalo f o r his technical help i n operating growth chambers, and also f o r his permission to use his unpublished experimental r e s u l t s . Special thanks are due f o r many help f u l contributions of the Canada Department of Agriculture Research Station, Saanichton, and the B r i t i s h Columbia Department of Agriculture, e s p e c i a l l y the l a t t e r f o r financing the research, and arranging the survey of tobacco mosaic virus i n the commercial greenhouse tomato crops. 1 INTRODUCTION. Blotchy ripening of tomatoes i s a problem i n most, i f not a l l , parts of the world where tomatoes.are grown. This condition i s an i r r e g u l a r ripening or tissue d i s c o l o r a t i o n of tomato f r u i t s , and many d i f f e r e n t names have been used to designate the disorder; namely, blotchy ripening or BR (Bewley and White 1 9 2 6 ) , i n t e r n a l browning or IB (Haensler 194-9), gray wall (Lorenz and Knott 194-1), cloud (Kldson and Stanton 1953) and. vascular browning ( conover 194-9). As a l l these names imply, symptoms of BR may be variable. One simi-l a r i t y i n a l l cases, however, i s that a part or parts of the outer f r u i t wall are green, yellow or gray while the rest of the surface i s red. There may also be a breakdown of pericarp tissue adjacent to vascular bundles which i s r e a d i l y seen when a blotchy area i s cut transversely. A d i s t i n c t i v e l i s t and c l a s s i f i c a t i o n of BR symptoms were developed by Sadik and Minges ( 1 9 6 6 ) . Many factors Including environment, c u l t u r a l methods, and pathogens, e s p e c i a l l y tobacco mosaic ^ t r u s , have been shown to be related to the incidence of the disorder. Frequently experimental r e s u l t s have been contradictory. The occurrence of BR i n B r i t i s h Columbia has been a problem f o r greenhouse tomato growers f o r the l a s t ten years. This BR i s usually accompanied with necrotic tissue In -the spring grop, and,mos.tly i n the l a t t e r part of May. There Is also annual f l u c t u a t i o n i n the BR incidence j however, the c u l t u r a l practices used i n B?.C. have been very s i m i l a r f o r the past several years. The BB s i t u a t i o n In B r i t i s h Columbia warranted the study of, 1) the influence of weather, p a r t i c u l a r l y l i g h t , i n terms of hours of bright sunshine, on incidence of BR, and 2) the relat i o n s h i p of TMV to the incidence oof BR i n the province. The f i r s t study was intended to be a systematic examination of meteorological data to develop a hypothesis which i n turn could be tested i n controlled environment chambers. The second study was intended to ascertain the importance of TMV as a component of the BR problem i n B r i t i s h Columbia. 3 REVIEW 0? LITERATURE A large "body o f l l t e r a t u r e has accumulated since the I n i t i a l report >on blotchy ripening (BR) of tomatoes i n 1921. One of the d i f f i c u l t i e s In reviewing the l i t e r a t u r e on the disorder Is the terminology employed. Sadlk and Mlnges (1966) attempted to c l a r i f y the various observations and defined the symptoms Included, l n the blotchy ripening disorder. They presented the following c l a s s i f i c a t i o n s } A. Internal symptoms 1. White tissue characterized by the presence of areas which were off-coloured, l l g n i f l e d , and hardened, and also contained an abundance of starch, and what Is referred to as an unknown gas (Sadlk and Mlnges 1966). 2. Brown tissue resulted from the l i g n i f i c a t i o n of parenchyma c e l l walls and t h e i r ultimate breakdown and browning. B. External symptoms 1. Blotch, with or without brown t i s s u e . 2. Yellow or green shoulder. 3. Subsurface yellowing or streaks or large discolored patches. 4. Yellowing around the abscission zone. The above l i s t excludes Internal browning (IB) which i s induced by strains of tabacco mosaic virus (TMV). The tissue browning both i n BR and IB i s very s i m i l a r and i t i s d i f f i c u l t to make a d i s t i n c t i o n between the two cases (Murakishl I960, Sadik and.Minges I 9 6 6 ) . Prior to the work of Boyle and Wharton (1956), who f i r s t reported the reproduction of IB symptoms by late Inoculation of plants with TMV, there i s no mention of the presence of TMV i n plants producing BR f r u i t . Thus i n much of the l i t e r a t u r e i t i s impossible to know whether the disorder was caused by TMV i n f e c t i o n or by physiological or non-pathogenic causes. In the following review the disorder w i l l be c a l l e d by the names which appeared i n the l i t e r a t u r e under review. Although IB i s treated as a d i f f e r e n t disease i n some of the l i t e r a t u r e , i t i s included i n the present review because the IF symptoms are very s i m i l a r to those of BR; hence IB i s regarded as part of the BR problem. Influence of l i g h t Observations of annual v a r i a t i o n i n the incidence of BR from 1921-5 i n B r i t a i n , led Bewley and White (1926) to suggest climate, e s p e c i a l l y sunlight, as the causal agent. White (1938) reported a c o r r e l a t i o n c o e f f i c i e n t of - 0.803 (p=0.03) between the incidence of BR and the accumulated t o t a l of hours of bright sunlight over a five^month period. During the same period the c o r r e l a t i o n of maximum temperature and BR.vwas only 0.3^6. Clarke (19^4) noted i n a comparison of two seasons, that the lower Incidence of BR was associated with the season having the greater t o t a l sunshine. Kidson and Stanton (1953')-reported that the incidence of "cloud" varied considerably from season to season under s i m i l a r c u l t u r a l conditions. Cooper (1956) stated i n his review of l i t e r a t u r e that there was general agreement that BR had a pronounced seasonal v a r i a t i o n 5 and suggested that more detailed i n v e s t i g a t i o n of the cause of the seasonal ef f e c t would be of considerable value. Kldson (1956) suggested that shade and high humidity were "cloud" inducingj'f actors, although high humidity might not be harmful provided there was adequate l i g h t . H a l l and. Dennlson (1955) reported shading to be a contributing factor i n the occurrence of vascular browning. Murakishi (1959i 1960a) reported that the e f f e c t of low l i g h t i n t e n s i t y , was to Increase the incidence of "gray wall". In contrast to the above, Woods (1963b) obtained limited evidence that shading was e f f e c t i v e i n reducing BR. Cooper et a l (1964) experimenting with l i g h t , temperature and water supply, concluded that "shading the glasshouses reduced the proportion of non-unlformly colored f r u i t at the high tempe-rature ( 2 6 . 5 C;). At the low temperature (18.3 C), shading reduced the proportion i n i 9 6 0 but there was no e f f e c t Irr 1959". C o l l i n et a l (1965) manipulated l i g h t and temperature f o r ten day periods from flowering t i l l f r u i t ripening, but none of the treatments was e f f e c t i v e i n changing the incidence of BR. Influence of temperature Seaton (1933) determined the weekly accumulated degree hours over a base of ?0 Cand compared these values with the weekly percentage of blotchy f r u i t . He found that the percen-tage of blotchy f r u i t followed c l o s e l y the variations l n the weekly excess temperature, but there was a lag of approximately one week between the influence of temperature and the appear-ance of blotchy f r u i t . Lorenz and Knott (1941) reported 6 that "gray wall" was due to the p a r t i a l desiccation of the f r u i t wall caused by the high temperature r e s u l t i n g from d i r e c t sunshine. Jones and Alexander (1956) reported that the number of blotchy f r u i t s decreased whenplants were subjected to low temperature followed by high temperature. Under ordinary temperature conditions t h i s c o r r e l a t i o n did not hold. Woods (I965) reported that there was no consistent 1-effect of temperature on green-blotch, and that yellow blotch was unaffected by temperature. C o l l i n e_t a l (I965) subjected tomato plants to ten day periods at 50 P or ?0 F from the flowering stage u n t i l f r u i t ripening, but none of these t r e a t -ments sug&eeded i n changing the incidence of BB or IB. Lingle et a l (I965) reported a high incidence i n a growth chamber where night temperatures were low and nitrogen l e v e l was normals whereas only one or two BR f r u i t appeared on low nitrogen plants regardless of night temperature. Influence of humidity H a l l and Dennlson (1955) i n an experiment with shade, mist and s o i l compaction,, found that the high humidity produced by misting i s one of the factors contributing to the production of "vascular browning". S i m i l a r l y Proctor (I958) reported that severe BR was induced by condition of high humidity assoc-iated with high l e v e l s of watering. C o l l i n and. Cline ( I 9 6 5 ) did not f i n d any e f f e c t of high humidity on BR i n t h e i r experiments done i n controlled environ-ment chambers. 7 Influence of s o l i moisture Kldson and Stanton (1953') reported that: heavy watering increased the number of "cloud" f r u i t considerably. Taylor et a l (1958) found the si m i l a r effects f o r IB. Jones and Alexander (1962) observed that TMV- inoculated plants ;pro-duced more BR f r u i t s when plants were grown succulently with high s o i l moisture and high nitrogen. Bergman and Boyle (1966) noted an exaggerated e f f e c t of TMV i n f e c t i o n on the incidence of IB under a high s o i l moisture regime. They found high s o i l moisture increased y i e l d with larger f r u i t s i z e . Berry (1966) stated that BR appeared more frequently under conditions of low moisture stress. Woods (1963b) reported no s i g n i f i c a n t e f f e c t of s o i l moisture l e v e l on the disorder. Influence of potassium Bewley and White (1926) i n t h e i r c l a s s i c a l study of the effe c t s of mineral elements on the incidence of BR i n tomatoes stated among many findings that "BR of tomato f r u i t s Is the res u l t of malnutrition i n respect of potash and nitrogen, e s p e c i a l l y the former." Kldson and Stanton (1953.)* found that "under cert a i n conditions potassium i n excess of the standard has reduced the s u s c e p t i b i l i t y to cloud," and that " l n the early stages of the experiment the extra potassium was without apparent ef f e c t on cloud." Jones and Alexander (1956) stated that "the number of diseased f r u i t s increased as the potassium l e v e l decreaseduwhen plants were subjected to low temperatures. When plants were subjected to normal temperatures this c o r r e l a t i o n did not hold." Rich (1958),.. 8 Kidson and Stanton ( 1963) . and Winsor and Long (1967) also reported the b e n e f i c i a l e f f e c t of high potassium on reducing the incidence of the disorder. Ozbun et a l (1967) stated that "the occurrence of white tissue i n tomato f r u i t was Induced i n sand culture by low le v e l s of K." Tompkins (I963) reported that s o i l treatment with potassium sulphate and potassium chloride did not influence IB incidence. C o l l i n and Cline (1966) concluded from solution culture studies that BR did not re s u l t d i r e c t l y from the potassium deficiency but rather from the replacement of potassium by calcium or sodium. Influence of nitrogen Bewley and White (1926) stated among many findings that BR of tomato f r u i t s i s the r e s u l t of malnutrition l n respect of potash and nitrogen. There i s some evidence that high nitrogen n u t r i t i o n l e v e l s reduce BR. Kidson and Stanton (1953 ) ! found that "cloud" was reduced by the frequent app-l i c a t i o n of nltrogeneous f e r t i l i z e r . Geraldson (1964) i n his study of d i f f e r e n t sources of nitrogen, including NaNO^, N H 4 N O 3 , ( N H 4) 2S0^, Ca (N0^) 2, and KNOj, observed no r e l a t i o n of prevalence of "gray wall" to p a r t i c u l a r source materials. Lingle et. a l (I965) stated that BR or "gray wall" was almost always r e s t r i c t e d to those plants receiving nitrogen i n the nutrient solution. Only one or two BR f r u i t were noted among those from low nitrogen plants, regardless of night temperature. Cotter (1961) studied the Influence of nitrogen, potassium, boron,.and TMV on the incidence of IE and found that no treatment or treatment combinations, affected the 9 incidence of IB. Influence of phosphorus Rich ( 1958) reported on the e f f e c t s of combinations of phosphorus and potassium lev e l s and TMV, and he could not ascertain any pronounced e f f e c t s of phosphorus. Stanton (1961) reported the incidence of "cloud" or BR was greatly Increased by a heavy application of concentrated superphos-phate to the s o i l . He further reported ( I 9 6 6 ) that this increased s u s c e p t i b i l i t y to BR was f a i r l y r e a d i l y suppressed by adequate potassium and nitrogen. He suggested that high phosphate probably tends to Increase BR through i t s tendency to induce a vigorous root system and consequently a rapid growing, heavy-cropping plant. Winsor and Long ( 1967) noted that higher levels of phosphorus Increased the proportion of unevenly ripened f r u i t , and the combination of low potassium and high phosphorus had a p a r t i c u l a r l y adverse e f f e c t . Influence of other minerals Kldson and Stanton ( 1 9 5 3 ) ) reported that the application of calcium chloride to the s o i l decreased the amount of BR. Subsequently Stanton (I96I) showed that the application of lime to the s o i l increased the number of "cloud" f r u i t per plant. His r e p e t i t i o n of a s i m i l a r experiment continued t i l l 1 9 6 5 , and confirmed his previous r e s u l t s ( 1 9 6 6 ) . Mlnges and Bbutonnet ( 1966) reported no s i g n i f i c a n t differences i n occurrence of BR between high ap p l i c a t i o n of calcium and no app l i c a t i o n i n a f i e l d experiment. 