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UBC Theses and Dissertations

Effect of captan on pollen germination and fruit set in strawberry Chen, Liang-ing 1968

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EFFECT OF CAPTAN ON POLLEN GERMINATION AND FRUIT SET IN STRAWBERRY by LIANG-ING CHEN B.Sc. Taiwan P r o v i n c i a l Chung-Hsing University, Taiwan, Republic of China, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IK^AES! CULTURE i n the D i v i s i o n of Plant Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1968 ABSTRACT Using strawberry as a test plant, captan has been shown to i n h i b i t p o l l e n germination when included i n or sprayed on the germination medium, or when sprayed on anthers a f t e r pollen dehiscence. Toxic e f f e c t s did not disappear during prolonged germination. However, pollen germination was s l i g h t l y affected by captan sprayed on the undehisced anthers. When open flowers were sprayed before anther dehiscence, berry set was reduced i n the v a r i e t y S i l e t z but not i n the v a r i e t y Northwest. When sprayed a f t e r anther dehiscence, achene set, and berry development were decreased. The proportion of mishappen f r u i t s increased with captan concentration. P o l l i n a t i o n from sprayed anthers was not as ef f e c t i v e i n f r u i t s e t t i n g as control p o l l i n a t i o n of sprayed p i s t i l s . Sprays applied to p i s t i l s either just before or just a f t e r p o l l i n a t i o n decreased f r u i t set. F r u i t set was not affected by sprays one day aft e r p o l l i n a t i o n . Captan therefore seemed to act d i r e c t l y upon pollen germination and not upon the r e c e p t i v i t y of the stigma or upon pol l e n tube growth i n the sty l e or upon f e r t i l i z a t i o n . In presenting this thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y 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 a v a i l a b l e for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by h i s representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. D i v i s i o n of Plant Science The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, B.C. Canada December, 1968. ACKNOWLEDGMENTS I wish to thank Dr. G. W. Eaton, Associate Professor, D i v i s i o n of Plant Science, U n i v e r s i t y of B r i t i s h Columbia, for his guidance and supervision during planning, experimental phases and f i n a l reporting of this thesis, as well as his continuous encouragement. Acknowledgment i s also extended to the other members of my thesis committee: Dr. V. C. Brink, D i v i s i o n of Plant Science Dr. A. J . Renney, D i v i s i o n of Plant Science Dr. C. A. Hornby, D i v i s i o n of Plant Science Dr. D. P. Ormrod, D i v i s i o n of Plant Science The Canada Department of A g r i c u l t u r e , Research Station, Agassiz, B.C. provided the i n i t i a l strawberry plants used i n t h i s project. My sp e c i a l thanks to D. Armstrong and A. Battensby for t h e i r help i n growing strawberry plants i n the f i e l d . The research was supported i n part by National Research Council operating grant A2023 awarded to Dr. G. W. Eaton. - i v -TABLE OF CONTENTS Page I. INTRODUCTION 1 II . LITERATURE REVIEW 2 A. E f f e c t of fungicides on pol l e n germination and f r u i t set 2 B. Seed count i n strawberry 6 C. The control of strawberry f r u i t r o t 7 I I I . MATERIALS AND METHODS 9 Seed count study 9 S t a t i s t i c a l analyses 10 A. Polle n germination tests 10 1. Polle n germination with captan i n the media . . . . 10 2. P o l l e n germination with captan on the media . . . . 11 3. P o l l e n germination with captan sprayed on undehisced anthers 11 4. Po l l e n germination with captan sprayed on dehisced anthers 12 B. Greenhouse experiments . . . 13 1. Berry set with captan sprayed on flowers before anther dehiscence 13 2. Berry set with captan sprayed on flowers a f t e r anther dehiscence 13 3. Comparison of spraying p i s t i l s versus anthers . . . 13 4. Berry set i n p i s t i l s sprayed at i n t e r v a l s a f t e r p o l l i n a t i o n 14 5. Berry set i n p i s t i l s p o l l i n a t e d at i n t e r v a l s a f t e r spraying 14 IV. RESULTS 15 - V -Page Seed count study 15 A. Po l l e n germination 15 1. Po l l e n germination with captan i n the media . . . 15 2. Pollen germination with captan on the media . . . 15 3. Po l l e n germination with captan sprayed on undehisced anthers . 18 4. Po l l e n germination with captan sprayed on dehisced anthers 20 B. Greenhouse experiments 22 1. Berry set with captan sprayed before anther dehiscence 22 2. Berry set with captan sprayed a f t e r anther dehiscence . 24 3. Comparison of spraying p i s t i l s versus anthers . . 26 4. Berry set i n p i s t i l s sprayed at i n t e r v a l s a f t e r p o l l i n a t i o n . . . . . 28 5. Berry set i n p i s t i l s p o l l i n a t e d at i n t e r v a l s a f t e r spraying . . . . . . . . . . . . . . 30 V. DISCUSSION 33 A. Pollen germination tests . 33 1. Po l l e n germination with captan i n the media . . . 33 2. Po l l e n germination with captan on the media . . . 33 3. Po l l e n germination with captan sprayed on undehisced anthers 34 4. P o l l e n germination with captan sprayed on dehisced anthers 34 B. Greenhouse experiments 35 Days required to ripen . 35 Berry weight and number of achenes 35 - v i -Page 1. Berry set with captan sprayed before anther dehiscence 35 2. Berry set with captan sprayed a f t e r anther dehiscence . . . . . 36 3. Berry set with captan sprayed on p i s t i l s or anthers 36 4. Berry set i n p i s t i l s sprayed at i n t e r v a l s a f t e r p o l l i n a t i o n 37 5. Berry set i n p i s t i l s p o l l i n a t e d at i n t e r v a l s a f t e r spraying 37 VI. REFERENCES 39 VTI. APPENDIS 43 - v i i LIST OF TABLES Page Table 1. P o l l e n germination as affected by captan sprayed on the media 17 Table 2. P o l l e n germination as a f f e c t e d by captan sprayed on undehisced anthers 19 Table 3. P o l l e n germination as af f e c t e d by captan sprayed on dehisced anthers . . . 21 Table 4. Berry set as af f e c t e d by captan sprays before anther dehiscence . 23 Table 5. Berry set as af f e c t e d by captan sprays a f t e r anther dehiscence . . . . . . . . 25 Table 6. The e f f e c t upon berry set of spraying p i s t i l s or anthers with captan . . . . . . . 27 Table 7. Berry set with captan sprays at i n t e r v a l s a f t e r p o l l i n a t i o n 29 Table 8. E f f e c t s upon berry set of p o l l i n a t i o n at i n t e r v a l s a f t e r spraying 31 Table 9. The reaction of captan sprayed p i s t i l s to p o l l i n a t i o n at i n t e r v a l s a f t e r spraying . . . 32 Table 10. F - p r o b a b i l i t i e s from the analysis of variance for p o l l e n germination as af f e c t e d by captan sprayed on the media 44 Table 11. F - p r o b a b i l i t i e s from the analysis of variance for p o l l e n germination as af f e c t e d by captan sprayed on undehisced anthers . . . . . . . . 45 Table 12. F - p r o b a b i l i t i e s from the analysis of variance for p o l l e n germination as af f e c t e d by captan sprayed on dehisced anthers 46 Table 13. F - p r o b a b i l i t i e s from the analysis of variance for berry set as a f f e c t e d by captan sprays before anther dehiscence 47 Table 14. F - p r o b a b i l i t i e s from the analysis of variance for berry set as af f e c t e d by captan sprays a f t e r anther dehiscence 48 - v i i i Page Table 15. F-probabilities from the analysis of variance for berry set spraying either pistils or anthers . 49 Table 16. F-probabilities from the analysis of variance for berry set when pistils were sprayed at intervals after pollination 50 Table 17. F-probabilities from the analysis of variance for berry set in pistils pollinated at intervals after anthesis . 