10 Wlnsor and his coworkers ( 1 9 6 5 b , 1967) observed that magnesium app l i c a t i o n to the s o i l reduced the amount of BR f r u i t very s l i g h t l y , e s p e c i a l l y when compared with the e f f e c t of potassium and magnesium i n combination. Taylor (1957) used boron as a possible treatment to prevent IB and obtained favorable r e s u l t s i n one experiment but not i n another. Cotter (1961) also reported no ef f e c t from s o i l a p p l i c a t i o n of boron. Maynard et a l ( 1959) observed a marked decrease of incidence of IB as the amount of boron was lncre a s e d i i n sand culture. Tomkins ( I 9 6 3 ) reported a s l i g h t decrease i n the amount of BR when boron was applied to the s o i l . He also t r i e d f o l i a r sprays of zinc sulphate and manganese sulphate which f a i l e d to reduce the number of f r u i t s with IB s i g n i f i c a n t l y from the control. On the other hand, ferrous sulphate spray tended to reduce the incidence of BR. Influence of d e f o l i a t i o n Kidson and Stanton (1953')/ found that heavy and l i g h t pruning were associated with an increase i n "cloud". Davis et a l ( 1959) stated that severe Idefoliation resulted i n better grade f r u i t and reduced the proportion of i r r e g u l a r l y colored f r u i t , but at ;the expense of a marked reduction l n y i e l d . Cooper et a l ( 1964) observed that deleaflng had l i t t l e e f f e c t on f r u i t color except i n one experiment where the retention of a l l leaves i n June and July increased the proportion of uniformly colored f r u i t . 1 1 Influence of v a r i e t y Var ie ty differences l n s u s c e p t i b i l i t y to the disorder have been reported by many workers (Bewley and White 1926, Seaton 1 9 3 6 , Lorenz and Knott 1942, Jones and Alexander 1957, Muraklshi I 9 6 0 , C o l l i n and Wlebe i 9 6 0 , Tomkins I 9 6 3 , Cooper et a l i960,,Woods 1964a, 1965b, Fogleman 1 9 6 6 , Winsor and Long 1967). Boyle and Wharton (1957) and Cox and Weaver (1950) reported no difference among v a r i e t i e s i n the incidence of IB. No v a r i e t i e s t r i e d so f a r have been completely r e s i s t a n t to the d i s o r d e r . Using F i r e b a l l as a susceptible parent and Plant Introduct ion 235673 as a r e s i s t a n t parent, P h i l l i p (1964) reported that IB i s c o n t r o l l e d by two genes-showing compli-mentary recessive e p i s t a s i s , with l e v e l s of penetrance governed by the genotype of the p l a n t . Influence of growth regulators Tompkins (1963) found that CCC (2-chloroethy l t r i m e t h y l ammonium c h l o r i d e , a growth retardant) reduced the incidence of IB and. g i b b e r e l l i c acid tended" to increase i t . Influence of seed density Berry (1964) found that the outer w a l l t i ssue e x h i b i t i n g BR i s l o c a l i z e d over areas of low seed densi ty . He also observed that poor p o l l i n a t i o n produced a higher percentage of BR f r u i t , and these f r u i t s had a lower seed density under the blotched area. 12 Influence of tobacco mosaic virus (TMV) Bexfley and White (1926) found that acuba mosaic v i r u s , which i s a s t r a i n of TMV (Bawden 1964), caused i r r e g u l a r ripening of tomato, described as "flecks of b r i l l i a n t red or orange scattered over a s i l v e r y white background". They thought t h i s condition d i f f e r e d from the common BR which they described as green blotch on a red background. Holmes (1949) reported that he thought TMV would be associated with the incidence of IB, but his experiments f a i l e d to induce IB symptoms. Then Boyle (1956) reported the consistent repro-duction of IB by inoculation of tomato plants with strains of TMV i s o l a t e d from IB: f r u i t s . The inoculation of the <-;healthy plants was done when f r u i t s were beginning to ripen. He Interpreted the expression of IB: symptoms as a "shock" reaction r e s u l t i n g from virus Invasion. Boyle and Wharton (1957a) reported that I F symptoms were not obtained when inoculated with TMV soon a f t e r transplanting to the f i e l d . Their further i n v e s t i g a t i o n (1957b) indicated that no other kind of tomato f r u i t abnormality was produced by inoculation with TMV, and d i f f e r e n t strains of TMV may d i f f e r i n severity as shown1 by the number of blotchy f r u i t . Boyle (1959) studied TMV, tobacco rlngspot v i r u s , and cucumber mosaic virus, and reported that TMV was the only one which produced s i g n i f i c a n t l y more IB than the control plants. Lewis and Taylor (I967) demonstrated that necrotic and white tissue were induced by TMV inoculation at late plant growth. 13 Rich (1958) used TMV as one variable l n a mineral n u t r i -t i o n experiment with potassium and phosphorus. Presence of TMV gave the higher incidence of IB, but t h e v a r i a b i l i t y i n occurrence of IB over the entire harvesting period led him t o doubt that "shock" reaction was the cause. Cotter (I96I) using early and late stage inoculation with TMV, showed no e f f e c t of TMV. on the severity and incidence of BR. Jones and Alexander (1962) reported that late inoculation with TMV showed an increase l n severity and Incidence of BR. The amount of BR varied.iWith d i f f e r e n t strains of TMV. They also found a high incidence and severity of BR on plants which were TMV-free. Thus they believed that there were two d i s t i n c t diseases, namely "gray wall" or BR Induced without presence of TMV and IB induced by TMV i n f e c t i o n . Influence of bacteria When Conover (19^9) reported "gray wall" disease,a causal organism was not Isolated from diseased t i s s u e . Stoner and Hogan (1950) also concluded that the disorder was not i n c i t e d by a transmissible pathogen. Recently H a l l and S t a l l (1967a, 1967b) reported the associationiof "gray wall" with bacteria, and S t a l l and H a l l (1969) Isolated t h i r t y bacteria from "gray wall" t i s s u e . When th o s e l i s o l a t e s were injected i n t o healthy tomato f r u i t s , "gray wall" symptoms were induced. Twenty three of the Isolated species were eithe r B a c i l l u s . Erwlnla or Aerobacter. However, constant association of bacte-r i a with f i e l d occurrence of "gray wall" wasirinot established. 14 Chemical nature of BR Taylor (1957) reported that IB f r u i t s Induced by lower nitrogen and boron were lower i n reducing sugar content. S i m i l a r l y E l l s ( I 9 6 D observed lower reducing sugar content i n BR f r u i t caused by TMV. They believed that impaired trans-location of sugars caused abnormal tissue. Total sugar l n blotchy areas was also found to be lower than i n normal areas, but variable results were obtained with f r u i t s from healthy and diseased plants. Winsor and his coworkers (1958, 1959. 1962a, 1962b, 1962c) analyzed blotchy and normal f r u i t s . Their findings werei 1) Blotchy f r u i t s were lower i n dry matter, t o t a l s o l i d s i n sap, reducing sugars, t i t r a t a b l e a c i d i t y , nitrogenous compounds, potassium and e l e c t r i c a l conductivity of sap, but higher i n pH than normal f r u i t s ? 2) Blotchy tissue was lower i n t o t a l s o l i d s in;;sap, t i t r a t a b l e a c i d i t y , sugars, immersion refractometer reading and free acid, but higher l n pH and alcohol insoluble s o l i d s than normal tissue from the same f r u i t s . Values f o r these analyses f o r green blotchy tissues were between those f o r normal tissue and waxy blotch t i s s u e , suggesting that waxy blotchy i s the advanced form of green blotch* 3) Blotchy tissue was low-er i n the amount of glutamic acid, aspartic acid, pyrrolldone-carboxylic acid and c i t r i c acid, but higher l n malic acid and phosphoric acid. Prom t h e i r f r u i t analysis, they suggested that the blotchy area should be regarded as abnormal rather than merely delayed i n ripening. Davies (1966) making a s i m i l a r study, reported that both the green and red areas of blotchy tomatoes should be regarded as exceptional i n chemical c h a r a c t e r i s t i c s . 15 Hobson (1963) found that the a c t i v i t y of pectinesterase, which i s assumed to be responsible f o r s o l u b i l i z a t i o n and de-e s t e r i f i c a t i o n of pectin, rose, and there was a decrease i n content of pectic substances of the f r u i t walls as the f r u i t matured normally. However the enzyme a c t i v i t y l n blotchy areas was lower than i n the normal f r u i t j l n f a c t I t was close to the early h a l f - r i p e stage. The a c t i v i t y of polygalacturo-nase (responsible f o r the degradation of pectic substances and thus the softening of f r u i t s ) was found to Increase during normal ripening, but the increase was retarded i n blotchy areas (Hobson 1964), Kidson (1958) stated that polyphenoloxldase, an enzyme well-known f o r producing browning of f r u i t s , appeared to be responsible f o r the browning of "cloud" tissues. Healthy f r u i t - w a l l tissue when added to blotchy tissue i n v i t r o i n h i b i t e d polyphenol oxidase browning of disintegrated "cloud" t i s s u e . Ascorbic acid was very e f f e c t i v e l n preventing browning i n sus-pensions of blotched t i s s u e . C i t r i c and malic acids also had some i n h i b i t i n g e f f e c t . Glucose was e f f e c t i v e i f present in-a s u f f i c i e n t amount. High a c t i v i t y of polyphenol oxidase was observed i n green f r u i t s but the a c t i v i t y diminished with increas-ing maturity, and there was no a c t i v i t y shown by normal f r u i t s at the colouring stages. Blotched areas retained t h e i r a c t i v i t y while red parts of the same f r u i t l o s t i t . The enzyme was most active near the skin and i n the vascular system of the walls. Higher a c t i v i t y of polyphenol oxidase i n the affected areas was also reported by Hobson (1967) and Tompkins (1963) who found a s i m i l a r trend with peroxidase and cytochrome c oxidase as well. 16 Four phenolic acids l n tomato f r u i t walls were i d e n t i -f i e d "by Walker (1962) as p-coumaric, c a f f e l c , f e r u l i c and chlorogenlc acids. Except f o r p-coumaric acid, these acids were lower i n tissue from "cloud" than from-normal f r u i t at the same stage of maturation. The p-coumaric acid concentration was s i m i l a r In both f r u i t types. The deposits l n white tissue i n blotchy areas of the f r u i t were i d e n t i f i e d as l i g n i n im nature by Sadik and Minges (196) on the basis of t h e i r solu-b i l i t y and st a i n i n g reactions. They stated that l i g n i f i c a t i o m of c e l l walls occurred during early stages of f r u i t development and hence might be considered as a cause of abnormalities during ripening and coloration. 1 7 MATERIALS AND METHODS 1): Correlation between hours of bright sunshine and the Incidence of BR. Data sources Meteorological records were obtained from the University of B r i t i s h Columbia to represent the Lower Mainland climate f o r the greenhouse tomato producing area, and from the Canada Department of Agriculture Research Station at Saanichton to represent the Vancouver Island greenhouse tomato producing region. (Daily Agrometeorologlcal Data, Department of Transport, Meteorological Branch). Records were obtained f o r the years 1962 to 1969 Inclusive. The incidence of BR during that period was obtained from the reports contained l n the B r i t i s h Columbia Department of Agriculture " H o r t i c u l t u r a l News Letters". A r a t i n g system was devised to give a quantitative expression to BR described i n the weekly reports. The r a t i n g scale employed was as follows* Oi "no BR" 1» "a small amount of BR" 21 "some BR" 3« "severe BR" The newsletters only contained 12 items where the BR incidence was c l e a r l y stated and they are shown i n Table 1. C a l c u l a t i o n of the l i n e a r regressions of the Incidence of BR on  hours of bright sunshine The selected weeks l i s t e d i n Table 1 w i l l be designated hereafter as WO,.meaning the week of harvest when the occurrence 18 Table 1 Severity of BR as recorded i n B r i t i s h Columbia f o r spring greenhouse tomato crops. Severity Order Week of BR Location incidence 1. June 1-7 , 1962 2 Lower Mainland 2. May 17-23, 1963 2 Lower Mainland 3 . May 19-25. 1966 3 Vancouver Island 4. May 25-31, 1967 3 Vancouver Island 5. May 7-13, 1968 0 Vancouver Island 6. May 14-20, 1968 1 Vancouver Island 7. May 6-12, 1969 1 Vancouver Island 8 . May 14-20, 1969 3 Vancouver Island 9. May 14-20, 1969 1 Lower Mainland 10. May 24-30, 1969 3 Vancouver Island 11. June 10-16, 1969 1 Vancouver Island 12. June 17-23, 1969 1 Vancouver Island 19 of BR was reported. The week before WO wlll-be designated as Wl which means one week before harvesting. The week before Wl; w i l l be W2, and t h i s sequence continues to W? which i s the seventh week before the;-harvesting week. It was supposed that tomatoes harvested at WO would have been at or before the stage of f r u i t set at W7. .Hours of bright sunshine were summed weekly f o r WO, Wl, W2, W3, W4, W5, W6, and W7. The value of t o t a l hours of bright sunshine f o r each week ( i . e . WO through to W7) was plotted against severity of the incidence of BR which w i l l be designated as Y hereafter. As already described, the value of Y Is between 0 and 3. At the same time, l i n e a r regression, F-Ratio, r 2 , and standard error of estimate were calculated f o r each plot. Many combinations of given weeks were tested f o r co r r e l a t i o n between hours of bright sunshine and the incidence of BR. In making these combinations, the following items were tested f o r association with the incidence of BR. A. Hours of bright sunshine accumulated f o r several weeks i n a sequence. B. Hour's of bright sunshine f o r alternate weeks of sunny and cloudy conditions. C. Hours of bright sunshine f o r one p a r t i c u l a r week of a given period, which had a maximum or minimum of hours of bright sunshine. D. The difference i n the hours of bright sunshine between two consecutive weeks. E. Maximum or minimum of the difference i n the hours of bright sunshine between two consecutive weeks of a given period. 20 There were 180 combinations used i n t h i s study. The term "TOTAL" w i l l be used i n the tables of resu l t s to mean "the t o t a l hours of bright sunshine" f o r the models using weeks as l i s t e d . For example, TOTAL f o r a week which has hours of bright sunshine of 7, 8, 9, 10, 9, 6,tand y i s 52 calculated as 7+8+9+ 10+9+6+3=52. Additionally the eff e c t of d a l l y f l u c t u a t i o n i n hours of bright sunshine on the severity of the incidence of BR was considered and the d a i l y differences were summed f o r WO, Wl, W2, W3, W4, W5, W6, and W7. This t o t a l of d a i l y fluctuations of hours of bright sunshine i s abbreviated to Fluctuation Total or FLUTO. Thus FLUTO (for the week given as an example of the cal c u l a t i o n of TOTAL) w i l l be |7-H|+10, derived from f7-H|+ |8-7| + |9-8|+|10-9|+ |9-10|+|6-9| + |3-6| = |?-H|+ 10, where H i s the hours of bright sunshine of the l a s t day of the preceding week. The combinations of weeks used i n c a l c u l a t i n g TOTAL were also used to calculate FLUTO. Thus TOTAL and FLUTO values are pre-sented i n the same tables of r e s u l t s . Significance of temperatures l n r e l a t i o n to bright sunshine The combinations of weeks which were s i g n i f i c a n t l y corre-lated with the incidence of BR i n terms of hours of bright sun-shine were also used to ascertain the c o r r e l a t i o n with respect to maximum or minimum temperatures f o r those same time periods. The abbreviations TOTAL and FLUTO In t h i s case are used f o r to t a l s of maximum or minimum temperature and f l u c t u a t i o n t o t a l s of maximum or minimum temperature respectively. 21 Comparison of the incidence of BR on Vancouver Island and In  the Lower Mainland In 1969» The year 1969 showed a marked contrast i n the incidence of BR on Vancouver Island and on Lower Mainland. The week of May 14-20 on Vancouver Island showed about 3 0 - 5 0 $ BR whereas there was very l i t t l e on the Mainland. Daily hours of bright sunshine at both places were compared. The regression equations obtained from meteorological data were used l n evaluating the comparison. The d a l l y hours of bright sunshine f o r that period i n both regions were plotted. Since there were more fluctuations i n the hours of bright sunshine i n the Lower Mainland record than i n the Island record during the four days from May 8-12,-i I 9 6 9 , the p o s s i b i l i t y of the e f f e c t of the four largest d i f f e r -ences i n hours of bright sunshine within a week on the incidence of BR was investigated. 2 ) c The e f f e c t of temperatures and l i g h t on the incidence of BR. The studies of c l i m a t i c data plus some observations on greenhouse conditions l o c a l l y led to a program which was tested i n growth chambers. Plant growing The tomato plants f o r the experiment were grown and handled in:the following manner. Seed of the Early Red Chief va r i e t y was sown on February 1 0 , 1970 i n the greenhouse. One month l a t e r , the seedlings were transplanted to 9 • 6 - l i t r e p l a s t i c pots containing steam-sterilized s o i l . The plants 22 were trained to two stems. Plants were watered d a i l y with Hoagland's standard nutrient s o l u t i o n (macro nutrients only, Koskitalo 1 9 7 0 ) . A surplus of s o l u t i o n was added beyond f i e l d capacity l n order to have the excess d r a i n out of the pot, and thus preclude s a l t accumulation. On May 8 , 1 9 7 0 , plants were moved to growth chambers ( P e r c i v a l Model PGC-78 with a d i u r n a l temperature programmer ) with fou:? plants i n each of four chambers. The programmers i n the chamber employed d i f f e r e n t temperature and l i g h t c o n d i tion regimes. Temperatures The choice of temperatures was based on thermograph records from four of the tomato houses of commercial greenhouses on the Lower Mainland, B.C. Two temperature treatments were employed. Both regimes had the same minimum of 1 1 . 7 C. Maximum temperatures were 2 6 . 7 or 2 1 . 1 C. The two patterns of d i u r n a l f l u c t u a t i o n s are shown l n Figure 1. Pattern A or sunny-day temperatures with the high l e v e l of maximum temperature (26.7C) represents the conditions of a sunny day. Pattern B or cloudy-day temperature, with a low l e v e l of maximum tempera-ture represents the condition of a cloudy day. Thus the two temperature regimes were: A. Sunny-day temperature ( 1 1 . 7 C / 2 6 . 7 C, night/day) B. Alternate weeks of sunny-day temperature ( 1 1 . 7 C / 2 6 . 7 C) and cloudy-day temperature ( 1 1 . 7 C/ 2 1 . 1 C). L l crht Two l e v e l s of l i g h t i n t e n s i t y were employed to produce two l i g h t regimes. The high l e v e l of l i g h t i n t e n s i t y , 1 , 7 0 0 f-c 23 Figure 1 12 Time of Day 18 24 D a i l y temperature changes i n the growth chambers used f o r the BR experiments: (A) represents the temperature changes on sunny-day* and (B) represents the cloudy-day. 24 (foot candles) or 42 , 0 0 0 erg/cm 2/sec was obtained with sixteen 20-watt cool white fluorescent tubes and ten 40-watt tungsten lamps. For the low l e v e l of l i g h t , 990 f-c or 24 ,000 erg/cm 2/ sec,, eight fluorescent tubes and ten tungsten lamps were used. A t h i n c l e a r cellophane f i l m was used as a b a r r i e r i n the growth chambers to obtain higher l i g h t Intensity, instead of the ord-inary thick p l a s t i c sheet which gives diffused l i g h t with lower i n t e n s i t y . A photoperiod of 15 hours was used f o r both l i g h t regimes. As shown i n Figure 2 , . sunny-day conditions were obtained by using 15 hours of high i n t e n s i t y l i g h t whereas cloudy-day conditions were obtained by using 7 . 5 hours of high i n t e n s i t y l i g h t preceded and followed by 3 . 7 5 hours of low l i g h t . Thus the two l i g h t treatments were* A. Sunny-day l i g h t or 15 hours of high l i g h t i n t e n s i t y . B. Alternate weeks of sunny-day l i g h t and cloudy-day l i g h t . A l l measurements of l i g h t i n the experiment were obtained with a spectroradiometer (ISCO) which measured the l i g h t energy at the container height without plants. Light energy was calculated between 400 nm and 700 nm. These values were also converted to foot candles according to the Solar C e l l and Photocell Handbook ( 1 9 6 6 ) . Combination treatments Two temperature treatments and two l i g h t treatments were employed i n a f a c t o r i a l manner. Thus a t o t a l of four treatments were used, and they are shown l n Table 2 . 85 foot erg/cm 2/sec candles 42,000 r 1,700 Cloudy-day l i g h t (A) 24,000 - 900 •7.5 hrs--15 hrs — 0 12 18 Time of Day 24 foot erg/cm2/sec candles 42,0001-1,700 Sunny-day l i g h t (B) -15 hrs 12 Time of Day 18 24 Figure 2 Daily l i g h t regimes f o r the. contrasting l i g h t treatment used i n the BR experiments: (A) employed the high l i g h t i n t e n s i t y f o r one h a l f of the photoperiod representing a cloudy day, (B) employed the high l i g h t f o r the entire photoperiod representing a sunny day. 26 Table 2 Treatment regimes of l i g h t and temperature combinations. Treatment regime Temperature Light TcLc TcLa TaLc TaLa Sunny-day temperature Sunny-day temperature Alternate weeks of sunny-day temperature and cloudy-day temperature Alternate weeks of sunny-day temperature and cloudy-day temperature Sunny-day l i g h t Alternate weeks of sunny-day l i g h t and cloudy-day l i g h t Sunny-day l i g h t Alternate weeks of Sunny-day l i g h t and cloudy-day l i g h t In treatment TaLa, sunny-day temperature was coupled with sunny-day l i g h t , and cloudy-day temperature with cloudy-day l i g h t . 27 F r u i t Harvesting Plants were examined d a i l y and each f r u i t was dated at the time of reaching the breaker point or when any reddish color was noticed on f r u i t . F i r s t f r u i t was harvested on June 4 , 1970. Then pickings were made each week at the end of weekly treatments. F r u i t was harvested when four or more days past the breaker point. It was judged that f r u i t had developed enough color at that stage to show BR i f the f r u i t was destined to be BR. The f r u i t s were weighed i n d i v i d u a l l y . Necrotic tissue i n the affected f r u i t was recognized externally i n most cases, however f r u i t s were cut transversely and examined f o r the symptoms i n a l l doubtful cases. 3) Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia i n I969. A survey of the TMV i n f e c t i o n i n commercial crops of green-house tomatoes was car r i e d out i n 1969 i n some establishments i n the Saanichton area of Vancouver Island and Surrey i n the Lower Mainland region. The primary purpose of the survey was to ascertain whether BR f r u i t l n the B.C. crops was always infected with TMV. This survey included samples from the crop of six growers on Vancouver Island and two growers i n Surrey. The former was sampled on May 20, 1969 when severe BR was apparent, and the l a t t e r was sampled on May 25 and repeated on July 4 , 1969. 28 A f r u i t and a leaf were taken from the same plant and kept i n the same p l a s t i c bag u n t i l they were used f o r TMV assay. Nicotiana glutInosa was used as the TMV assay plant. The tomato f r u i t s and leaves were handled as follows i A piece of sampled material was placed i n a depression of a spot plate with forceps which had been dipped i n 95% alcohol and. then s t e r i l i z e d Instantly over a flame before handling each sample. A glass rod, which had both ends flattened and then roughened, was used to crush the material i n the depression of the plate. The glass rod carrying the juice was gently rubbed over the surface of a leaf of a plant of N^_ glutlnosa. The s o i l e d glass rods and spot plates were not used again u n t i l they had been washed and then s t e r i l i z e d i n a heated oven. The NJt glutlnosa plants used f o r assaying had seven to nine leaves, and four of the middle aged leaves xvere used. TMV-infected f r u i t s which had been previously assayed and a tobacco leaf which was free from TMV were used as a control. If TMV was present, the t y p i c a l l o c a l l e s i o n appeared on the leaves l n two to three days a f t e r inoculation. The r e s u l t s of the assay were noted a week or more a f t e r Inoculation. 