51 INTRODUCTION V a r i o u s f u n g i c i d e s p r a y s a r e recommended f o r c o n t r o l l i n g common t r e e -f r u i t d i s e a s e s u s i n g a t l e a s t 3 o r 4 a p p l i c a t i o n s d u r i n g b l o s s o m . L i t t l e i n f o r m a t i o n i s a v a i l a b l e c o n c e r n i n g the e f f e c t s o f t h e s e s p r a y s on the p h y s i o l o g y o f p o l l e n g e r m i n a t i o n and f r u i t i n g . S e v e r a l w o r k e r s have i n d i c a t e d t h a t low t o l e r a n c e s o f t r e e - f r u i t p o l l e n g r a i n s to f u n g i c i d e s o r o t h e r p e s t i c i d e s can r e s u l t i n r e d u c e d p o l l e n g e r m i n a t i o n i n l a b o r a t o r y t e s t s when a p p l i e d i n v i t r o o r i n the o r c h a r d d u r i n g bloom. There a r e c o n t r a d i c t o r y r e p o r t s however c o n c e r n i n g the i m p o r t a n c e o f t h e s e e f f e c t s i n r e l a t i o n to f r u i t - s e t t i n g . The p r e s e n t greenhouse s t u d i e s w i t h s t r a w b e r r y f l o w e r s were d e s i g n e d t o t e s t whether the f u n g i c i d e c a p t a n ( N - ( t r i c h l o r o m e t h y l m e r c a p t o ) - 4 - c y c l o h e x e n e -1,2-dicarboximide) w i l l i n h i b i t s t r a w b e r r y p o l l e n g e r m i n a t i o n and whether t h i s m i g h t a f f e c t t h e development o f achenes and r e l a t e d r e c e p t a c l e t i s s u e . C a ptan i s commonly used d u r i n g bloom t o c o n t r o l a p p l e scab and brown r o t o f s t o n e f r u i t s as w e l l as g r e y mold o f r a s p b e r r y and s t r a w b e r r y . T h e r e f o r e , a l t h o u g h the s t r a w b e r r y i n a c o n v e n i e n t t e s t p l a n t , the r e s u l t s may have w i d e r i m p l i c a t i o n s . - 2 -LITERATURE REVIEW A. E f f e c t of fungicides on pollen,germination and f r u i t set Studies on the e f f e c t of fungicides applied to the open blossoms on f r u i t set date from the use of Bordeaux and sulphur fungicides for con-t r o l l i n g apple scab. MacDaniels and Furr (16) found i n 1930 that sulphur dust lodging on the stigmas of apple blossoms could prevent pollen germ-in a t i o n and reduce or prevent f r u i t set. They stated that the p r a c t i c a l e f f e c t of dusting blossoms may or may not be a reduction of f r u i t set, depending on the time of dust a p p l i c a t i o n with reference to p o l l i n a t i o n , weather conditions and the number of f r u i t s per spur. MacDaniels and B u r r e l l (17) indicated that the greatest reduction i n f r u i t set was caused by a p p l i c a t i o n s of sulphur dust and lime-sulphur spray 24 hours before p o l l i n a t i o n and the next greatest by applications of these fungicides coincident with p o l l i n a t i o n . A further e f f e c t of several copper containing bactericides was found by MacDaniels and Hildebrand (18). They found that a l l treatments reduced the percentage of pol l e n germination and the length of the pollen tube when the b a c t e r i c i d e s were applied to the surface of sucrose-agar media by using a small duster or an atomizer, but did not ser i o u s l y cut down f r u i t set when applied to the blooming trees. They came to the conclusion that the p o l l e n grains might lodge i n between the p a p i l l a e of the stigma and were not i n contact with dust p a r t i c l e s or wet by sprays. MacDaniels and Hildebrand (19) found that a p p l i c a t i o n of copper compounds to the stigmas of apple blossoms had not given the expected r e s u l t s i n reducing the f r u i t set. They indicated that i t was probably r e l a t e d to the lo c a t i o n of the - 3 -p o l l e n grains upon the p a p i l l a e of the stigma with r e l a t i o n to the grains of copper lime dust and the f a i l u r e of the spray to completely cover the stigmatic surface. They suggested that a microscopic study of the germination of pollen upon the treated stigma would give further information and emphasized the very complex nature of the f r u i t s e t t i n g process and the many factors involved. MacDaniels and Hildebrand ( 2 0 ) performed microscopic studies of the germination of p o l l e n upon the treated stigmas. They found that Bordeaux mixture 2 - 6 - 1 0 0 , copper lime 2 0 - 8 0 , and "Mike" sulphur reduced but did not prevent growth of p o l l e n upon the stigma, but E l g e t o l a t 0.257o completely prevented pollen germination on stigmas. F i e l d t r i a l s indicated that E l g e t o l i n h i b i t e d f r u i t set s e r i o u s l y on apple trees and t h i s material has since been used extensively i n f r u i t thinning. . Watson ( 3 1 ) designed an experiment to study the s p e c i f i c e f f e c t of E l g e t o l sprays on the structure of the p i s t i l and upon subsequent p o l l e n tube growth. He found no r e l a t i o n between number and length of p o l l e n tubes i n p i s t i l s from treated and untreated flowers, but the y i e l d of f r u i t was reduced s e r i o u s l y when E l g e t o l was sprayed during blossom. He concluded that E l g e t o l destroyed the receptive nature of the stigma, caused dehydration, browning, and death of c e l l s of the p a p i l l a e . This i s now considered to be the main mode by which E l g e t o l acts as a chemical f r u i t thinner. Schmidt (27) performed experiments i n which he detected that c e r t a i n fungicides, e s p e c i a l l y thiuram and captan caused a reduction i n the germin-a t i o n of apple, pear and plum po l l e n when sprayed into the open, blossom. He found no reduction i n y i e l d i n any treatment. Rich ( 2 6 ) found that apple p o l l e n would not germinate i n sucrose s o l u t i o n containing the fungicides: captan, glyodin, dichlone or ferbam while - 4 -sulphur had a s l i g h t depressing e f f e c t . However, these fungicides had no serious e f f e c t on f r u i t set either when sprayed pollen was applied to unsprayed blossoms or unsprayed pollen was applied to sprayed blossoms. The r e c i p r o c a l experiment employed d i f f e r e n t v a r i e t i e s . He concluded that the method of immersing or suspending p o l l e n grains i n fungicide-sucrose sol u t i o n was too severe to determine the safety of using fungicides at blossoming. Eaton (8) also reported that captan sprays applied to apple anthers s i g n i f i c a n t l y reduced p o l l e n germination and i n h i b i t e d pollen tube elongation on sucrose-agar media, although not equally for a l l v a r i e t i e s . Braun e_t al_ (2) studied the e f f e c t of several plant protection materials upon the germination of apple and pear p o l l e n and found that pollen germination was i n h i b i t e d by those plant protection materials which were contained i n the sugar sol u t i o n . Braun et_ al_ (3) sprayed some apple v a r i e t i e s before and during flowering with the following chemicals: Orthocide 83 (0.15% captan), Pomarsol f o r t e (0.15%), A c r i c i d (0.2%), Karathane (0.1%), Morestan (0.03%), Fuklasin u l t r a (0.1%,) and Delan wettable powder (0.1%>) . He showed that spraying during flowering did not increase f r u i t drop. The germination capacity of the pol l e n was unaffected by preblossom spraying, but was often severely i n h i b i t e d by spraying during flowering. No female flower parts were damaged. In a greenhouse t r i a l the flowers were a r t i f i c i a l l y p o l l i n a t e d with sprayed p o l l e n and f r u i t set was greatly reduced. Dhuria et a l (6) investigated the influence of the i n s e c t i c i d e thiodan on p o l l e n germination and f r u i t set i n apple. They found a s i g n i f i c a n t reduction with the a p p l i c a t i o n of 0.2%, thiodan to the germination medium. - 5 -P o l l e n germination and p o l l e n tube growth were also reduced when newly open pollen sacs were thoroughly wetted with an emulsion or suspension of thiodan. Wetting the closed anthers had no e f f e c t . The a p p l i c a t i o n of thiodan to open flowers caused only a s l i g h t reduction i n pollen germination and the percentage of f r u i t set was not affected. The treatment of open anthers or stigmas did not s i g n i f i c a n t l y reduce p o l l e n tube growth. Kaspers ( 1 2 ) reported that sprays of 0.27o Orthocide 50 (captan) applied 3 or 4 times during blossoming to apple trees did not reduce f r u i t set. Other species of t r e e - f r u i t were also examined by several i n v e s t i -gators. Remy (25) worked with peach and plum pollen and found that nearly a l l of the test materials i n h i b i t e d p o l l e n germination more or less severely. Eaton (7) working with sweet cherry p o l l e n grains i n v i t r o used a spraying technique instead of immersion of pollen grains i n the dosage. He found that .sulphur did not reduce pollen germination but dichlone and ferbam reduced germination s l i g h t l y . Captan almost e n t i r e l y prevented pollen germination and arrested the elongation of p o l l e n tubes. C r i s t o f e r i e_t a l ( 4 ) indicated that apricot p o l l e n v i a b i l i t y and f r u i t set were adversely affected by 0.27o ziram (807o a.i.) and p a r t i c u l a r l y by 0.157= TMTD. Similar i n j u r i o u s e f f e c t s on pears were recorded for the ziram spray and for 0 . 