4) Association of BE and potato virus X (PVX). Seeds of Early Bed Chief variety were sown i m bands i n the greenhouse on September 2%. 1 9 6 9 . Half of the seedlings were Infected with the virus by rubbing a young leaf with a l e a f l e t from an infected plant. The remaining untreated plants were the controls. The inoculated and control plants were moved 2 9 into 9 . 6 - l i t r e p l a s t i c containers f i l l e d with s t e r i l i z e d s o i l . The infected plants and the controls were kept i n separate green-houses. After November 17. the plants were watered d a i l y with Hoagland's standard nutrient solution (macro nutrients only).-Plants were moved into the growth chambers (Percival PG-85 with a diurnal temperature programmer) when the f i r s t three f r u i t s of the group started c o l o r i n g i . e . the end of January f o r the controls and the beginning of February f o r the infected plants. Seven PVX-infected plants were placed i n one growth chamber and seven control or virus-free plants were put i n another chamber. Seven plants of Infected and also of control plants were l e f t i n the greenhouse. The growth chamber regime was s i m i l a r to that used by Koskitalo (1970). Temperatures were 2 5 .6 :C maximum and 17.8' C minimum. The l i g h t condition was 840 f-c and 19,800 erg/cm2/sec at the container height without plants. The Virus assay was done once before and twice- a f t e r plants were placed i n the chambers. The assay procedure was the same as that already described f o r the TMV assay, except that the index plants f o r PVX were Gomphrena globosa. 30 RESULTS Do Correlation between hours of bright sunshine and the incidence of BR. Linear regression of the Incidence of BR on hours of bright  sunshine. Hours of bright sunshine l n TOTAL and FLUTO f o r a given week of 12 cases i n Table 1 are presented i n Table 3» The c o e f f i c i e n t of determination of the li n e a r regressions of the incidence of BR on the hours of bright sunshine l n B r i t i s h Columbia greenhouse tomatoes are summarized i n Tables 4 to 11. Each table presents groups of regressions as follows. Table 4 presents single weeks f o r TOTAL and FLUTO. There were no s i g n i f i c a n t c o r r e l a t i o n s . Table 5 presents accumulations of the eight weeks i n t h e i r proper sequence f o r TOTAL and FLUTO. There were no s i g n i f i c a n t c o r r e l a t i o n s . Table 6 presents many possible combination of eight weeks, p a r t i c u l a r l y a l t e r n a t i n g weeks, using accumulations, and l n some cases subtractions f o r TOTAL and FLUTO. There were some s i g n i -f i c a n t correlations with the s i g n i f i c a n t r 2 ranging from 0.3^ to 0.54. It can be seen that the highest c o r r e l a t i o n was found with the model W0+W2+W4+ W6-(W1+W3+W5+W7). Table 7 presents the models i n which one p a r t i c u l a r week of a.;given period was chosen because i t had the maximum value f o r TOTAL. There were no s i g n i f i c a n t correlations: i n these models. Table 3 Hours of b r i g h t sunshine i n TOTAL and FLUTO f o r a given week of 12 cases i n Table 1. Week TOTAL or FLUTO 12 cases WO TOTAL FLUTO 1 61.4 29. 7 2 38.3 20. 2 3 52. 7 32.0 4 42.3 29.9 5 69.9 20. 5 6 82. 7 17. 8 7 87.4 3.0 8 88. 6 14.4 9 59. 3 23. 8 10 82.9 13.9 11 50. 2 14. 2 12 32. 6 21. 2 Wl TOTAL FLUTO 47. 7 19.0 47.5 24.0 57.3 25.0 67. 8 15.4 49. 3 25. 2 88. 4 2.6 40. 2 17. 8 79.0 14.5 69.9 20. 5 75. 8 24. 7 82.9 13.9 85. 6 16.0 W2 TOTAL FLUTO 31.4 29.9 26. 6 23.0 65.3 26. 6 40.3 26.5 50.3 44.4 50.9 16.9 33. 2 20.0 44. 5 20. 1 49.3 25. 2 45. 8 24.5 75. 8 24. 7 83. 1 8. 8 W3 TOTAL FLUTO 40.2 28.4 34.5 33.9 68. 6 19. 6 41.0 43.4 51. 1 29.2 33.0 19.4 23. 7 24. 8 31.3 27. 7 50.3 44.4 65.0 9.9 45. 8 24. 5 81. 1 8.9 W4 TOTAL FLUTO 51.0 27.1 8. 8 13.0 32. 2 26.1 34. 8 28.0 30.4 33. 7 15. 6 23.9 46.0 34. 7 6.4 16.7 51. 1 29. 2 82.9 18.0 65.0 9.9 19.0 19. 8 W5 TOTAL FLUTO 30.1 28.4 25.4 13. 6 56.3 23.5 46.5 23. 7 39.2 32.3 47.4 36.6 19. 2 11.6 42.6 36. 8 30.4 33. 7 87. 4 3.0 82.9 18.0 34. 2 20. 2 W6 TOTAL FLUTO 21. 7 31.5 13.9 25.6 26.5 16.9 18.0 14.2 25.3 25. 5 27. 7 11.9 45. 7 10.2 21. 2 9.3 39.2 32.3 40. 2 17.8 87. 4 3.0 30.0 29.4 W7 TOTAL FLUTO 43.2 56.2 16.2 20.3 62.3 7.0 45. 6 40. 6 27. 6 22. 5 35. 6 10.5 48. 6 36.3 31. 6 10. 2 25.3 25.5 33.2 25.4 40.2 17.8 47. 7 29. 8 Y 2 2 3 3 0 3 1 1 1 1 3 3 Table 4 Coe f f i c i e n t of detenninaMnn (*2\ n SMIML a c c u m u l ^ e d differences i n hours "of brtSt sunshine between consecutive days f o r a week (PLUTO). r 2 f o r Week TOTAL FLUTO WO . 2 3 .28 Wl .06 . 1 3 W2 . 2 3 .28 W3 . 0 5 .02 W4 . 1 3 .00 W5 .00 .00 W6 • ! 3 .00 W7 .24 .00 No r 2 was s i g n i f i c a n t at 5 * l e v e l . 33 Table 6 Coef f i c i e n t of determination ( r 2 ) of l i n e a r regression of the Incidence of BR on t o t a l hours of bright sunshine f o r weeks (TOTAL), or on accumulated differences l n hours of bright sun-shine between consecutive days f o r weeks (FLUTO). Accumulated weeks r ^ f o r TOTAL FLUTO W0+W1 .04 . 0 2 W0+W1+W2 .00 . 0 2 WO+W1+W2+W3 .00 . 0 3 W0+W1+W2+W3+W4 . 0 1 . 0 3 wo+wi+w2+W3+w4+W5 . 0 1 . 0 1 W0+W1*W2+W3+W4+W.5+W6.' . 0 3 . 0 1 W0+W1+W2+W3+W4+W5+W6+W77 . 0 1 .00 W1+W2 . 0 6 . 2 7 W1+W2+W3 . 0 7 . 19 W1+W2+W3+W4 .00 . 1 5 W1+W2+W3+W4+W5 .00 . 0 9 W1+W2+W3+W4+W5+W6 .00 . 0 6 wi+W2+¥3+w4+W5+w6+W7? .00 .04 W2+W3 . 0 5 .14 W2+W3+W4 .00 . 1 0 W2+W3+W4+W5 .00 . 0 5 W2+W3+W4+W5+W6 . 0 1 . 0 3 W2+W3+W4+W5+W6+W7 .00 . 0 2 W3+W4 . 0 2 . 0 2 W3+W4+W5 . 0 1 .00 W3+W4+W5+W6 .04 .00 W3+W4+W5+W6+W7 . 0 1 .00 W4+W5 . 0 6 .00 w4+W5+w6c' . 1 0 .00 W4+W5+W6+W7 . 0 3 .00 W5+W6 ..06 .00 W5+W6+W7 .00 . 0 0 W6+W7 .00 . 0 0 No r 2 was s i g n i f i c a n t at 5% l e v e l . Table 6 34 Coef f i c i e n t of determination ( r 2 ) of l i n e a r regression of- the incidence of BR on hours of bright sunshine f o r a combination of weeks (TOTAL), or on accumulated differences i n hours of bright sunshine between consecutive days f o r a combination of weeks (FLUTO). Combinations.of weeks r2 fOT TOTAL FLUTO W0+W2 .08 . 0 0 W0+W2+W4 . 18 . 0 0 WO+W2+W4+W6:' .19 . 0 0 W1+W3 . 0 9 . 0 9 W1+W3+W5 . 0 2 . 0 3 WI+W3+W5+W7 . 0 7 . 0 1 W2+W4 . 0 3 .14 W2+W4+W6.' . 0 7 . 0 6 W3+W5 . 0 0 . 0 0 W3+W5+W7 . 0 5 . 0 0 W4+W6 . 1 6 . 0 0 W5+W7 . 0 2 . 0 0 W0-W1 . 2 7 . 5 2 * * W0+W2-W1 . 2 8 . 0 3 W0+W2-(W1+W3) .28 .11 W0+W2+W4-.(W1+W"3) .40 . 0 5 W0+W2+W4-(W1+W3+W5) . 3 1 . 0 3 W0+W2+W4+W6-(W1+W3+W5) . 3 8 # . 0 3 wo+W2+w4+w6-(WI+W3+W5+W7) . 5 4 . 0 2 W1-W2 . 0 0 . 0 7 W1+W3-W2 . 0 9 . 0 0 W1+W3-(W2+W4) . 2 6 . 0 0 Wi+W3+W5-(W2+W4) . 15 . 0 1 Wl+W3+W5-(W2+W4+W6) . 2 3 . 0 0 wi+W3+w5+W7-(W2+W4+W6) .40 « . 0 0 W2-W3 . 0 0 . 0 6 W2+W4-W3 .14 . 0 6 W2+w4-(W3+W5) . 12 . 0 6 W2+w4+w6-(W3+W5) . 17 . 0 2 W2+w4+w6-(W3+W5+W7) . 3 4 « . 0 3 W3-W4 .24 .00 W3+W5-W4 .14 . 0 0 W"3+W5-(w4+w6) .04 . 0 2 W3+W5+W7-(w4+w6) . 3 8 * . 0 0 w4-W5 . 1 0 . 0 1 W4+W6-W5 . 2 1 . 0 0 W4+W6-(W5+W7) .40 « . 0 0 W5-W6 . 0 7 . 0 0 W5+W7-W6 .24 . 0 0 W6-W7 . 3 7 # ..00 *i S i g n i f i c a n t at 5% l e v e l . **i S i g n i f i c a n t at 1% l e v e l . 35 Table 7 Co e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on hours of bright sunshine of the week whose value of that was a maximum i n the weeks of a given period (TOTAL), or on the accumulated differences l n hours of bright sunshine between consecutive days f o r a week whose value of that was a maximum i n the weeks of a given period (FLUTO). Weeks from which max. was chosen rd f o r TOTAL FLUTO WO, Wl .03 .12 WO, Wl„ W2 .01 .08 WO, Wl, W2, W3 .01 .06 WO, Wl, W2, W3. W4 .01 .08 W0;,.W1, W2, W3, W4, W5 .01 .04 W0, Wl, W2, W3, W4, W'5,,W6 .02 .01 wo, wi, W2, W3,,w4, W5, W6..W7 .02 .00 Wl, W2 .09 .24 Wl, W2, W3 .10 .12 Wl, W2, W3, W4 .08 .13 Wl, W2, W3, W4, W5 .06 .08 Wl, W2, W3, W4, W5, w6 .05 .03 Wl, W2, W3, W4..W5, W6, W7 .05 .00 W2, W3 .02 .15 W2, W3, W4 .00 .13 W2, W3, W4, W5 .00 .07 W2, W3, W4, W5, W6 .00 .03 W2..W3, W4, W5(iW6,,W7 .00 .00 W 3 , W4 .00 .02 W3, W4, W5 .00 .00 W3, W4, W5, W6 .00 .00 W3, w4, W5, w6, W7 .00 .00 W4, W5 .06 .02 W4, W5. W6 .06 .00 W4, W5, W6, W7 .02 .01 W5, W6 .04 .01 W5, w6, W7 .01 .01 W6, W7 .00 .00 No r 2 was;significant at 5% l e v e l . 3 6 S i m i l a r l y Table 8 presents models l n which the minimum value f o r TOTAL and PLUTO f o r the same models used l n Table 7, and again there were no s i g n i f i c a n t c o r r e l a t i o n s . Table 9 shows the systematic consideration of the difference between two consecutive weeks f o r TOTAL and FLUTO. Again there were no s i g n i f i c a n t c o r r e l a t i o n s . Table 10 shows the systematic consideration of the d i f f e r -ences of two consecutive weeks of a given period, which had the maximum value f o r TOTAL and FLUTO. There were two s i g n i f i c a n t correlations as can be seen i n the table. S i m i l a r l y the maximum values were considered, but there were no s i g n i f i c a n t correlations as shown l n Table 11. The l i n e a r regressions which had s i g n i f i c a n t r 2 are brought together i n Table 12. Significance of temperature l n r e l a t i o n to bright sunshine. Maximum and minimum a i r temperatures from meteorological records, f o r the important combinations of the weeks i n which hours of bright sunshine were s i g n i f i c a n t l y correlated with the incidnece of BR, were not s i g n i f i c a n t l y correlated with the BR incidence (Table 13). Comparison of the incidence of BR on Vancouver Island and  Lower Mainland. The severe BR present l n Vancouver Island greenhouse con-trasted with very low incidence on the Lower Mainland led to the study of the hours of bright sunshine at these two locations to t r y to elucidate the reason f o r t h i s difference. 37 Table 8 C o e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on t o t a l hours of bright sunshine of the week whose value of that was a minimum i n the weeks of a given period (TOTAL),.or on the accumulated differences l n hours of bright sunshine between consecutive days f o r the week whose value of that was a minimum i n the weeks of a given period (FLUTO). TC f o r  Weeks from which min. was chosen TOTAL FLUTO WO, , Wl .02 .00 WO, . Wl, W2 .03 .01 wo, Wl, W2, W3 .03 .03 wo, Wl, W2, W3, W4 .07 .03 wo, Wl, W2, W3, W4, W5 .03 .00 wo, Wl, W2, W3, W4, W5. W6 .01 .00 wo, Wl, W2, W3. W4, W5. w6, W7 .07 .03 Wl, W2 .02 .21 Wl, W2, W3 .06 .19 Wl, W2, W3, W4 .07 .20 Wl, W2, W3, W4, W5 .03 .08 Wl, W2, W3, W4, W5, w6 .01 .04 Wl, W2, W3, W4, W5, w6. W7 .07 .09 W2, W3 W4 .07 .09 W2, W3, .07 .02 W2, W3, W4,, W5 .03 .00 W2, W3, W4, W5, w6 .10 .00 W2, W3, W4, W5, w6, W7 .07 .03 W3, W4 .00 .02 W3, W4, W5 .04 .00 W3, W4, W5, w6 .01 .01 W3, W4, W5, w6, W7 .07 .03 W4, W5 .07 .01 W4, W5. w6 .10 .00 W4, W5, W6, W7 .07 .00 W5, w6 .06 .00 w6, W7 .02 .00 W6, W7 .09 .00 No vd was>significant at 5% l e v e l . 38 Table 9 Coef f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR and weekly differences of t o t a l hours of bright sunshine (TOTAL), or on weekly differences of accumulated d i f f e r -ences i n the hours of bright sunshine between consecutive days. Combinations Abbreviations of to be used i n r 2 f o r weeks other tables TOTAL FLUTO W0-W1 A l .00 .16 W1-W2 A2 .03 .00 W2-W3 A3 .04 .10 W3-W4 A4 .11 .00 W4-W5 A5 .02 .10 W5-W6 A6:: .00 .00 W6-W7 A7 .09 .00 No r 2 was s i g n i f i c a n t at 5% l e v e l . See the appendix f o r the actual value of A l , A2, A3, A4,. A5. A6,. and A7 f o r the 12 cases l i s t e d l n Table 1. 39 Table 10 Co e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on the maximum of weekly differences of t o t a l hours of bright sunshine f o r given weeks (TOTAL), or on weekly differences of accumulated differences i n the hours of bright sunshine between consecutive days. Weekly differences from r 2 f o r which the max. was chosen TOTAL FLUTO A l , A2 A l , A2, A3 A l , A2, A3, A l , A2, A3, A l , A2, A3, A l , A2, A3, A2, A3 A2, A3, A4 A2, A3, A4, A2, A3. A4, A2, A3, A4, A3 , A4 A3, A4, A5 A3, A4, A5, A3, A4, A5, A4, A5 A4, A5. A6 A4, A5, A6, A5. A6 A5, A6, A7 A6, A7 .00 . 0 3 .00 . 1 6 .14 . 15 .14 . 3 3 * . 0 8 . 13 .04 . 0 1 .00 . 0 6 . 2 9 . 1 0 . 2 9 . 3 5 * .17 . 13 . 1 0 . 0 1 . 0 8 . 12 . 12 .18 .14 . 0 6 . 0 7 .00 . 1 6 . 0 2 . 17 .00 . 0 7 . 0 3 .00 .00 .00 . 0 3 .00 . 0 3 * i S i g n i f i c a n t at 5% l e v e l . A l , A2, A3, A4, A5, A6 and A7 are the abbreviations shown l n Table 9 . 4 0 Table 11 Co e f f i c i e n t of determination ( r 2 ) of l i n e a r regression of the incidence of BR on the minimum of weekly differences of t o t a l hours of bright sunshine f o r given weeks (TOTAL),, or on the minimum of weekly differences of accumulated differences i n the hours of bright sunshine between consecutive days of given weeks (PLUTO).. Weekly differences from r 2 f o r which the min. was chosen TOTAL FLUTO A l , A2 .07 .28 A l , A2, A 3 .02 .03 A l , A2, A 3 , A4 .02 .04 A l , A2, A 3 , A4, A5 .01 .06 A l , A2, A 3 , A4, A 5 , A6 .00 .19 A l , A2, A 3 , A4, A 5 , A6, A7 .00 .12 A2, A 3 .00 .08 A2, A 3 , A4 .00 . 0 0 A2, A 3 , A4, A 5 .01 .00 A2, A 3 , A4, A 5 , A6 .02 .01 A2, A 3 , A4, A 5 , A6, A7 .00 .10 A 3 , A4 .02 , 0 0 A 3 , A4, A5 .00 .08 A 3 , A4, A 5 , A6 .01 .01 A 3 , A4, A 5 , A6, A7 .00 .00 A4, A 5 .03 .18 A4, A 5 , A6 .02 .05 A4, A 5 , A6, A7 .22 .03 A 5 , A6 .02 .02 A 5 , A6, A7 .24 .03 A6, A7 .31 .00 No r 2 was s i g n i f i c a n t at 5% l e v e l . A l , A2, A 3 , A4, A 5 , A6 and A7 are the abbreviations shown i n Table 9. 41 Table 12 The s i g n i f i c a n t l i n e a r regression of the Incidence of BE on~ hours of bright sunshine. Combinations of weeks TOTAL or FLUTO r 2 Cons-tant (a) C o e f f i -cient (b) Standard error of estimate W0-W1 FLUTO .52 1 .62 .0809 .765 W0+W2+W4-(W1+W3) TOTAL .40 2.43 -.0184 .854 W0+W2+W4+W6r(W1+W3+W5) TOTAL .38 2.09 -.0143 .867 W0+W2+W4+W6-(W1+W3+W5+W?) TOTAL .54 1 .51 -.016? .744 W1+W3+W5+W7-(W2+W4+W6) TOTAL .40 .446 .0170 .854 W2+w4+Wot-( W3+W5+W7) TOTAL .3* 1 .56 .0174 .897 W3+w5+W7-(w4+w6) TOTAL .38 .720 .0170 .864 W6-W7 TOTAL .37 1.60 - .0298 .874 Max.* (A1,A2,A3,A4,A5) FLUTO .33 3.82 - .1291 .900 Max.** (A2,A3,A4,A5) FLUTO .35 3.86 -.1324 .885 TOTALt FLUTO« Accumulated hours of bright sunshine f o r a week. Accumulated differences i n the hours of bright sunshine between consecutive days f o r a weeks. A maximum of A l , A2, A3, A4 and A5. A maximum of A2, A3, A4 and A5. A l , A2, A4 and A5 are abbreviations shown i n Table 9. 4B Table 13 Coef f i c i e n t of determination ( r 2 ) of l i n e a r regressions of the incidence of BR on accumulated maximum or minimum temperatures f o r certain combinations of given weeks (TOTAL), or on accumu-lated differences In maximum or minimum temperatures f o r cer-t a i n combinations of given weeks (PLUTO). TOTAL r2 f o r Combinations of weeks FLUTO or maximum temperature minimum temperature W0-W1. W0+W2+W4-(W1+W3) wo+w2+w4+w6-(WI+W3+W5) W1+W3+W5+W7-(W2+W4+W6) W3+W5+W?-(w4+w6) W6-W7 Max.* (A1,A2,A3,A4,A5) Max.** (A2,A3,A4,A5) FLUTO TOTAL TOTAL TOTAL TOTAL TOTAL FLUTO FLUTO . 1 5 . 2 0 . 2 0 . 0 8 .14 . 1 2 . 0 3 . 0 9 .00 .01 .00 .00 .00 .00 .12 .14 * Maximum of A1,A2,A3,A4, and A5. ** Maximum of A2,A3,A4 and A5. A l , A2, A3, A4 and A5 are abbreviations shown i n Table 9 . 43 It can be seen i n Table 14 that the regression of BR Incidence (Y) on the various ten models (X^....X^Q) f o r l i g h t e f f e c t s gave calculated values f o r Y which i n only the case of the Xx model closely approached the actual or known value of Yt. which was the BR incidence reported from commercial greenhouses. The X i model used i n the regression equation was Y=l.62+0.0809X, where the X was the f l u c t u a t i o n value or PLUTO f o r the combination! of the preceding harvest and harvest week (W0-W1) showed the largest Y difference between the Island and Lower Mainland, and that week showed the great difference i n the severity of BR between the two regions. Figure 3 shows that the patterns of d a i l y hours of bright sunshine f o r the Island and Lower Mainland during March to May were s i m i l a r . A marked decrease l n hours of bright sunshine can be noted for three days from May 9 to 11 i n the Lower Mainland record whereas the same period f o r the Island was a l -most constant. Significance of the l i n e a r regression of the incidence of BR and the accumulated four largest differences i n a week f o r WO, Wl, or W2 and t h e i r combinations i s summarized i n Table 15. Only the W0-W1 model was s i g n i f i c a n t ( r 2 ~ . 4 2 ) . The regression equation f o r that model i s Y=l.59+0.0887X which gives Y values of 2.03 f o r the Island and 1.54 f o r the Mainland, and these cl o s e l y approximate the values a c t u a l l y reported f o r BR incidence. 2) The influence of weekly al t e r n a t i o n of l i g h t and tempera-ture conditions on the incidence of BR. 44 Table 14, Comparison of the incidence of and Lower Mainland (LM) during BR on Vancouver Island (ISL) the period of May 14-20, 1 9 6 9 . X value f o r Corresponding Actual value Regression equation ISL LM value of Y f o r of Y f o r ISL LM" ISL LM' Y=l.62+.0809Xi 15.2 -.10 2.84 1..61 3 r Y=2 .43-.0I84X 2 27.8 29.2 1.91 I.89 3 1 Y=2.0 9 - . O I 4 3 X 3 8.10 7.80 1.97 1.98 3 1 Y = l . 51-.,0167X4 -27 .5 ^23.8 1.97 1 . 9 0 3 1 Y=.446+,0170X3 110 112 2 .31 2 . 3 5 3 1 Y=1.56+.0174X6 -21.8 -33.4 1 . 13 .982 3 1 Y=.720+.0170X? 72.7 77.9 1.95 2.04 3 1 Y=l.60-.0298X8 - 7 . 9 -10.4 I . 8 3 1 . 9 0 3 1 Y=3.82-.I29IX9 15.2 20.1 1.86 1 . 2 3 3 1 Y : = 3.86 - . 1 3 2 4 X 1 0 14 .3 20.1 1.97 1.20 3 1 Yt Xl, Xy *4: x8 x 9 Severity of the incidence of BR. 0 Y 3 FLUTO TOTAL TOTAL TOTAL TOTAL TOTAL TOTAL TOTAL FLUTO Xio * FLUTO TOTAL: FLUTO: A l , A2 fo r (W0-W1) fo r (W0=W2+W4-(W1+W3)) fo r (W0+W2+W4+W6-(W1+W3+W5)) f o r (W0=W2+W4+W6-(W1+W3+W5+W7)) f o r (W1+W3+W5+W7-(W2+W4+W6)) for (W2+w4+w6-(W3+W5+W7)) f o r (W3+W5+W7-(W4+W6)) f o r (W6-W7) f o r the maximum of ( A l , A2, A3, A4 and A5) fo r the maximum of (A2, A3, A4 and A5) bright sunshine, fluctuations i n hours of bright e e Total hours of Total of d a l l y sunshine. A3, A4 and A5 are abbreviations shown l n Table 9 . Hours 4 5 Figure 5 iiours of bright sunshine on Vancouver Island and Lower Mainland, B r i t i s h Columbia, f o r the spring (March 1 to Kay 31) 1969. 46 Table 15 Coeff i c i e n t of determination ( r 2 ) of li n e a r regression of the incidence of BR and accumulated largest four differences i n hours of bright sunshine between consecutive days f o r a week, or i t s combinations f o r three weeks. Combinations of weeks r WO .24 Wl .10 W2 .10 WO-Wl .42* W1-W2 .00 WO-Wl W2 .14 Iwo-wil .2? IW1-W2I.. .00 |W0-W1'|+|W1-W2| .14 Max (W0.W1) .20 Max (W0.W1.W2) Max (W1.W2) .03 .09 Min (W0.W1) .00 Min (W0.W1.W2) Min (W1.W2) .00 .12 *i S i g n i f i c a n t at 5% l e v e l . Max (W0.W1) means the:_inaxlmum of W0 and Wl. Min (W0.W1) means the minimum of W0 and Wl. 47 The number of BR f r u i t s produced i n t h i s growth chamber experiment varied with the treatments. A l l the BR f r u i t s had necrotic tissue i n the affected f r u i t wall. The severity of the symptoms was also variable ( F i g . 4 ) . The symptoms i n the control treatment (TcLc^) were very mild except f o r two of seven BR f r u l t s , -i . e . externally the affected area on the f r u i t did not exceed one o i ,.and i n t e r n a l l y , only vascular bundle In the affected area had a necrotic appearance. The TcLa treatment which gave the highest BR incidence produced the most severe symptoms. The affected areas of the majority of the BR f r u i t s i n that treatment exceeded 10 cmS The entire f r u i t was affected with the disorder i n some cases. F r u i t with severe BR had large i r r e g u l a r s t r i p s of necrotic tissue, and the blotchy area often had collapsed c e l l s i n the subsurface layers r e s u l t i n g i n small hollow spaces or c a v i t i e s . The severity of the BR symptoms of most f r u i t s from TaLc and TaLa treatments was somewhat intermediate between TcLc and TcLa. The incidence of BR, with degrees of severity as des-cribed above, i s shown i n Table 1 6 . Inspection of the data showed that the TcLa treatment had the highest incidence of BR which was 3 7 * 2 # of the t o t a l number of f r u i t s . TcLc treatment had a low Incidence of 6 . 1 $ BR. The Incidence l n TaLa was 1 0 . 9 # and i s also markedly lower i n BR incidence than eith e r TaLc or TcLa. It i s to be noted that the lower amounts of BR occur l n the chambers where both temperature and l i g h t conditions were either consistent or alternated simultaneously. F i g u r e 4 E x t e r n a l and I n t e r n a l symptoms of BR f r u i t s with v a r i o u s degrees of s e v e r i t y . The f i r s t p i c t u r e shows the e x t e r n a l symptoms; the second, the i n t e r n a l symptoms of the same f r u i t s . The c r o s s - s e c t i o n s of the f r u i t s were arranged so t h a t the f r o n t p a r t of the f r u i t In the f i r s t p i c t u r e i s p o i n t i n g toward the top of the page i n the second p i c t u r e . 49 Table 16 The Influence of weekly al t e r n a t i o n of l i g h t and temperature conditions on the incidence of BR, expressed as a number of BR f r u i t s over the t o t a l number of f r u i t s harvested. Length Treatment of treatment TcLc TcLa TaLc TaLa (weeks) 4 1/9 - - 0/2 5 1/13 1/1 0 /4 0/5 6 0/21 2/7 1/7 2/13 7 0/10 7/15 4/17 2/15 8 3/24 4/19 1/20 1/15 9 0/13 12/29 3/28 2/20 10 2/9 12/25 10/32 3/15 11 0/6 6/19 6/1? 1/7 12 0/6 1/4 3/H 0/7 13 0/4 0/2 - 0/2 Total {% BR f r u i t ) 7/H5 (6 .1 ) 45/121 (37 .2) 28/136 ( 2 0 . 6 ) 11/101 (10.9) 50 When the data i n Table 16 was subjected to s t a t i s t i c a l analysis, d i f f i c u l t i e s were encountered. The small size of some samples and the v a r i a b i l i t y i n number of f r u i t s harvested during ten weeks precluded the analysis of data as a binomial d i s t r i b u -t i o n . The usual recommendation of expressing such data in-per-centages also had to be rejected. When the data i n Table 16 were considered as a commercial h o r t i c u l t u r a l crop, y i e l d s could be consolidated into the four harvest groups, namelyj 1) early crops Yie l d f o r weeks k to 6 2 ) second early crops — y i e l d f o r weeks 7 and 8 3 ) main crops y i e l d f o r weeks 9 and 10 4 ) late crops y i e l d f o r weeks 11 to 1 3 . The data of Table 16 are shown l n t h i s manner i n Table 1 7 , expressed as percentages. S t a t i s t i c a l analysis showed that the i n t e r a c t i o n of l i g h t and temperature was the only s i g n i f i c a n t component of variance. Duncan's test shows that the TcLa t r e a t -ment produced a s i g n i f i c a n t l y higher percentage of BR than TcLc and TaLa treatment. The other differences i n the occurrence of BR were not s i g n i f i c a n t . Total y i e l d , f r u i t s i z e , and f r u i t number per plant were also recorded (Tables 18, 19 and 2 0 ) . The treatments TcLa and TaLc,. which resulted i n the greater percentage of BR f r u i t s , tended to have the larger f r u i t s i z e , greater number of f r u i t s per plant and therefore, greater t o t a l y i e l d . The differences are not s i g n i f i c a n t with the exception of the TaLc y i e l d r e l a t i v e to the other treatments. Table 17 The Influence of weekly alte r n a t i o n of l i g h t and temperature conditions on the incidence of BR i n percentage. Crops Treatment  TcLc TcLa TaLc TaLa % #' % < Early 4.7 37.5 9.1 10.1 2nd early 8.8 32.4 13.5 10.1 Main 9.1 44.4 21.7 14.: Late 0 . 0 28 .0 32.1 6.: Mean 5.6 b: • 35 .6 a 19.1 ab io.: Treatment means with common l e t t e r s are not s i g n i f i c a n t l y d i f f e r e n t at 5% l e v e l . Table 18 The Influence of weekly alte r n a t i o n of l i g h t and temperature conditions on the y i e l d of tomato crops l n grams of f r u i t . Treatment Plant Mean TcLc 4900 5050 3701 3143 4198. 5b-TcLa 4654 4698 4942 3850 4536.0b TaLc 4764 6339 6090 5461 5663.5a TaLa 3529 4318 3161 2674 3420.5b Treatment means with a common l e t t e r are not s i g i f i c a n t l y d i f f e r e n t at 5% l e v e l . Table 19 The Influence of weekly alte r n a t i o n of l i g h t and temperature conditions on the f r u i t size i n grams as average f r u i t weight within a plant. Treatment Plant Mean: TcLc 148.5 148.5 154.2 131.0 145.6a TcLa 179.0 134.2 164.7 128 .3 151.6a TaLc 158.2 171,3 164.6 1 7 0 . 7 l6.6.1?a TaLa 196.1 110.7 121.6 148.6 144.3a Treatment means with a common l e t t e r are not. s i g n i f i c a n t l y d i f f e r e n t at 5% l e v e l . 53 Table 20 The Influence of weekly al t e r n a t i o n of l i g h t and temperature conditions on the number of f r u i t s per plant. Treatment Plant. Mean TcLc 33 34 24 24 28 .5 a TcLa 26 35 30 30 3 0 . 3 a TaLc 30 3? 3? 32 3 4 . 0 a TaLa 18 39 26 18 2 5 - 3 a Treatment means with a common l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t at 5% l e v e l . 