1 % dodine ( 6 5 % a.i.) but 0.2% zineb ( 8 0 % a.i.) was harmless. In apple, zineb and dodine reduced pollen v i a b i l i t y and f r u i t set, but ziram was not injuri o u s unless applied at f u l l anthesis i n the laboratory and with c o n t r o l l e d p o l l i n a t i o n i n the f i e l d . There were no s i g n i f i c a n t y i e l d differences between treated and untreated trees of a l l 3 species under natural p o l l i n a t i o n . - 6 -Gartel ( 1 0 ) reported that germination of grape p o l l e n was i n h i b i t e d when several plant protectants were applied over the germination media. Shawa e_t a l ( 2 8 ) reported that captan, ferbam, maneb and phaltan applied to the surface of agar plates consisting of 5% corn meal, 0.27„ dextrose and 0.57= agar'completely i n h i b i t e d cranberry pollen germination. P o l l e n c o l l e c t e d from the sprayed flowers germinated from 40.87o-97.07 o on untreated sugar-agar media, while that from untreated flowers germinated 1007o. He also c a r r i e d out f i e l d t r i a l s with fungicide sprays during the blossoming period and cranberry y i e l d was s i g n i f i c a n t l y reduced. Lockhart ( 1 5 ) has shown that lowbush blueberry pollen had l i t t l e or no germination on a r t i f i c i a l media (5? D agar and 13.57o sucrose) which con-tained ziram or ferbam. Moderate germination occured on media that contained zineb. Poll e n grains from dusted plants germinated as well as the c o n t r o l . Lockhart concluded that the pollen grains were enclosed i n the anthers at time of dusting, and the dust probably did not come i n contact with the pol l e n . He also found that the seed count from fungicide t r i a l plots showed that the number of seeds i n plots treated with fungicides 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 that i n control p l o t s . B. Seed count i n strawberry Seed counts have been used by many investigators to indicate the berry development of strawberry. Nitsch ( 2 2 ) demonstrated that the growth of the receptacle was e n t i r e l y dependent upon the presence of f e r t i l i z e d achenes and obtained evidence that t h i s was mediated through a mechanism invol v i n g auxin-like growth substances. Tukey ( 2 9 ) also observed that there was a d i r e c t r e l a t i o n s h i p between the number of achenes present on the f r u i t and the size of that f r u i t at maturity. The largest f r u i t s at maturity possessed the la r g e s t number of functional achenes, while smaller f r u i t s had a progressively smaller number of achenes. He indicated that a small number of achenes may stimulate p r o p o r t i o n a l l y more development of the receptacle i n milligrams per achene than would a large number. Moore (21) indicated that the seed number and berry weight i n the strawberry were not so c l o s e l y associated as i n the blueberry under con-d i t i o n s of poor f e r t i l i z a t i o n . In the strawberry, each seed either con-tributes more hormone for receptacle growth or the hormone i s u t i l i z e d more e f f i c i e n t l y than under conditions of r e l a t i v e l y f u l l seed set. In either case each seed i s responsible for a greater amount of actual f r u i t weight when seed set i s low. C. The control of strawberry f r u i t rot Grey mold of strawberries caused by B o t r y t i s cinerea (Pers.) Fr. i s the most important f r u i t r o t of strawberries i n many growing areas. In P a c i f i c coast f i e l d s , as elsewhere, losses are most serious when r a i n f a l l i s excessive during the harvest period (23). In the current control program, i t i s recommended that strawberries should be sprayed or dusted with captan at l e a s t 3 times, s t a r t i n g when the f i r s t blossoms emerge (29, 22). Freeman (9) working with the S i l e t z strawberry v a r i e t y found that the fungicides f o l p e t , captan, and thiram proved the most e f f e c t i v e materials for c o n t r o l l i n g grey mold. F r u i t size was a f f e c t e d by treatments, the trend being for f r u i t to be larger from plots treated with the more e f f i c i e n t fungicides. Powell (24) also noted that strawberry plants had benefited n u t r i t i o n a l l y from captan and that f r u i t size was increased. - 8 -Gourley (11) indicated that the b e n e f i c i a l e f f e c t of disease control by a fungicide must be greater than any reduction i n y i e l d due to ph t o t o x i c i t y . There are no reports of e f f e c t s of captan on strawberry p o l l e n germination or f r u i t set. In other crops although captan may reduce p o l l e n germination there may or may not be e f f e c t s on f r u i t set. Reasons for this are not c l e a r . Further research may help explain the apparent contradic-tions among the studies summarized here. - 9 -MATERIALS AND METHODS Two commercial v a r i e t i e s , S i l e t z and Northwest, were used i n the experiments. Stock plants were grown i n the f i e l d i n J u l y to propagate the runner plants. Digging of plants started i n the middle of November and uniform runner plants were brought into a. heated greenhouse. The plants were set into 18-cm pots and the v a r i e t i e s were separately put on two benches under supplementary i l l u m i n a t i o n providing 16-hour d a i l y photoperiods. A f t e r 25 days, the flowers started opening. A l l flowers were marked with a dated tag on the day that they opened, treated i n accordance with the experiment being done and l e f t u n t i l the f r u i t started to turn pink. F r u i t s were harvested when two thirds of the berry surface areas had turned red. Days required to ripen, berry weight, number of sound achenes, number of abortive achenes, number of t o t a l achenes, percentage of sound achenes per berry and berry weight per sound achene were recorded or calculated for each berry separately. Pol l e n for germination tests was c o l l e c t e d from the material grown i n the greenhouse. No p o l l e n storage was used for any of the pol l e n germination tests . . The fungicide used i n these experiments was captan 507o wettable powder (N-(trichloromethylmercapto)-4-cyclohexene-l,2-dicarboximide) . The con-centrations of captan used i n each experiment were expressed as ppm a c t i v e ingredient. Seed count study Samples of 10 secondary hand-pollinated be r r i e s from the greenhouse were - 10 -taken for estimations of achene v i a b i l i t y i n each berry. Berry weight was obtained and number of apparently sound and abortive achenes counted. Water was added and the samples were disintegrated i n a blender; the achenes that f l o a t e d were separated from those that sank and the two groups dried separately and then counted. Counts were made of the f l o a t i n g and sinking achenes from each berry. Germination tests were done on both groups for each sample i n p e t r i - d i s h moist-chambers. S t a t i s t i c a l analyses Analysis of variance was c a r r i e d out on the number of days required to ripen, berry weight, number of sound achenes, number of abortive achenes, number of t o t a l achenes, percentage of sound achenes per berry and berry weight per sound achene. Duncan's New Multiple Range Test as described by L i ( 1 4 ) was used to test differences among means. Covariance analysis was used to study the c o r r e l a t i o n between number of sound achenes and berry weight. A. Polle n germination tests 1. P o l l e n germination with captan i n the media Pollen was c o l l e c t e d from newly opened flowers of the v a r i e t i e s Northwest and S i l e t z , and dried i n the laboratory overnight. The po l l e n grains were cultured on sucrose-agar media (107 o sucrose and 0.757o agar) con-ta i n i n g captan i n concentrations of 0, 2 5 0 , 5 0 0 , 1000 ppm. ' The media were flowed into double-depression glass s l i d e s . Each s l i d e was placed on wet f i l t e r paper i n a p e t r i - d i s h as a moist-chamber and kept at room temperature o (22 C). Counting was done a f t e r 3 and 24 hours incubation. The - 11 -germination was recorded for 100 pollen grains in each of the depressions. The experiment was designed as a 2 x 4 factorial with two replicates in a completely randomized design; the double depression counts represented duplicate determinations within each replicate. 2. Pollen germination with captan on the media Pollen was collected from Northwest and Siletz plants soon after the dehiscence of anthers which usually took place at 9 to 10 a.m. and allowed to dry in the laboratory overnight. The medium used was 0.757 o agar con-taining 107o sucrose. The medium was flowed into double-depression glass slides and pollen grains were dusted finely over the medium. Each of the slides was placed on wet f i l t e r paper in a petri-dish as a moist-chamber. After one hour pollen incubation, the different concentrations of captan at 0, 500, 1000, 2 0 0 0 ppm in tap water were hand sprayed on the slides in a fine mist from an atomizer which was held about 25 cm away from the slides. Counting was done after 3 hours incubation in petri-dish moist-chambers at room temperature of 21.5-22°C- The germination percentage was obtained by counting 100 grains in each depression. The experimental design was a 2 x 4 factorial with two replicates in a completely randomized design; each depression represented a duplicate determination within each replicate. Pollen tube length was measured on 4 pollen grains in each treatment after 3 hours incubation. 