54 3) Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia In I969. The data i n Table 21 show that some BR f r u i t s from commer-c i a l greenhouses were free from TMV. Although BR was present l n the greenhouse of grower No.3» the plants were free from TMV. The data i n Table 21 were analyzed f o r various aspects and res u l t s are l i s t e d i n Table 2 2 . The prevalence of TMV" both i n BR f r u i t s and non-BR f r u i t s i n the two locations did not d i f f e r s i g n i f i c a n t l y . Also the prevalence of TMV among non-BR f r u i t s did not d i f f e r s i g n i f i c a n t l y between Vancouver Island and the Lower Mainland. Furthermore, the prevalence of TMV among non-BR f r u i t s l n May on the Lower Mainland did not d i f f e r s i g n i f i c a n t l y from that i n July. There were s i g n i f i c a n t l y more BR f r u i t s with TMV on the Island than on) the Mainland. The assays of TMV i n a f r u i t and a leaf from the same plant, as shown i n Table 2 3 , indicate that the presence of the TMV. was not always demonstrated i n both the f r u i t and leaf of a given plant. One extreme case Is noted f o r grower NO.8 where 33 plants were sampled, and 26 of the f r u i t showed TMV with corresponding leaves apparently free from the v i r u s . 4) Association of BR and potato v i r u s X (PVX). Virus assays showed that control plants were free from TMV and PVX throughout the experiment. The PVX-lnfected plants were infected by PVX only and not by TMV. The mosaic symptoms of PVX i n f e c t i o n appeared on the plants two months afte r the inoculation. 5 5 Table 21 Association of tobacco mosaic virus (TMV.) with BR f r u i t s l n commercial crops of greenhouse tomatoes i n 1969. F r u i t s with BR F r u i t s without BR Place Grower Total Infected Total Infected Date number with number with of assayed TMV assayed TMV sampling N0.1 10 8 2 2 NO. 2 - - 6C 2 NO. 3 7 0 8 0 ISL NO. 4 2 2 1 0 May 25/69 NO. 5 5 5 5 5 NO. 6 6 6 k k Subtotal 30 21 13 NO. 7 6 5 k 3 ray 20/69 NO.8 28 28 5 5 Subtotal 3 * 33 ~9 "8" LM NO. 7 - - 2k 23 July 14/69 NO.8 - - 36 34 Subtotal 60 57 I S L J LMI Vancouver Island Lower Mainland 56 Table 22 Results of t-te s t on various comparisons of the data i n Table 21. Differences i n frequency of TMV between; Significance BR (21/30) and non--BR f r u i t s (13/26) on ISL. N.S. BR (33/34) and non--BR f r u i t s (8/9) on LM' i n May.. N.S. ISL (13/26) and. LM. (8/9) non-BR f r u i t s i n May. N.S. ISL (21/30) and LM~ (33/34) BR'fruits i n May. « May (8/9) : and. July (57/60) i n non-BR f r u i t s on LM. N.S. Numbers i n a parenthesis show the number of f r u i t s with TMV."over t o t a l number of f r u i t s surveyed. ISL i Vancouver Island. LM'i Lower Mainland. N.S.i Not s i g n i f i c a n t .at 5fo l e v e l . * t S i g n i f i c a n t at 5% l e v e l . 57 Table 23 Presence of TMV In f r u i t , - l e a f , or i n both. T o t a l P l a c e Grower number of f r u i t s assayed both f r u i t f r u i t only and l e a f TMV present l n l e a f o n l y n e i t h e r Date of sampling ISL N0.1 13 61 5 l ;•; l NO.2 6 2 0 0 NO.3 16 0 0 0 16 NO.4 3 2 0 l 0 NO. 5 10 10 0 0 0 NO. 6 10 10 0 0 0 May 25/69? S u b t o t a l 58" 30 21 NO. 7 10 4 4 1 1 ' LM NO.8 33 7 26: 0 0 May 20/69 58 One plant only l n the experiment produced BR which had necrotic tissue i n the f r u i t wall. This observation was not s t a t i s t i c a l l y s i g n i f i c a n t because the BR was present on only two out of eight f r u i t s on one of the 14 plants i n that growth chamber series, that i s 3.3% BR f r u i t as;.shown i n Table 24. Yie l d per plant and average f r u i t weight per plant are shown i n Tables 25 and 26 respectively. The control plants grown i n the greenhouse -gave a higher y i e l d than plants i n the growth chambers. The average f r u i t weight per plant was greater under greenhouse conditions, but the presence of PVX had no s i g n i f i c a n t e f f e c t on f r u i t s i z e . 5 9 T a b l e 24 The I n f l u e n c e o f p o t a t o v i r u s X(PVX) on t h e i n c i d e n c e o f BR. P e r c e n t a g e o f f r u i t w i t h BR  Growth chambers G r e e n h o u s e s PVXr-infected 3.3 .0 PVX;free .0 .0 T a b l e 25 The i n f l u e n c e o f PVX on t o t a l f r u i t w e i g h t p e r p l a n t . P l a n t NO. Weight o f f r u i t p e r p l a n t (grams) P V X - i n f e c t e d PVX f r e e G r e e n h o u s e Chamber Greenhouse Chamber 1 1075-5 838.7 932.8 1011.8 2 610.7 513.6 755.8 725.8 3 987.5 672.2 814.7 706.4 k 630.7 979.5 509.1 1116.9 5 962.5 1093.0 1147.0 380.2 6 832.3 500.1 970.3 862.4 7 816.9 930.6 1263.5 638.0 Mean 845.2b- 789.7b 995.2a 777.4b T r e a t m e n t means w i t h a common l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t . 60 Table 26 The Influence of PVX on average f r u i t weight within a plant. • A v e r a g e f r u i t weight (grams) Plant NO. PVX-lnfected PVX free Greenhouse Chamber Greenhouse Chamber 1 119.5 9 3 . 2 116.6 101.2 2 122.1 8 5 . 6 94 .5 103-7 3 157.7 74.7 9 0 . 5 8 8 . 3 4 9 6 . 3 81 .6 72.7 101.5 5 92 .5 109.3 114.7 63.4 6 98.8 83.4 9 7 . 0 106.3 7 90.8 116.3 140.4 95.8 Mean 111.0a 9 2 . 0 a 103.7a 9 4 . 3 a Treatment means with a common l e t t e r are not s i g n i f i c a n t l y d i f f e r -ent. The analysis of variance showed that the primary e f f e c t of location was s i g n i f i c a n t at 5% l e v e l . 61 DISCUSSION 1). Correlation .between hours of bright sunshine and the incidence of BR. White (1938) observed a negative c o r r e l a t i o n between BR incidence and t o t a l hours of bright sunshine during f i v e months of the season. He attributed the annual differences i n the incidence of BR to the t o t a l hours of bright sunshine which vary annually. Data used In th i s present study suggest that the hours of bright sunshine may also be associated with the f l u c t u a t i o n of the incidence of BR within a season. Although hours of bright sunshine f o r any p a r t i c u l a r week were not s i g n i f i c a n t l y correlated with the severity of the BR incidence (Table 4), the hours of bright sunshine f o r some combinations of weeks were correlated s i g n i f i c a n t l y (Table 6). Such combi-nations, as summarized i n Table 12, suggested that weekly f l u c t u -ation of t o t a l hours of bright sunshine i s the Important i n f l u -ence of the l i g h t factor on the incidence of BR, rather than the t o t a l hours of bright sunshine of the season as emphasized by White (1938). The regression of the incidence of BR on t o t a l hours of bright sunshine was most s i g n i f i c a n t when the time period was extended to seven weeks before harvest (W0*W2+W4+W6-(W1+W3+W5+W7))» suggesting that the influence of bright sunshine on BR incidence may be cumulative. The maximum and minimum temperatures recorded at the weather stations did not appear to be related with BR incidence, thus giving support to the idea that l i g h t i s the important fa c t o r i n the models discussed .-.-above. 62 In addition to the t o t a l s of hours of bright sunshine, there are three f l u c t u a t i o n or PLUTO values tabulated i n Table 1 2 . The use of the maxima of the "A" values which are differences between consecutive weeks l n terms of fluctuations i n hours of bright sunshine from day to day l n a given week, showed a negative r e l a t i o n s h i p . One of the two examples Is the equation Y=3.82-0 .1291X (Table 1 2 ) , where X Is the maximum of PLUTO values which are A l , A2, A3,tA4, and A5. This equation means that, withlm a period of f i v e weeks before harvest, the maximum value i n d i f f e r -ences between consecutive weeks i n terms of t o t a l d a i l y d i f f e r -ences i n hours of bright sunshine was correlated s i g n i f i c a n t l y with the incidence of BR. The negative c o e f f i c i e n t (-0.1291) indicates that the greater the maximum of FLUTO value, the smaller the Incidence of BR. In other words, an occurrence of a week with r e l a t i v e l y uniform weather, followed or preceded by a week of very variable weather i n terms of hours of bright sunshine, within a period of f i v e weeks, should decrease the incidence of BR. This type of environmental e f f e c t c o n f l i c t s with the known BR incidence i n B r i t i s h Columbia i n 1969. There was very high incidence of BR on Vancouver Island during May 14 - 2 0 , I969 when there was a week with no f l u c t u a t i o n preceded by the week with a considerable f l u c t u a t i o n i n terms of hours of bright sunshine; but there was a very low Incidence of BR on the Lower Mainland during the same period when a l l weeks had f l u c t u a t i n g weather. This contradiction warranted r e j e c t i o n of the equation. The foregoing i s also true f o r the other equation Y=3.86-0 . 1324X: (Table 12) where X i s the maximum of PLUTO values which 63 are A2, A3, A4, and A5t therefore, t h i s model was re jected. A larger d a l l y f l u c t u a t i o n of hours of br ight sunshine during harvesting weeks was associated with a higher Incidence of BR, I f the preceding week had a smaller f l u c t u a t i o n of hours of br ight sunshine as Indicated by the p o s i t i v e c o e f f i c i e n t (0.0809) f o r the combination of W0-W1 f o r FLUTO i n Table 12, which was h ighly s i g n i f i c a n t . This regress ion, Y=l.62+0.0809X was most suited to expla in ing the dif ference of the incidence of BR i n 1969 between the Vancouver Is land and the Lower Mainland commercial houses, when the former had a high incidence of BR i n contrast to the very low incidence on the Mainland. This r e l a t i o n s h i p may be seen i n Figure 3 as a marked decrease i n the hours of br ight sunshine during the week of May 6-11 i n the Lox<rer Mainland record. (That week was Wl f o r the dif ference i n the BR inc idence) . These records suggested that a four day period instead of a seven day period was worth considerat ion, and the several patterns or models are l i s t e d i n Table 15. Again the W0-W1 combination was the only one to show a s i g n i f i c a n t regres-sion of BR on the f l u c t u a t i o n i n the hours of br ight sunshine.. The r 2 f o r that regression was 0.4-2 which i s smaller than, or less s i g n i f i c a n t than the r 2 of 0 .52 f o r the combination of W0-W1 for FLUTO i n Table 6, suggesting that the d a i l y f l u c t u a t i o n accumulated f o r seven days was more revea l ing than accumulating the largest four days of a week i n order to e x p l a i n 1 the Incidence of BR. The examination of the weather data i n general Indicates the f o l l o w i n g two points» 64 A. BR incidence i n B.C. greenhouse tomatoes appears to be associated with the c y c l i c occurrence of a sunny week and a cloudy week. B. The low incidence of BR during May 14-20 i n 1 9 6 9 on the Lower Mainland may be attributed to the marked d a i l y f l u c t u a t i o n of hours of bright sunshine during May 6 - 1 3 . whereas the high BR Incidence on Vancouver Island was associated with v i r t u a l l y no fl u c t u a t i o n . 2) The influence of weekly al t e r n a t i o n of l i g h t and temperature conditions on the incidence of BR. The primary purpose of the growth chamber experiments was to test the hypothesis which was derived from the previous study of the association of hours of bright sunshine and the incidence of BR. The hypothesis proposed that there i s a l i n e a r association between the BR incidence and the combination of t o t a l hours of bright sunshine. The l i n e a r regression proposed was Y=1.51-0.0167X, where Y Is the severity of the Incidence of BR during a given week, and X i s the t o t a l hours of bright sunshine f o r the combination of eight weeks, W0-W1+W2-W3+W4-W5+W6-W?. The regression equation implies three predictions. The f i r s t and the most important prediction i s that the weekly alt e r n a t i o n of l i g h t conditions, sunny-day l i g h t and cloudy-day l i g h t (Fig.2) w i l l produce BR, since Y can be 3 when X= - 8 9.2. S i m i l a r l y , Y can be 0 when X = 9 0 . 4 . This r e l a t i o n s h i p i s seen i n Figure 5« The smaller the X value, the larger the Y value ( i . e . the severity of the incidence of BR).. Figure 6 shows how 65 the l i R h t condition was employed l n TcLc and TaLa treatments. Supposing f r u i t s were harvested during the 9 t h week after the i n i t i a l treatment, as shown in Figure 6, then the crops w i l l be high in the incidence of BR as X (which i s a TOTAL of W0+W2+W4+W6-(W1+W3+W5+W7)) becomes -210 (derived from 52 .5 *+52.5 +52.5+52.5-(105**+105+105+lO5+105)). The X values i n TcLa and TaLa were exaggerated i n the present experiment to ensure that contrast-ing effects of the li g h t treatments. The X value of -210 corres-ponds to a Y value of 3 (any Y value over 3 was regarded as 3 ) . But, i f the harvest was done i n the 1 0 t h week, the X value w i l l become 210 which corresponds to a Y value of 0 (any Y value smaller than 0 was regarded as 0 )« therefore, there w i l l be l i t t l e incidence of BR, Thus the incidence of BR w i l l depend on the week designated as WO i n the use of the model. Therefore, the second prediction i s that the incidence of BR produced by the weekly alternation of light conditions w i l l occur as a weekly cycle. The regression equation i s based on eight weeks of treatment period because X i n the equation i s a combination of lig h t records over eight weeks. Thus the third prediction i s that eight weeks of the treatment period may be needed to produce BR. The f i r s t prediction appeared to be realized because the TcLa treatment, where daily temperature conditions were alternated weekly, produced a signifi c a n t l y greater percentage *i ( 7 . 