3. Pollen germination with captan sprayed on undehisced anthers Captan concentrations of 0, 500, 1000 and 2000 ppm in tap water were sprayed on open flowers before the anthers had dehisced. Additional un-sprayed flowers were used as the control. Pollen was collected 3 hours after spraying and allowed to dry in the laboratory overnight. Pollen - 12 -grains from treated and untreated flowers were placed on 0.75% agar media containing 10% sucrose i n the wells of double-depression s l i d e s . Counting was done a f t e r 3 hours incubation i n p e t r i - d i s h moist-chambers at a room temperature of 22°C. The percent p o l l e n germination was recorded by counting 100 grains i n each depression. The experimental design was a 2 x 5 f a c t o r i a l i n a completely rando-mized design with two v a r i e t i e s , Northwest and S i l e t z , the 5 treatments, and the 2 petri-dishes as r e p l i c a t e s within each treatment. Each depression represented a duplicate determination within each r e p l i c a t e . 4. P o l l e n germination with captan sprayed on dehisced anthers Captan concentrations of 0, 500, 1000 and 2000 ppm i n tap water were sprayed on open flowers a f t e r the anthers had dehisced. There was also an unsprayed,control. The following morning, the flowers; were . c o l l e c t e d and the anthers taken o f f and allowed to dry i n the laboratory for 2 hours. P o l l e n grains from treated and untreated flowers were placed on 0.75%, agar media containing 10%, sucrose i n the wells of double-depression s l i d e s . Counting was done a f t e r 3 and 24 hours incubation i n p e t r i - d i s h moist-chambers at a room temperature of 21-22°C. The germination percentage was recorded by counting 100 grains i n each depression. The experiment was arranged as a completely randomized s p l i t - p l o t with the times of counting as the sub-plots. The main plots were Northwest and S i l e t z and the 5 treatments. The two petri-dishes were r e p l i c a t e s w i t h i n each treatment while depression counts represented duplicate determin-ations within each r e p l i c a t e . - 13 -B. Greenhouse experiments 1. Berry set with captan.sprayed on flowers before anther dehiscence Four d i f f e r e n t concentrations of captan at 0, 250, 500, 1000 ppm were applied on the tagged primary flowers i n which anthers were mostly un-dehisced. A f t e r 3 hours when the sprays had dried, s e l f - p o l l i n a t i o n was done by hand with p o l l e n grains from the same treated flowers. No spray was applied to the control flowers and they only received hand p o l l i n a t i o n with untreated pollen. The r e s u l t s were analysed by the analysis of variance for a randomized complete block design which included 5 treatments. Each block consisted of 5 pots i n which flowers could be found at a uniform stage of development. There were 5 blocks of S i l e t z and 3 blocks of Northwest. The data for the two v a r i e t i e s were analysed separately. 2. Berry set with captan sprayed on flowers a f t e r anther dehiscence Captan concentrations of 0, 500, 1000 and 2000 ppm were applied to the two secondary flowers from one c l u s t e r i n each plant using an atomizer. Most of the anthers i n these flowers were dehisced. The following morning, s e l f - p o l l i n a t i o n was done by hand with p o l l e n grains from the same treated flowers. The control was hand p o l l i n a t e d with p o l l e n from untreated flowers. The experiment was a v a r i a t i o n of the s p l i t - p l o t design with systematic arrangement of v a r i e t i e s as whole p l o t s . Each v a r i e t y had 10 blocks, and the 5 treatments were sub-plots. There were 2 flowers within each treat-ment and va r i e t y . 3. Comparison of spraying p i s t i l s versus anthers Two secondary flowers from one cl u s t e r i n each plant of the v a r i e t y Northwest were emasculated one day before opening. To treat p i s t i l s only, one of the emasculated flowers was sprayed with 1000 ppm of captan and a f t e r - 14 -the spray dried, p o l l i n a t e d with unsprayed p o l l e n grains. To treat anthers only, the other flower was not sprayed with captan but was p o l l i n a t e d with p o l l e n grains c o l l e c t e d from anthers that had been sprayed with 1000 ppm captan. The experiment had a randomized complete block design; with 18 plants as 18 blocks, sprayed p i s t i l s and sprayed anthers as 2 treatments. 4. Berry set i n p i s t i l s sprayed at i n t e r v a l s a f t e r p o l l i n a t i o n One secondary flower i n each plant was used for t h i s experiment. The flowers were emasculated one day before opening and the pollen was applied one day a f t e r emasculation. Captan at 1000 ppm was applied at time of p o l l i n a t i o n or 2, 4, or 6 days a f t e r p o l l i n a t i o n . The design was a v a r i a t i o n of the s p l i t - p l o t with systematic arrangement of v a r i e t i e s Northwest and S i l e t z as whole plo t s (13). There were 7 blocks of each v a r i e t y . The 4 times of spraying were the sub-plots. 5. Berry set i n p i s t i l s p o l l i n a t e d at i n t e r v a l s after, spraying The pair of secondary flowers from one c l u s t e r i n each plant were emasculated one day before opening. One flower of the pair was sprayed with 1000 ppm of captan one day a f t e r emasculation (corresponding to anthesis) and the other flower was not sprayed. Both emasculated flowers were hand-p o l l i n a t e d with untreated p o l l e n grains. The four p o l l i n a t i o n times were at anthesis, or 2, 4, or 6 days l a t e r . The experiment was a v a r i a t i o n of the s p l i t - s p l i t - p l o t with systematic arrangement of v a r i e t i e s Northwest and S i l e t z as whole plots (13). There were 7 blocks of each v a r i e t y . The 4 p o l l e n a p p l i c a t i o n s times were the sub-plots and sprayed and unsprayed p i s t i l s as the sub-units. - 15 -RESULTS Seed count study In preliminary t r i a l s , separating achenes by v i s u a l methods and by f l o t a t i o n gave s i m i l a r r e s u l t s . The percentage of germination of sinking achenes ranged between 60 and 100 per cent i n a l l the samples, while the f l o a t i n g achenes did not germinate. F l o a t i n g achenes were therefore described as abortive non-viable, and sinking achenes as sound and p o t e n t i a l l y v i a b l e . The v i s u a l method for counting achenes was therefore used i n a l l greenhouse experiments. The t o t a l achenes per berry was the sum of the number of abortive and sound achenes. A. P o l l e n germination tests 1. P o l l e n germination with captan i n the media No germination was obtained i n any of media containing captan at 2 5 0 , 500, 1000 ppm a f t e r either 3 or 24 hours incubation. The mean germination percentage i n the control a f t e r 3 hours incubation was 39? 0 for S i l e t z and 417o for Northwest. A f t e r 24 hours, i n control media the germination per-centage was increased to 457o i n S i l e t z and 477o i n Northwest. No a n a l y s i s of variance was c a r r i e d out on these data because there was no p o l l e n germination i n the media containing d i f f e r e n t captan concentrations. 2. P o l l e n germination with captan on the media The sprays were applied to the media a f t e r one hour po l l e n incubation and the percentage p o l l e n germination and the p o l l e n tube length were - 16 -recorded 2 hours later. The results showed that the mean percentage germination in the control (38%) and in the tap water sprayed media (44%,) were significantly greater than in the captan sprayed media, while the other 3 different concentrations of captan sprayed at 500, 1000, 2000 ppm . (9,5, and 4% respectively) did not differ significantly (Table 1). Neither the varieties nor the variety-treatment interaction were significant (P=.05). There were highly significant differences in the mean elongation of pollen tube among the treatments (Table 1). The mean length of pollen tube in the control and in the tap water sprayed media were significantly greater than in the 3 different captan concentrations at 500, 1000, 2000 ppm of captan sprayed media, but no significant differences were found among captan concentrations. - 17 -Table 1. Po l l e n germination as affe c t e d by captan sprayed on the media Treatment Mean percent pollen Mean pol l e n tube germination length (/(JO) Check 38 a 347 a Water sprayed 44 a 250 a Captan 500 ppm sprayed 9 b 74 b Captan 1000 ppm sprayed 5 b 51 b Captan 2000 ppm sprayed 4 b 43 b Standard error 3. .1 30. ,1 (Degrees of freedom) 10 4 Means i n the same column sharing the same l e t t e r did not d i f f e r s i g -n i f i c a n t l y according to Duncan's New Multiple Range Test (p=.05) - 18 -3. Pollen germination with captan sprayed on undehisced anthers The highly significant variety x treatment interaction (p=.0037) indicated that the varieties responded differently to the treatments (Table 2 ) . In the variety of Northwest, pollen germination was s i g n i f i -cantly reduced by both'500 ppm and 2 0 0 0 ppm captan (157o and 17» respectively). There were no significant differences among pollen from unsprayed, water sprayed, and 1000 ppm captan sprayed flowers in their mean percent pollen germination (377,, 427 c and 387 0 respectively) . The highest germination was found from water sprayed flowers. There was no significant difference in either variety between pollen from unsprayed and from 1 0 0 0 ppm captan sprayed flowers. As for the variety Siletz, only the 2 0 0 0 ppm'concentration sig n i f i c -antly reduced germination. There were no significant differences among the other treatments. - 19 -Table 2. P o l l e n germination as aff e c t e d by captan sprayed on undehisced anthers.^ Treatment Northwest S i l e t z Percentage Check 37 ab 31 abc Water sprayed 42 a 24 cd Captan 500 ppm sprayed 15 d 28 be Captan 1000 ppm sprayed 38 ab 35 abc Captan 2000 ppm sprayed 1 e 14 d Standard error 3.3 Degrees of freedom 10 Means sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's New Mu l t i p l e Range Test (p=.05) - 20 -4. Pollen germination with captan sprayed on dehisced anthers Pollen grains were collected from flowers sprayed after the anthers had dehisced. A low percentage of pollen germination was found even in the check ^Table 3 ) . There were highly significant differences in germination of pollen among the treatments. A significant reduction in the germination of pollen was found with sprays of 1000 ppm and 2000 ppm captan, but the reduction with 500 ppm was not significant. Unsprayed and water sprayed pollen did not differ significantly. The percentage of pollen germination after 24 hours ( 1 2 % ) was slightly but significantly higher than after 3 hours incubation (107o) . Northwest had a lower percentage of pollen germination than Siletz. While there were significant effects of varieties, treatments and incubations, only the treatment x incubation interaction was significant. It was caused by significant but small increases in the percent pollen germination from unsprayed and captan 500 ppm sprayed flowers after 24 hours pollen incubation. - 21 -Table 3. P o l l e n germination as a f f e c t e d by captan sprayed on dehisced 1 anthers Treatment Percentage Check 18 a Water sprayed 17 a Captan 500 ppm sprayed 12 ab Captan 1000 ppm sprayed 5 be Captan 2000 ppm sprayed 2 c Standard error " 1.9 (Degrees of freedom) 10 Variety Percentage Northwest 8 b S i l e t z 13 a Standard error 0.4 (Degrees of freedom) 10 Incubation period Percentage 3 hours 10 b 24 hours • 12 a Standard error 0.4 (Degrees of freedom) 10 Means i n the same column sharing the same l e t t e r did not d i f f e r s i g -n i f i c a n t l y according to Duncan's New M u l t i p l e Range Test (p=.05) - 22 -B. Greenhouse experiments 1. Berry set with captan sprayed before anther dehiscence As enough uniform primary flowers were obtained for only 3 blocks i n Northwest and 5 blocks i n S i l e t z , the data were analyzed separately for each v a r i e t y (Table 4). No malformation of f r u i t s was found i n either variety. In the va r i e t y Northwest, the r e s u l t s showed no s i g n i f i c a n t treatment e f f e c t s . In the v a r i e t y S i l e t z , no s i g n i f i c a n t e f f e c t s of the treatments were found upon the mean days required to ripen or the mean number of abortive achenes. Water, 250, 500 or 1000 ppm captan s i g n i f i c a n t l y decreased berry weight, sound achenes and t o t a l achenes per berry i n comparison with the controls. No s i g n i f i c a n t differences were found among the 3 captan concentrations and water. Water 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 captan sprayed at 500 or 1000 ppm i n i t s .effect upon the percentage of sound achenes per berry, and water gave a s i g n i f i c a n t decrease i n comparison with either control or the 250 ppm spray. The water spray i n S i l e t z r e s u l t e d i n s i g n i f i c a n t l y greater berry weight per sound achene than did any other treatment. Table 4. Berry set as affected by captan sprays before anther dehiscence •- -Variety Unsprayed Water sprayed Captan 250 ppm sprayed Captan 500 ppm sprayed Captan 1000 ppm sprayed 2 Standard error F p r o b a b i l i t y Days required Northwest 20 a 19 a 20 a 21 a 21 a 0.6 0.7113 to ripen S i l e t z 18 a 20 a 19 a 22 a 19 a 1.0 0.2086 Weight per Northwest 13.6 a 12.9 a 11.5 a 12.4 a 10.2 a " 0.7 0.2655 berry (g) S i l e t z 13.8 a 6.7 b 8.7 b 8.6 ,b 8.6 b 1.1 0.0030 Number of sound Northwest 196 a 154 a 159 a 101 a 68 a 25.5 0.1384 achenes per berry S i l e t z 257 a 45 b 96 b 78 b 93 b 20.9 0.0000 Number of abortive Northwest 136 a 180 a 129 a 177 a 215 a 28.4 0.4953 achenes per berry S i l e t z 87 a 145 a 144 a 179 a 131 a 22.3 0.1133 Total number of Northwest 332 a . 334 a 288 a 278 a 284 a 18.6 0.3403 achenes per berry S i l e t z 344 a 190 b 240 b 257 b 224 b 28.0 0.0156 Percentage of Northwest 58 a 50 a 55 a 36 a 25 a 7.9 0.2176 sound achenes S i l e t z 75 a 22 c 41 b 33 be 39 be 5.0 0.0000 per berry Berry weight Northwest 68 a 99 a 76 a 139 a 207 a 39 0.3424 per sound S i l e t z 55 . c 181 a 95 be 118 b 105 be 15 0.0005 achene (mg) Means i n the same row sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's New Multi p l e Test Range (p=.05) There were 8 degrees of freedom for error i n Northwest and 16 i n S i l e t z - 24 -2. Berry set with captan sprayed after anther dehiscence Berry development and set of achenes were significantly reduced when captan was sprayed on the flowers after anther dehiscence (Table 5). The proportion of mishappen fruits was increased with captan rate. Spraying with 2000 ppm captan significantly reduced the mean weight per berry, mean number of sound achenes per berry and the mean total number of achenes per berry. Captan sprays at 500 ppm or 1000 ppm were also found to significantly reduce these measures as compared with unsprayed control and water sprayed treatments. No significant differences were found between captan sprays at 500 ppm and 1000 ppm or between unsprayed control and water sprayed treatment. The mean number of abortive achenes per berry was significantly less with captan sprayed at 2000 ppm than with any other treatment. There were no significant differences among the other treatments in the mean number of abortive achenes per berry. The variety x treatment interaction was highly significant for the measure of mean percentage of sound achenes per berry. Siletz was more sensitive to the 500 ppm rate than was Northwest (Table 5,) , but both varieties had reduced sound achenes at 1000 or 2000 ppm. Captan at 1000 ppm and 2000 ppm significantly increased berry weight per sound achene in comparison with the unsprayed control, but not in comparison with water or 500 ppm captan. A highly significant correlation (r=0.78) existed between the number of sound achenes and berry weight. Table 5. Berry set as affected by captan sprays a f t e r anther dehiscence Unsprayed Water Captan sprayed 500 ppm sprayed Captan 1000 ppm sprayed Captan 2000 ppm sprayed Standard error p r o b a b i l i t y Days required to ripen Weight per berry (g) Number of sound achenes 26 a 5.0 a 96 a 27 a 27 a 4.4a 2.8 b 84 a 40 b 27 a 2.6 b 32 b 26 a 1.5 c 14 c 0.3 0.3 5.9 0.4077 0.0000 0.0000 Number of abortive achenes Total number of achenes Percentage of sound achenes - Northwest S i l e t z 52 a 148 a 60 ab 68 a 56 a 55 a 140 a 95 b 52 be 65 ab 41 cd 24 c 65 a 98 b 25 e 32 de 33 b 47 c 29 de 18 e 6.2 10.2 4.6 4.6 0.0095 0.0000 0.0054 0.0054 Berry weight per sound achene (Mg) 53 b 57 ab 84 ab 86 a 87 a 10.4 0.0458 Means i n the same row sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's New Multi p l e Test Range (p=.05) There were 72 degrees of freedom for error - 26 -3. Comparison of spraying p i s t i l s versus anthers Either p i s t i l s or anthers were sprayed with captan. P i s t i l s . sprayed with captan resulted in greater berry weight, more sound, and more total achenes per berry, and a higher percentage of sound achenes than where anthers were sprayed (Table 6). Spraying the p i s t i l s gave sig-nificantly lower berry weights per sound achene than did spraying the anthers. Ripening time and the mean number of abortive achenes per berry did not differ significantly between spraying p i s t i l s and spraying anthers. There was a highly significant correlation (r=0.75) between the number of sound achenes and berry weight. Table 6. The effect upon berry set of spraying p i s t i l s or anthers with captan Sprayed anthers Sprayed p i s t i l s Standard error probability Days required to ripen Weight per berry (g) Number of sound achenes per berry Number of abortive achenes per berry Total number of achenes per berry Percentage of sound achenes per berry Berry weight per sound achene (mg) 24 3.3 35 100 135 25 101 24 4.4 79 89 167 47 59 0.3 0.3 4.9 4.7 7.5 2.2 5.2 0.8594 0.0121 0.0000 0.0934 0.0065 0.0000 0.0000 ro There were 17 degrees of