5 hours/day)x(7 days/week)=52.5 hours/week **i (15 hours/day)x(7 days/week)=105 hours/week Figure 5 The regression equation used for developing the hypothesis. Y: Severity of the incidence of BR. X: TOTAL of W0+W2+W4+W6- (Wlf W3+W5+W7) . > > 4J I-I CO r-l -U a) Pi M W7 W5 ' W3 Wl W6 W4 W2 • • 1 2 3 4 5 6 7 8 9 10 11 12 weeks of treatments Figure 6 Schematic figure of l i g h t treatment in TcLa and TaLa conditions, 67 of BR f r u i t s than. ToLc, where temperature and l i g h t conditions were held consistent. However, the TaLa treatment where the l i g h t conditions were alternated, but temperatures were also alternated, did not give a s i g n i f i c a n t l y higher incidence of BR than the control, TcLc. The e f f e c t of a l t e r n a t i o n of l i g h t conditions seemed to be n u l l i f i e d by the a l t e r n a t i o n of tempera-ture conditions. The second prediction proposes that f r u i t harvested during even weeks w i l l have absence or low Incidence of BR. This prediction i s based on the f a c t that the f i r s t cycle of treatments began with cloudy-day l i g h t . The data i n Table 27 shows no such r e l a t i o n s h i p ! therefore the prediction was not v a l i d i n t h i s case. There Is no doubt that many environmental factors are involved i n the occurrence of BR. I t i s also well known that environmental conditions within a greenhouse d i f f e r from those i n a growth chamber. Thus the plants l n the growth chambers i n the present study and the plants grown i n the commercial greenhouses may have responded d i f f e r e n t l y . Such d i f f e r e n t responses may explain the fact that the incidence of BR was not on a weekly cycle. The period of one week per harvest may have been inappropriate. When considering the t h i r d prediction the data i n Table 16 should be handled with special care. The f i r s t harvest began four weeks a f t e r the plants were put l n the growth chambers. Thus f r u i t s were exposed to greenhouse conditions f o r some weeks p r i o r to being placed i n the chambers. S i m i l a r l y other f r u i t s 68 Table 27 The cyclic occurrence of BR with light conditions alternated weekly. Treatment TcLa TaLa Plant Mean Odd weeks 40.0 23.1 47.4 23.1 36.4 0 8.3 12.5 23.9 a even weeks 43.8 40.9 54.5 17.6 28.6 0 23.1 18.4 28.4 a Means with a common letter are not significantly different. 69 which were harvested later were s t i l l subjected to possible influences of greenhouse conditions. These pre-chambering conditions may have had some influence on the production of BR f r u i t s . The regression equation i s based on eight weeks of exposure to the laternating light conditions, suggesting that the influence of light conditions on the Incidence of BR may be cumulative. Thus i t should be recognized that pre-exposure conditions may be important because some influence may have accumulated before the plants were put into chambers. Thus the light conditions or hours of bright sunshine, to which the plants were exposed during the pre-exposure periods, were examined and are shown i n Figure 7. It can be seen that total hours of bright sunshine during Ap r i l 24-30,, and May 1-7 are very close to the expected values derived from the regression-! equation. Plants were put into chambers on May 8. Thus two such weeks should be considered as a possible part of the treat-ment intended to produce BR. Hence, the length of the time of the treatments as shown i n Table l6; may be extended to Include the pre-exposure two weeks. Thus i n Table 16 the 4th week of treatment might be considered the 6th xveek, and similarly 5th would be considered as 7th weeks. The 6th weeks of treatment length i n Table 16 could, be regarded as 8th weeks and that i s the week when f r u i t s in TcLa and TaLa commenced to be harvested in volume. The weeks of Ap r i l 10-16 and 17-24 had the total hours of bright sunshine very different from the expected values accor-dingly to the regression equation. The influence of these two weeks on the incidence of BR i s unknown. However, one of the 70 T J V 7 V May 1970 75.9 T o t a l hours of b r i g h t sunshine (Expected) (37.8) D i f f e r e n c e (Expected) 47.6 (-22.4) 28.3 (60.2) l V_ r 44.0 (37.8) / \ y -15.7 (22.4). -17.4 (-22.4) 61.4 (60.2) / F i g u r e 7 Hours of b r i g h t sunshine to which the p l a n t s were exposed before being put i n chambers, and corresponding expected hours of b r i g h t sunshine f o r the production of BR f r u i t s . 71 s i g n i f i c a n t regressions l i s t e d i n Table 12 i s based on f i v e weeks of hours of bright sunshine before harvest, implying that only f i v e weeks of treatment may be enough to produce BR, therefore weeks of A p r i l 10-16 and 17-24 may not have been important i n producing BR. F r u i t s harvested during the 4th and 5th week after being put into chambers (Table 16) were exposed to greenhouse conditions, the influence of which on the incidence of BR i s uncertain, f o r two weeks and one week respectively. The number of f r u i t s harvested during those two weeks i s too small to compare with the number of f r u i t s harvested f o r the rest of weeks f o r the e f f e c t of treatment lengths; therefore the t h i r d prediction from the regression equation-could not be tested with the data i n Table 16. Apart from the f i t n e s s of the experimental re s u l t s to the hypothesis, the data.in Table 16 suggested that there Is a compensatory e f f e c t of l i g h t and temperatures i n BR incidence. The higher incidence of BR r e s u l t i n g from the alte r n a t i o n of either l i g h t or temperature conditions, was reduced when l i g h t and temperature conditions were alternated simultaneously (Table 16). In other words the data suggests that the Incidence of BR may be reduced by keeping the greenhouse temperature cool-er during cloudy days, and even warmer on sunny¥days. It i s believed that growers usually control v e n t i l a t i o n i n just the opposite way. 72 Abnormality In the affected tissue i s associated with early l i g n l f i c a t i o n of c e l l walls, which i n turn results i n a decrease l n permeability of c e l l walls, and hence renders the c e l l more vulnerable to injury caused by physiological or mechanical stress (Sadik and Mlnges 1966). The metabolic pathway for l i g n l f i c a t i o n i s summarized by Shubert ( I 9 6 5 ) . These two sources can be used to develop a hypothetical scheme for tissue browning as follows.. polyphenoloxldase., sugars ^ phenolic l i g n i n ce^Ll^T' 11 ssue acids + * formation ^breakdown ~ ^browning r ! I stimuli 1 stress I f r u i t J f r u i t ripening maturation' 1 In this scheme, a certain kind of stimulus or stimuli are needed to i n i t i a t e l i g n l f i c a t i o n and deposit enough Hgnlm in the c e l l wall so that the c e l l becomes vulnerable to Injury which i s a result of stress during f r u i t ripening. That a stress must be applied during f r u i t ripening matches the "shock" reaction theory of TMV infection, which i s shown when a TMV-free plant i s inoculated with the virus when fr u i t s are about to ripen. Lignin formation may start during the period of f r u i t maturation and may continue i n the affected tissue during ripening. When c e l l s are injured and the tissue broken down, phenolic acids may be used to form polyphenols, catalyzed by the polyphenoloxldase, which makes the tissue brown. The high ac t i v i t y of polyphenoloxldase i n the affected areas has 73 been reported (Kidson 1958, Tompkins 1963, Hobson 1967). Then Walker ( I 9 6 2 ) reported that f e r u l i c and caffeic acid were lower i n the affected tissue than i n the normal f r u i t , leads to the deduction that i t i s the rate of conversion of phenolic acids into polyphenols and/or lignln that i s abnormal rather than the synthesis of phenolic acids. A Kind of stimulus by which early l i g n i f i c a t i o n i s i n i t i a t e d and. continues to accumulate may vary with different situations. Environmental factors Influencing l i g n l n formation were reviewed by Brown (1966), but no definite effects of environmental factors i s known. It seems probable, from the present study, that weekly alternation of light and tempera-ture conditions may promote lign i f I c a t i o n . The degree of c e l l wall l i g n i f i c a t i o n could be Increased during Wl - W7 period so that the tissue becomes vulnerable to an injury caused by a stress. Such a stress could result from a high temperature with a low light level during a period of the WO which followed the high temperature with the high light level of the Wl. The higher temperature could allow a higher rate of respiration which demands more photosynthate to be supplied, whereas the low light level w i l l decrease the rate of photo-synthesis. Thus under these conditions there would be a shorts age of the photosynthate. The shortage would be greater when the c e l l wall i s excessively l i g n i f i e d because i t would impede the rate of translocation. Taylor (1957) and E l l s (I96D suggested that the translocation of sugars was impaired i n the affected areas. This local shortage of materials may disturb the normal metabolism, and l n turn may cause a stress. If a low light level was coupled with a lower temperature, the stress 74 may not occur as the respiration rate would also be decreased. A stimulus for lignin- formation may be provided by weekly alternation of light or temperature as indicated i n the present study; but, the actual stimulus i s not known. In the TaLa conditions, the stimulus for lig n l n formation may have been exerted during the period of ¥1 - W7, but the stress does not appear to be as great as i n the case of TcLa and TaLc con-ditions, as indicated by the production of more BB f r u i t s than TcLc but mueh less than TcLa and TaLc conditions (Table 16). In the proposed hypothetical scheme for tissue browning, a stress i s needed to damage the c e l l which had become suscep-ti b l e to an injury because of the excess lignifIcation. I t i s obvious that the more the c e l l i s l i g n i f l e d , the more the c e l l w i l l lose p l a s t i c i t y and w i l l become vulnerable to the injury. Probably, the greater the stress, the less l i g n i -f i cation required to permit injury. This Idea could be applied to the regression equation Y=1.62+0.0809X (Table 14),. where X Is the FLUTO value for the combination of WO - Wl. That equation was used to explain the difference l n the i n c i -dence of BR on Vancouver Island and the Lower Mainland i n 1969,. during the period of May 14 - 20. The equation indicates that the greater the FLUTO value i n WO than i n Wl, the more BR w i l l occur. In other words, when the dally fluctuations in the hours of bright sunshine are greater during the harvest period (WO) after the week (Wl) which had less fluctuations, the incidence of BR w i l l be greater. In the case of the weather pattern of May, 1969 (Fig. 3) on Vancouver Island where the 75 week (WO) with.much d a i l y f l u c t u a t i o n i n the hours of bright sunshine followed the week (Wl) with v i r t u a l l y no f l u c t u a t i o n , the stress which was produced by t h i s f l u c t u a t i o n may have been much greater than the case f o r the Lower Mainland where both WO and Wl had much the same f l u c t u a t i o n as shown by the X value (FLUTO f o r WO-Wl) of - . 