freedom for error - 28 -4. Berry set i n p i s t i l s sprayed at i n t e r v a l s a f t e r p o l l i n a t i o n A f t e r p o l l i n a t i o n , there was no s i g n i f i c a n t e f f e c t of time of spraying upon the number of days required to ripen or the number of t o t a l achenes per berry (Table 7). When p i s t i l s were sprayed with captan immediately a f t e r p o l l i n a t i o n , mean weight per berry, mean number of sound achenes per berry and mean percentage of sound achenes per berry were s i g n i f i c a n t l y reduced. The same treatments however s i g n i f i c a n t l y increased the mean number of abortive achenes per berry and mean berry weight per achene. Delays of 2, 4, or 6 days i n applying the spray gave s i m i l a r r e s u l t s for berry weight, number of sound and abortive achenes, percentage of sound achenes per berry, and berry weight per sound achene. There was a highly s i g n i f i c a n t c o r r e l a t i o n (r=0.83) between the number of sound achenes and berry weight. Table 7. Berry set with captan sprays at i n t e r v a l s a f t e r p o l l i n a t i o n Spraying days a f t e r p o l l i n a t i o n Standard F 0 2 4 6 error p r o b a b i l i t y Days required to ripen 23 a 22 a 23 a 23 a 0.4 0.7759 Weight per berry (g) 3.5 b 4.9 a 5.4 a 5.2 a 0.4 0.0036 Number of sound achenes per berry 42 b 84 a 100 a 103 a 6.6 0.0000 Number of abortive achenes per berry 97 a 63 b 67 b 59 b 6.5 0.0006 Tota l number of achenes per berry 139 a 146 a 168 a 162 a 10.0 0.1806 Percentage of sound achenes per berry 28 b 56 a 59 a 63 a 2.7 0.0000 Berry weight per sound achene (mg) 122 a 63 b 56 b 50 b 15.8 0.0101 Means i n the -same row sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's New Mult i p l e Range Test (p=.05) There were 36 degrees of freedom for error - 30 -5. Berry set in p i s t i l s pollinated at intervals after spraying Where p i s t i l s were sprayed at anthesis and pollinated at intervals thereafter, berry set data indicated significant differences among pollination treatments and captan sprays. The interactions variety x pollination and pollination x captan were also, significant in most cases. That p i s t i l s of Northwest remained receptive longer than those of Siletz was indicated by several significant variety x pollination interactions (Table 8). These interactions were significant for a l l f r u i t set variables measured except ripening. Fruit set in Siletz was greatly reduced when pollination was with-held until 4 or 6 days after spraying, but in Northwest pollination a moderate reduction was observed at 4 days and a greater reduction at 6 days (Table 8). The effects of captan sprays were compared within the same p o l l i -nation treatment (Table- 9). Spraying significantly decreased the number of sound achenes per berry only when pollination was done at anthesis or 2 days later.- Significantly more abortive achenes per berry were obtained in sprayed p i s t i l s than in unsprayed p i s t i l s when pollination was applied at anthesis. No significant effect of spraying was found when pollination was done at 4 or 6 days after anthesis. There were no significant effects at any one pollination time upon ripening or berry weight, although the mean effect of spraying was significant for berry weight. Captan sprays at anthesis also decreased the percentage of sound achenes and increased berry weight per sound achene. There was a highly significant correlation (r=0.72) between the number of sound achenes and berry weight. Table 8. E f f e c t s upon berry set of p o l l i n a t i o n at i n t e r v a l s a f t e r spraying Variety P o l l i n a t i o n days a f t e r spraying Standard F 0 2 4 6 error p r o b a b i l i t y Days required to Northwest 25 a 26 a 26 a 26 a 0.4 0.3464 ripen S i l e t z 23 a 24 a 25 a 25 a 0.4 0.3464. Weight per berry Northwest 4.4 a 4.9 a 3.0 b 0.7 c 0.4 0.0026 (g) S i l e t z ' 4.4 a 5.3 a 0.3 b 0.2 b 0.4 0.0026 Number of sound Northwest 63 a 75 a 36 b 7 c 4.5 0.0206 achenes per berry S i l e t z 80 a 87 a 5 b 2 b 4.5 0.0206 Number of abortive Northwest 99 a 86 ab 64 b 18 c 9.6 0.0030 achenes per berry S i l e t z 84 b 109 a 9 c 9 c 9.6 0.0030 Total number of Northwest 162 a 160 a 101 b 25 c 13.5 0.0007 achenes per berry S i l e t z 164 a 195 a 14. b 11 b 13.5 0.0007 Percentage of Northwest 38 ab 45 a 28 b 12 c 4.0 0.0015 sound achenes S i l e t z 47 a 43 a 4 b 1 b 4.0 0.0015 per berry Berry weight per Nor thwe s t 94 a 78 a 86 a 39 b 11.6 0.0290 sound achene (mg) S i l e t z 69 a 75 a 11 b 7 b 11.6 0.0290 Means i n the same row sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's New Multiple Range Test (p=.05) There were 36 degrees of freedom for error. - 32 -Table 9. The reaction of captan sprayed p i s t i l s to pollination at intervals after spraying''" Pollination days after spraying 0 2 4 6 Mean Days required Unsprayed 24 25 25 25 25 to ripen Sprayed 24 25 25 25 . 25 S.E.2 N.S. N.S. N.S. N.S. N.S. Weight per Unsprayed 5.2 5.5 2.1 0.5 3.3 berry (g) Sprayed 3.6 4.7 1.2 0.4 2.5 S.E. N.S. N.S. N.S. N.S. 0.2 Number of sound Unsprayed 105 94 27 5 58 achenes per berry Sprayed 37 68 14 4 31 S.E. 5.5 5.5 N.S. N.S. 2.7 Number of abortive Unsprayed 63 95' 51 23 62 achenes per berry Sprayed 120 100 22 4 58 S.E. 8.0 N.S. N.S. N.S. N.S. Total number of Unsprayed 168 189 78 28 116 achenes per berry Sprayed 158 167 37 8 92 S.E. N.S-. N.S. N.S. N.S. 5.3 Percentage of Unsprayed 62 48 21 6 34 sound achenes per Sprayed 23 40 12 8 21 berry S.E. 3.2 N.S. N.S. N.S. 1.6 Berry weight per Unsprayed 51 67 53 32 50 sound achene (mg) Sprayed 111 86 44 15 64 S.E. 8.3 N.S. N.S. N.S. 4.1 Standard errors (S.E.) were given only when p< .05 There were 48 degrees of freedom for error - 33 -DISCUSSION A. Pollen germination tests 1. Pollen germination with captan in the media Concentrations at 250, 500 and 1000 ppm captan completely inhibited germination after 3 hours incubation when these different concentrations were contained in the germination media. Toxic effects of captan on pollen did not disappear during prolonged germination up to 24 hours. This finding supports the work of Rich (26) with apple pollen, Shawa e_t a l (28) with cranberry and Braun et al_ (2) with apple and pear pollen. They found that the several rates of captan from 10 ppm to 1000 ppm a l l prevented pollen germination when contained in the germination media. Rich (26) indicated that the in vitro method of soaking the pollen in fungicide solution was too severe as the fungicide probably did not come into contact with pollen grains in this manner under natural conditions. 2. Pollen germination with captan on the media Captan inhibited further development of germinated pollen and arrested the elongation of pollen tubes when sprayed on the media after one hour of pollen incubation. These results suggested that strawberry pollen may be arrested in development by direct contact with captan at any time during i t s development. 500 ppm captan showed the same degree of inhibition of percentage of pollen germination and elongation of pollen tubes as 1000 ppm and 2000 ppm of captan. However, Eaton (7) found that 1000 ppm of captan reduced sweet cherry pollen germination and pollen tube elongation when captan was sprayed on the germination media. The other treatments 100 ppm, - 34 -10 ppra and 1 ppm of captan and the control did not differ significantly in their mean percentage of pollen germination. Thus probably the concentrations of captan were too low to prevent pollen germination. 3. Pollen germination with captan sprayed on undehisced anthers Pollen germination was unaffected by captan when sprayed on the undehisced anthers except at the relatively high rate of 2000 ppm. This implies that the undehisced anther wall in strawberry amply protects pollen from contact with the fungicide both before and after dehiscence. This is similar to the findings of Shawa e_t al (28) , Lockhart (15) and Dhuria et al_ (6) but contrasts with the situation reported by Eaton (8) for apple where spraying before anther dehiscence reduced later germination possibly because of a mixing of fungicides from the anther wall with the pollen during dehiscence. 4. Pollen germination with captan sprayed on dehisced anthers Pollen germination was also reduced when captan was sprayed on the dehisced anthers. The inhibition of pollen germination increased as the rate of captan increased. This also indicated that captan prevents germination by direct contact with pollen. Prolonged incubation time did not much increase the percent pollen germination. This also suggests that the effect of captan was not a transitory one. Cristoferi e_t a_l (4) found that fungicides reduced apple pollen germination when applied at f u l l anthesis. Lockhart (15) and Dhuria e_t a l (6) indicated that pollen germination was reduced when pollen was collected from sprayed plants or from open pollen sacs which had been thoroughly wetted with spray. Con-sidering the effects of fungicides on pollen germination under orchard conditions, the findings of Rich (26) were different from those of Schmidt (27). These differences in captan effect may be due to the different - 35 -stage of anther development a t the time of spraying. B. Greenhouse experiments Days required to ripen There was no s i g n i f i c a n t e f f e c t of captan sprays upon the period from flower opening to berry maturity. Variations i n number of days for berry ripening were found among various experiments when plants were grown i n the greenhouse. This might be due to d i f f e r e n t temperatures during the several growing periods. Berry weight and number of achenes There was a highly s i g n i f i c a n t c o r r e l a t i o n between berry weight and number of sound achenes i n each greenhouse experiment. The development of the strawberry receptacle was influenced by the number of sound achenes per berry as w e l l as the percentage of sound achenes per berry. Berry weight per sound achene was increased as the number of sound achenes per berry decreased. Perhaps achenes were exerting an e f f e c t i n v o l v i n g auxin-l i k e growth substances as described by Nit s c h (22) , and Tukey (29) and Moore (21). . Way (32) has recently a r t i c u l a t e d the generally accepted view that adequate p o l l i n a t i o n and f e r t i l i z a t i o n are required for normal f r u i t development. Darrow (5) also indicated that p o l l i n a t i o n of a l l p i s t i l s of the strawberry flower was necessary for maxium berry s i z e . 1. Berry set with captan sprayed before anther dehiscence The anther tissue of the Northwest v a r i e t y did not appear to absorb the captan since the berry weight and achenes set were not reduced by captan sprayed on undehisced anthers. However, the anther tissue of S i l e t z v a r i e t y appeared to s l i g h t l y absorb the captan since the berry weight - 36 -and achene set were reduced by captan sprays. E a r l i e r reports implied that p o l l e n germination was unaffected by captan when sprayed on the un-dehisced anthers. The r e s u l t s of berry set also indicated that the undehisced anther wall may protect strawberry pollen from contact with the fungicide. 2. Berry set with captan sprayed a f t e r anther dehiscence Captan sprays applied to the flowers a f t e r anther dehiscence s i g -n i f i c a n t l y reduced berry weight and achene set. Serious reduction of berry development caused f r u i t malformations. These r e s u l t s support those of Bennett (1) who observed that the proportion of misshapen f r u i t s was increased when fungicide sprays were applied to strawberry flowers of Sovereign v a r i e t y , but Talisman v a r i e t y was l i t t l e a f f e c t e d . P o l l e n germination tests also showed that captan reduced p o l l e n germination when captan was sprayed on the dehisced anther (Table 3). Schmidt (27) with pear, plum and apple, Rich (26) with apple, Braun et a l (3) with apple and Kaspers (12) with apple found no s i g n i f i c a n t e f f e c t on f r u i t set when captan was sprayed into the open blossom under orchard conditions, but Shawa et: al_ (28) found that cranberry y i e l d was s i g n i f i c a n t l y reduced when captan was sprayed during the blossoming period i n the f i e l d . 3. Berry set with captan sprayed on p i s t i l s or anthers Berry set was greatly reduced when emasculated flowers were a r t i f i c i a l l y p o l l i n a t e d with p o l l e n from sprayed anthers as compared with sprayed p i s t i l s and a r t i f i c i a l l y p o l l i n a t e d with unsprayed p o l l e n (Table 6). These r e s u l t s support those of Braun e_t al_ (3) who reported that no female apple flower parts were damaged by captan, but i n greenhouse t r i a l s , when the flowers were a r t i f i c i a l l y p o l l i n a t e d with sprayed pollen , f r u i t set - 37 -was greatly reduced. Schmidt (27) found that captan did not damage the stigmas. However, Rich (26) concluded that no male or female parts of the flowers were affected by captan because that fungicide had no serious effect on f r u i t set when either p i s t i l s or anthers were sprayed with captan. 4. Berry set in p i s t i l s sprayed at intervals after pollination A significant reduction of berry weight and achene set was caused by the captan sprayed on emasculated flowers immediately after pollination. These results were similar to the findings of MacDaniels (17, 19). In this experiment captan had no affect on berry development when sprays were applied 2, 4 and 6 days after pollination. Darrow (5) indicated that the reaction to f e r t i l i z a t i o n was quite rapid sometimes within as short a time as 24 to 48 hours. The pollen grains had already entered the styles and escaped the fungicide when captan was applied 2, 4 and 6 days after pollination. Small berries could be obtained from the emasculated flowers when the flowers were sprayed immediately after pollination, and this f r u i t probably was due to some of the pollen grains lodged between the papillae of the stigma and escaping the fungicide. 5. Berry set in p i s t i l s pollinated at intervals after spraying Where p i s t i l s were pollinated at anthesis and sprayed with captan the berry weight and achene set were significantly reduced as compared with p i s t i l s which were not sprayed. This result also indicated that straw-berry pollen is prevented in development by direct contact with captan. Captan did not affect receptivity of p i s t i l s as shown by fr u i t set since either p i s t i l s sprayed or not sprayed with captan could remain recptive up to 2 days after anthesis in the greenhouse. That strawberry p i s t i l s - 38 -may remain receptive for several days in the f i e l d was shown by Moore (21). He found that strawberry p i s t i l receptivity was greatly reduced after 168 hours under warm conditions, but cool temperatures tended to slow down the physiological ageing of the p i s t i l s and they remained receptive for longer periods of time. Darrow (5) also reported that strawberry blossoms might remain receptive for even ten days in cool weather i f not pollinated. Berry weight and achene set were reduced in greenhouse t r i a l s by captan as reported here. It would seem that under specific circumstances berry set could be reduced in the f i e l d . This probably would not always occur and would be d i f f i c u l t to demonstrate as captan did not injure p i s t i l s or their receptivity and p i s t i l s can remain receptive for several days in the f i e l d . While captan could affect pollen germination during spraying, bees probably could get sufficient unsprayed pollen from later opening flowers to allow f r u i t set. Probably only some flowers, a proportion of those at anthesis which had not been pollinated at time of spraying ,would be damaged. - 39 -REFERENCES 1. Bennett, M. 1968. Strawberry f r u i t malformation. II Role of disease and fungicides. Ann. Rept. East Mailing Res. Sta. for 1967, 204-5. 2. Braun, H., and Schbnbeck, F. 1963. Untersuchungen Uber den Einfluss von Pflanzenschutzpraparaten auf die Keimung von Apfel -und Birnenpollen. ErwObstb. _5, 170-71. 3. Braun, H., and SchOnbeck, F. 1965. Untersuchungen Uber den Einfluss verschiedener PflanzenschutzprMparaten auf die Befruchtung von Apfelbaumen. ErwObstb. 7_, 26-8. 4. Cristoferi, G. et. a l . 1966. The effects of fungicidal treatment during flowering on some fr u i t trees. Hort. Abs. 1967. 37_, 746. 5. Darrow, G. M. 1966. The strawberry. Holt, Rinehart and Winston Inc. New York, Chicago, San Francisco, p.342. 6. Dhuria, H.S., Hanser, H., and Buchloh, G. 1965. Untersuchungen Uber den Einfluss des Insektizids Thiodan auf Pollenkeimung und Fruchtansatz beim Apfel. ErwObstb. 7_, 21-6. 7. Eaton, G. W. 1961. Germination of sweet cherryv(Prunus avium L.) pollen in vitro as influenced by fungicides. Can. J. Plant Sci. 41, 740-43. 8. Eaton, G. W. 1963. Germination of apple pollen as influenced by captan sprays. Proc. Amer. Soc. Hort. Sci. 83, 101-6. 9. Freeman, J. A. 1964. The control of strawberry f r u i t rot in coastal British Columbia. Can. Plant Pis. Surv. 44, 96-104. - 40 -10. GMrtel, W. 1961. Eingluss der im Weinbau gebrHuchlichen Pflanzenschutzmittel auf Keimung und Schlauchwachstum bei Rebpollen. M i t l . B i o l . Bundesanst., B e r l i n Dahlem, H. 104, 108-112. 11. Gourley, C. 0. 1968. Fungicidal control of B o t r y t i s cinerea on four strawberry v a r i e t i e s . Can. J . Plant S c i . 48, 267-72. 12. Raspers, H. 1965. Sind BlUtespritzungen mit organischen Fungiziden im Kernobstbau bedenklich? ErwObstb. 7, 28-31. 13. LeClerg, E. L., Leonard W. H. and Clark A. G. 1966. F i e l d p l o t technique. Burgess Publishing Company. Minneapolis, Minnesota, p..194-95. 14. L i , J. CR. 1964. S t a t i s t i c a l Inference. Vol.1. Edwards Brothers Inc. Ann Arbor, Michigan p.270-73. 