1 0 i n Table 14. Jones and Alexander (1962) reported the e f f e c t of changing temperature conditions during plant development. They increased the incidence of BR i n the greenhouse from 20.0 to 32.1^ or 10.9 to 25.1$ on plants with low l e v e l s of potassium by subjecting plants to room temperature (65-70 F/58-6O F, day/night) f o r f i v e days, and then to low temperatures ('55 F/ 50 F,. day/night) f o r two months followed by high temperature (80 F, day and night) f o r the remainder of the season. Thus the temperature conditions were changed three times i n the study beginning at the early stage of plant growth. Gloss (1958) reported that low l i g h t i n t e n s i t i e s one or two weeks pr i o r to ripening resulted i n BR. Agalni the change i n l i g h t conditions was not a long term cycle as l n the present study. However, i t i s i n t e r e s t i n g to note that Just a few changes i n temperature or l i g h t conditions are reported to Influence the incidence of BR whereas the present study indicated that more frequent changes could be needed to produce BR. There are no reports on the e f f e c t of c y c l i c changes i n temperature or l i g h t conditions on the occurrence of BR. Thus further work i s needed to decide how much and how often those conditions should be changed i n order to produce or eliminate BR. 76 3 ) ; Association of BR of greenhouse tomatoes and tobacco mosaic virus (TMV) i n B r i t i s h Columbia i n 1 9 6 9 -Since Boyle and Wharton ( 1 9 5 6 ) reported the shock r e -action of tomatoes to TMV, the role of the virus i n the incidence of IB'seems to be well established. BR of greenhouse tomatoes i n B r i t i s h Columbia i s characterized by presence of necrotic tissue such as that described f o r IB; The obvious question arose: i s BR i n B.C. a r e s u l t of TMV infection? The TMV survey revealed the role of TMV i n BR of B.C. greenhouse tomatoes. As seen In Table 2 1 , not a l l the BR f r u i t s were infected with TMV. Furthermore the prevalence of TMV i n BR f r u i t s and non-BR f r u i t s did not d i f f e r s i g n i f i c a n t l y ! therefore i t does not appear that the TMV" i s the only factor causing BR i n the B;.C. crop. The extreme example i s seen i n the case of grower NO.3 (Table 21) where the crop was apparently free from TMV at the time of sampling and yet BR was present. When a f r u i t and a leaf from the same plant were assayed f o r the virus on Ni glutlnosa i t was noted i n a few cases that either the f r u i t or the leaf from the same plant, but not both, showed TMV symptoms i n the assay. This phenomenon may be explained by Bawden's ( 1 9 6 4 ) review of virus behaviour i n plant diseases, and can be summarized as follows. The movement of virus over a r e l a t i v e l y long distance within a plant may lar g e l y be determined by the d i r e c t i o n i n which the main food stream i s moving. Developing f r u i t trusses of tomatoes often became infected at the same time as roots and young leaves, whereas mature leaves adjacent to trusses remained freevfrom virus f o r weeks. It takes less time f o r virus to i n f e c t a l l parts of 77 young plants than l n the case of old plants. A l l the leaves of small tomato plants became Infected soon a f t e r the youngest ones, but three weeks were needed f o r plants i n the f r u i t i n g stage. In large plants, i n f e c t i o n of mature leaves was usually r e s t r i c t e d to limited areas around the main veins even three months a f t e r the i n i t i a l inoculation. A very noticeable case was that of grower NO.8 where 26 f r u i t s out of 33 TMV-infected f r u i t s did not show TMV i n the corresponding leaf samples. Those facts suggest that the Infection of those plants with TMV occurred at a r e l a t i v e l y late stage of plant development, which indicated that BR symp-toms i n that greenhouse could, be a r e s u l t of the "shock reaction" a f t e r the i n f e c t i o n of TMV. The case of growers NO. 5 and NO.6 leads to the same speculations. The presence of TMV. i n a l l the samples both i n f r u i t s and leaves suggests that i n f e c t i o n occurred at an early stage. If t h i s were sc then plants were well beyond the "shock reaction" stage at the time of f r u i t ripening and hence should be free of virus-induced IB. This may be further evidence that the role of TMV i s not the Important factor i n causing BR i n t h i s region. Table 23 shows that a f r u i t Is a more r e l i a b l e source f o r virus assay than a mature lea f , suggesting that f r u i t s should always be used f o r the virus assay i f one;*s intere s t i s l n TMV i n f r u i t s . k), Association of BR and potato virus X (PVX), 78 Some tomato plants grown by Koskitalo l n the Department of Plant Science at the University of B r i t i s h Columbia produced severe BR symptoms i n the controlled growth chambers. The plants were obviously Infected with a virus desease,,and It was noted t h i t the i n f e c t i o n had occurred i n the early growth stage of plants. Also, plants free from virus were free from BR. These plants were included i n the TMV studies previously described. The TMV assay gave negative r e s u l t s ; therefore a further assay using Gomphrena  globosa was employed and the virus was i d e n t i f i e d as potato virus X, hereafter designated as PVX. The e f f e c t of t h i s PVX on the BR incidence was further studied. The r e s u l t s of the experiment as. shown i n Table 24 f a i l e d to confirm Koskitalo's observation. Admittedly,, the only BR i n the experiment occurred on one plant infected by PVX. This BR incidence could be e i t h e r by chance only or by the PVX i n f e c t i o n . The discrepancy between Koskitalo's r e s u l t s and those reported here may be due to d i f f e r e n t growing conditions. The plants grown by Koskitalo and those f o r the experiment reported here, were kept i n the greenhouse u n t i l some f r u i t s reached maturity. Thus these plants were grown during d i f f e r -ent times of the year as well as i n d i f f e r e n t years. The d i f f e r e n t pre-chamber conditions may account f o r the d i f f e r e n t incidence of BR i n spite of the s i m i l a r procedure i n the same greenhouses and growth chambers. The growing conditions f o r 79 the control plants l n the PVX experiment may be such that BR did not develop. A l l the plants which remained i n the greenhouse, whether infected or not with PVX, had no BR. These apparently favourable growing conditions i n the green-house may have been sufficient to counteract the adverse effect of PVX, i f there i s any. It i s known that PVX usually causes only mild mosaic symptoms on tomato plants. However, a very severe necrotic disease, known as "streak" w i l l occur, If tomato plants are infected with both PVX and TMV' (Bawden 1964). In B.C. green-houses, ln spite of the wide spread occurrence of TMV, streak disease i s very rare, suggesting that PVX i s not a problem for commercial growers. The non-significant difference between f r u i t weight of PVX infected plants and control plants may be a mani-festation of the mild effext which PVX i s reported to have on host tomato plants. The higher average f r u i t weights and total yields per plant are no doubt a result of the difference in the greater amount of radiant energy available i n the green-house compared to the lower light intensity of the growth chambers. SUMMARY AND CONCLUSION! 80 In a study which was concerned with BR i n the greenhouse tomato i n B r i t i s h Columbia, the possible factors which i n f l u -ence the incidence of t h i s disorder were sought i n the hours of bright sunshine and i n the viruses. By f i n d i n g some s i g n i -f i c a n t l i n e a r regressions of the incidence of BR on the combi-nations of hours of bright sunshine, a pattern of hours of bright sunshine was postulated to produce BR, and t h i s pattern was sub-sequently tested i n the growth chambers. Two level s of maximum temperature and two levels of the duration of high l i g h t conditions were employed, i n a f a c t o r i a l combination, to make four treatments f o r the experiment im the growth chambers. Conclusions from these studies were as follows: 1) . The incidence of BR l n the B.C. greenhouse tomatoes appeared to be associated with the c y c l i c occurrence of sunny weeks and cloudy weeks. 2) . When the temperature conditions were held consistent the weekly a l t e r n a t i o n of l i g h t conditions could produce a s i g n i f i c a n t l y greater percentage of BR fruits/thanrs i n the con-t r o l treatment, i n which the l i g h t and temperature conditions were kept consistent. However, t h i s effect of weekly a l t e r -nation of l i g h t conditions was n u l l i f i e d by the simultaneous alter n a t i o n of temperature conditions, suggesting some compen-satory e f f e c t of temperature and l i g h t conditions. 3). The role of TMV. on the Incidence of BR i n the B.C. greenhouse tomatoes did not appear to be the important factor 81 In the spring crops i n 1969. 4) . The effect of PVX on the incidence of BR was not clear. 82 LITERATURE CITED Bawden, F.C. 1964. 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A report of gray-wall or in t e r n a l browning of tomato i n South F l o r i d a . Plant Dis. Reptr. 34« 3 7 9 - 3 8 0 . Taylor, G.A. 1957* The influence of some environmental and n u t r i t i o n a l factors on the incidence of internal-browning of tomato. Diss. Abstr. 1 7 » 2 1 1 - 2 1 2 . Tompkins, D.R. 1 9 6 3 . Factors related to Internal browning of tomato f r u i t s (Lyooperslcon esculentumr M i l l . ) . Ph.D. Thesis. Univ.of Maryland. Walker, J.R.L. 1 9 6 2 , Phenolic acid i n "cloud" and normal tomato f r u i t wall tissue. J.Sci.Fd.Agri. 131 3 6 3 - 3 6 7 . White, H.L. 1 9 3 8 . Further observations of the incidence of blotchy ripening of the tomato. Ann.Appl.Biol.. 25* 5 4 4 - 5 5 7 . Winsor, G.W., Davies, J.N. and Massey, D.M. 1 9 6 2 a . Composition of tomato f r u i t . I I I . Juices from whole f r u i t and locules at d i f f e r e n t stages of ripeness. J.Sci.Fd.Agri. 1 3 ' 108-115. • 1 9 6 2 b . Composition of tomato f r u i t . IV. Changes i n some constituents of the f r u i t walls during ripening. J.Sci.Fd.Agri. 1 3 ' 141-145. , 1 9 6 2 c . Composition of tomato f r u i t . V. Compari-son of the d i f f e r e n t l y colored areas of the walls of "Blotchy" tomatoes. J.Sci.Fd.Agri. 13« 145-147. Winsor, G.W. and Long, M.I.E. I967. The e f f e c t of nitrogen, phosphorous, potassium, magnesium and lime i n f a c t o r i a l combination on ripening disorders of glasshouse tomatoes. Winsor, G.W. and Massey, D.M. 1 9 5 8 . The comparison of tomato f r u i t . I. The expressed sap of normal and "blotchy" tomatoes. J.Sci.Fd.Agri. 9» 4 9 3 - 4 9 8 . . 1 9 5 9 . The composition of tomato f r u i t . I I . Sap expressed from f r u i t showing c o l o r l e s s areas i n the walls. J.Sci.Fd.Agri. 1 0 ' 3 0 4 - 3 0 7 . 87 Winsor, G.W., Messing, J.H.L, and Long M.I.E. 1965a. The e f f e c t s of magnesium deficiency on the y i e l d and quality of glasshouse tomatoes grown at two l e v e l s of potassium. J.Hort.Scl. 4 0 r 118-132. Winsor, G.W., Messing, J.H.L., Hobson, G.E. and Long, M.I.E. 1965b. The magnesium content and potassium magnesium r a t i o of tomato leaves i n r e l a t i o n to degree of c h l o r o s i s . J.Hort.Scl. 4 0 » I 5 6 - I 6 6 . Woods, M.J. 1963a. Color disorders of ripening tomatoes. 1. Introduction and l i t e r a t u r e review. I r i s h J . A g r i . Res. 2 i 195-206. . 1963b. Color disorders of ripening tomatoes. 2. F r u i t color i n r e l a t i o n to shade, s o i l moisture tension and d e f o l i a t i o n . I r i s h J.Agri.Res. 2i 207-216. Woods, M.J. 1964a. Color disorders of ripening tomatoes 4 . F r u i t color i n r e l a t i o n to variety and nitrogen n u t r i t i o n . I r i s h J.Agri.Res. 3» 29-36. 1964b. Color disorders of ripening tomatoes 5. F r u i t color l n r e l a t i o n to i r r i g a t i o n and n u t r i t i o n . I r i s h J.Agri.Res. 3« 141 - 1 5 0 . . 1965. Color disorders of ripening tomatoes Z. Occurrence l n early tomato crops. I r i s h J.Agri. Res. 4 : 25-35. . I 9 6 6 . The e f f e c t s of some n u t r i t i o n a l and environ-mental factors on f r u i t quality i n tomatoes. Symposiunr 1966. pp.313-323. APPENDIX The values of TOTAL and FLUTO f o r the combinatior selected weeks l i s t e d i n Table 1. Week TOTAL or FLUTO 1 2 3 4 TOTAL 13.7 9.2 25.5 4.6 FLUTO 10.3 3.8 7.0 14.5 TOTAL 16.3 20.9 27.5 8.0 FLUTO 10.9 1.0 1.6 11.1 A l A2 A3 TOTAL 8,8 7.9 0.7 3.3 FLUTO 1,5 10,9 7,0 16.9 A4 TOTAL 10.8 25. 7 6.2 36.4 FLUTO 1.3 20.9 6.5 15.4 A5 TOTAL 20.9 16.6 11.7 24.1 FLUTO 1.3 0.6 2.6 4.3 A6 TOTAL 8.4 11.5 28. 5 39.8 FLUTO 3.1 12.0 6. 6 9.5 A7 TOTAL 21.5 2.3 27.6 35.8 FLUTO 24.7 2.7 9.9 26.4 For A l , A2,A3, A4, A5, A6 and A7, see Table 9. of two weeks f o r 12 cases of 12 5 6 20. 6 5. 7 4.7 15.2 1.0 37.5 19,2 14.3 0,8 17.9 15.2 2.5 20.7 17.4 4.5 4.5 8.8 31.8 1.4 12.7 13.9 19.7 6.8 24.7 2.3 7.9 3.0 1.4 0 3 cases 7 8 47.2 9.6 14.8 0.1 7.0 34.5 2.2 5.6 9.5 13.2 4.8 7.6 22.3 24.9 9.9 11.0 26.8 36.2 23.1 20.1 26. 5 21.4 1.4 27.5 2.9 10.4 26.1 0.9 1 1 9 10 10.6 7.1 3.3 10.8 20.6 30.0 4.7 0.2 1.0 19.2 19.2 14.6 0.8 17.9 15.2 8.1 20.7 4.5 4.5 15.0 8.8 47.2 1.4 14.8 13.9 7.0 6.8 7.6 1 1 11 12 32.7 53.0 0.3 5.2 7.1 2.5 10.8 7.2 30.0 2.0 0.2 0.1 19.2 62.1 14.6 10.9 17.9 15.2 8.1 0.4 4.5 4.2 15.6 9.2 47.2 17.7 14.8 0.4 1 3 CD CD 

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