15. Lockhart, C. L. 1967. E f f e c t of fungicides on germination of lowbush blueberry p o l l e n and on number of seeds per berry. Can.Plant  P i s . Surv. 47, 72-3. 16. MacDaniels, L.H., and Furr, J . R. 1930. The e f f e c t s of dusting sulphur upon the germination of the pol l e n set of f r u i t of the apple. N. Y. (Cornell) A g r i c . Exp. Sta. B u l l . No. 499. 17. MacDaniels, L. H., and B u r r e l l , A. B. 1934. The e f f e c t of sulphur fungicides applied during the bloom, on the set of apple f r u i t s . Phytopath. 24, 144-50. 18. MacDaniels, L. H., and Hildebrand, E. M. 1938. Results of further studies on the e f f e c t of bactericides on pollen germination and f r u i t set. Proc. Amer. Soc. Hort. S c i . 35, 14-23. 19. MacDaniels, L. H., and Hildebrand, E. M. 1938. The e f f e c t of copper compounds applied to spur units during bloom upon the set of apple f r u i t s . Proc. Amer. Soc. Hort. S c i . 36, 230-33. - 41 -20. MacDaniels, L. H., and Hildebrand, E.M. 1940. A study of pol l e n germination upon the stigmas of apple flowers treated with fungicides. Proc. Amer. Soc. Hort. S c i . 37, 137-40. 21. Moore, J . N. 1964. Duration of r e c e p t i v i t y to p o l l i n a t i o n of flowers of the high bush blueberry and the c u l t i v a t e d strawberry. Proc. Amer. Soc. Hort. S c i . 85, 295-301. 22. Nitsch, J.P. 1950. Growth and morphogenesis of the strawberry as rel a t e d to auxin. Amer. J. Bot. 37, 211-15. 23. Powelson, R. L. 1960. I n i t i a t i o n of strawberry f r u i t r o t caused by B o t r y t i s cinerea. Phytopath. 50, 491-94. 24. Powell, D. 1954. The e f f e c t of captan on gray mold r o t incidence and y i e l d of strawberry. Plant P i s . Rep. 38, 209-11. 25. Remy, P. 1953. Contribution a l'etude du pollen des arbres f r u i t i e r s a noyau, genre prunus. Ann. Inst. Nat. Recherche agron. Serie B. Ann. Amelioration des Plantes. 3_, 351-378. 26. Rich, A. S. 1957. E f f e c t of various fungicides applied during bloom on apple p o l l i n a t i o n and f r u i t set. Agr. Chem. 12(6) T 64-6. 27. Schmidt, T. 1956. Untersuchungen liber die Beeinflussung der Pollenkeimung durch Spritzung i n die BlUte und ihre Auswirkung i n der Praxis. P f l s c h . Ber. Wien. 16, 75-9. 28. Shawa, A. Y., Doughty, C. C., and Johnson, F. 1966. E f f e c t of fungicides on McFarlin cranberry pollen germination and f r u i t set. Proc. Amer. Soc. Hort. S c i . 89, 255-58. 29. Tukey, R. B. 1952. Some p h s i o l o g i c a l factors i n f l u e n c i n g the growth and development of strawberry f r u i t s . Ph.D. thesis Cornell Univ. - 42 -30. Vangham, E. K. 1960. Influence of fungicides on micro-organisms associated with apparently healthy strawberries. . Phytopath. 50, 657-58. 31. Watson, D. P. 1952. E f f e c t of E l g e t o l sprays on p i s t i l s of apple flowers. . Proc. Amer. Soc. Hort. S c i . 60, 151-54. 32. Way, D..W. 1968. Strawberry f r u i t malformation. I. Pomological aspects. Ann. Rept. East M a i l i n g Res. Sta. for 1967. 199-203. 5 - 43 -A P P E N D I X - 44 -Table 10. ~F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on the media Source of variance Degrees of freedom Levels of s t a t i s t i c a l significance percent pollen Length of pollen germination tube Q>) Variety Treatment Variety x treatment Replicates within varieties and treatments Wells within replicates, varieties and treatments Total (v-1) (t-1) (v - l ) ( t - l ) vt(r-l) vtr (w-1) vtrw-1 1 4 10 20 39 0.2473 0.0000 0.3238 0.0186 0.3041 0.0082 - 45 -Table 11. F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on the undehisced anthers Source of variance Degrees of freedom Levels of s t a t i s t i c a l significance Variety Treatment Variety x treatment Replicates within varieties and treatments Wells within replicates, varieties and treatments Total (v-1) (t-1) ( v - l ) ( t - l ) vt(r-l) vtr (w-1) vtrw-1 1 4 4 10 20 39 0.6415 0.0001 0.0037 0.1271 - 46 -Table 12. F-probability from the analysis of variance for pollen germination as affected by captan sprayed on the dehisced anthers Source of Variance Degrees of freedom Levels o.f s t a t i s t i c a l significance Variety Treatment Variety x treatment Replicates within varieties and treatments Wells within replicates, varieties and treatments Incubation Incubation x variety Incubation x treatment Incubation x variety x treatment Incubation x replicates within varieties and treatments Error Total (v-1) (t-1) (v-1) (t-1) vt(r-l) vtr (w-1) ( i - l ) (i-l)(v-1) ( i - l ) (t-1) (i-l)(v-1)(t-1) v t ( i - l ) ( r - l ) vtr(i-i)(w-1) vtrwi-1 1 4 4 0.0175 0.0007 0.1065 10 0.2196 20 0.0005 1 0.0038 1 0.5392 4 0.0497 4 0.2641 10 0.4963 20 79 Table 13. F-probabilities from the analysis of variance for berry set as affected by captan sprays before anther dehiscence Northwest Source of Degrees of variance freedom Levels of s t a t i s t i c a l significance Days per berry No.of sound No. of No.of total Percentage Berry Wt. required weight (g) achenes per abortive achenes per of sound per sound to ripen berry achenes berry achenes achene per berry per berry (mg) Siletz Block (b-1) 2 0.7946 Treatment (t-1) 4 0.7113 Error (b-1) (t-1) 8 Total bv-1 14 0.035 0.2655 0.5563 0.1384 0.8402 0.4953 0.1636 0.3403 Block (b-1) 4 0.6245 Treatment (t-1) 4 0.2086 Error (b-1)(t-1) 16 Total bv-1 24 0.4310 0.0300 0.5439 0.0000 0.0752 0.1133 0.4617 0.0156 0.9270 0.2176 0.0391 0.0000 0.3769 0.3424 0.0759 0.0005 Table 14. F-probabilities from the analysis of variance for berry set as affected by captan sprays after anther dehiscence Levels of s t a t i s t i c a l significance Source of Degrees of Days per berry . No. of sound No. of No.of total Percentage Berry Wt. variance freedom required weight (g) achenes per abortive achenes per of sound per sound to ripen berry achenes berry achenes achene per berry per berry (mg) Whole plot (bv-1) Treatment (t-1) 19 0.0000 4 0.4077 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0095 0.0000 0.0691. 0.0742 0.0000 0.0458 Variety x treatment (v-1)(t-1) 4 0.0808 Experimental error v(t-l)(b-1) Fruits/ error Total tbv(f-l) bvtf-1 72 0.0000 100 199 0.2515 0.0000 0.1690 0.0000 0.7839 0.0000 0.3467 0.0000 0.0054 0.2909 0.0143 0.1143 Since the main plots (varieties) were in rows, inferences were restricted to treatments and the variety x treatment interaction (13) Table 15. F - p r o b a b i l i t i e s from the analysis of variance for berry set a f t e r spraying either p i s t i l s or anthers Source of Degrees of Days per berry No. of sound No. of variance freedom required weight (g) achenes per abortive to ripen berry Levels of s t a t i s t i c a l s i g n i f i c a n c e No.of t o t a l Percentage Berry Wt. achenes per of sound per sound achenes berry achenes achene per berry per berry (mg) Block (b-1) .17 0.2484 Treatment (t-1) 1 0.8594 Error (b-1)(t-1) 17 Total bt-1 35 0.3239 0.0121 .0.4377 0.0000 0.0131 0.0934 0.0914 0.0065 0.3412 0.0000 0.0883 0.0000 Table 16. F-probabilities from the analysis of variance for berry set when p i s t i l s were sprayed at intervals after pollination Levels of s t a t i s t i c a l significance Source of Degrees of Days per berry No. of sound No. of Nd,.of total Percentage Berry Wt. variance freedom required weight (g) achenes per abortive achenes per of sound per sound to ripen berry achenes berry achenes achene per berry per berry (mg) Whole plot vb-1 Treatment (t-1) Variety x treatment (v-1)(t-1) Error Total v(b-l)(t-1) vtb-1 13 0.0071 3 0.7759 3 0.2647 36 55 0.0315 0.0036 0.5225 0.0553 0.0000 0.1327 0.1637 0.3707 0.0173 0.5608 0.0006 0.1806 0.0101 0.0000 0.1683 0.0697 0.0376 0.1276 Since the main plots (varieties) were in rows, inferences were restricted to treatments and the variety x treatment interaction (13) Table 17. F-probabilities from the analysis of variance for berry set in p i s t i l s pollinated at intervals after anthesis Source of Degrees of variance freedom Whole plot bv-1 Pollination (p-1) Variety x pollination (v-l)(p-l) Experimental error v(b-l)(p-1) Captan Variety x captan Pollination x captan (c-1) (c-1)(v-1) (p-1)(c-1) Variety x pollination (v-1)(p-1) x captan (°-l) Error vp(b-l)(c-1) To tal bvps-1  Levels of s t a t i s t i c a l significance Days per berry No.-of sound No. of • No. of total Percentage Berry Wt. required weight (g) achenes per abortive achenes per bf sound per sound to ripen berry achenes berry achenes achene per berry per berry (mg) 13 0.000,0 3 0.0014 3 0.3464 36 0.0266 1 0.1015 1 0.9505 3 0.4464 3 0.5633 48 111 0.0024 0.0000 0.0026 0.0273 0.0004 0.2187 0.1281 0.4515 0.0538 0.0000 0.0206 0.0063 0.0000 0.8065 0.0000 0.7348 0.3635 0.0000 0.0030 0.1288 0.5337 0.0745 0.0000 0.6705 0.2057 0.0000 0.0007 0.0616 0.0034 0.2506 0.5307 0.6837 0.0119 0.0000 0.0015 0.0838 0.0000 0.3958 0.0000 0.7742 0.0000 0.0000 0.0290 0.0138 0.0221 0.2293 0.0000 0.8221 Since the main plots (varieties) were in rows, inferences were restricted to treatments and the variety x treat-ment interaction (13) 

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