Effect of Captan on Pollen Germination and Fruit Set In
EFFECT OF CAPTAN ON POLLEN GERMINATION AND
FRUIT SET IN STRAWBERRY
by
LIANG-ING CHEN
B.Sc. Taiwan Provincial 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
in the Division
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 inhibit pollen germination when included in or sprayed on the germination medium, or when sprayed on anthers after pollen dehiscence. Toxic effects did not disappear during prolonged germination. However, pollen germination was slightly affected by captan sprayed on the undehisced anthers.
When open flowers were sprayed before anther dehiscence, berry set was reduced in the variety Siletz but not in the variety Northwest.
When sprayed after anther dehiscence, achene set, and berry development were decreased. The proportion of mishappen fruits increased with
captan concentration. Pollination from sprayed anthers was not as
effective in fruit setting as control pollination of sprayed pistils.
Sprays applied to pistils either just before or just after pollination
decreased fruit set. Fruit set was not affected by sprays one day after pollination. Captan therefore seemed to act directly upon pollen
germination and not upon the receptivity of the stigma or upon pollen
tube growth in the style or upon fertilization. In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.
I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.
Division of Plant Science
The University of British Columbia
Vancouver 8, B.C. Canada
December, 1968. ACKNOWLEDGMENTS
I wish to thank Dr. G. W. Eaton, Associate Professor, Division of
Plant Science, University of British Columbia, for his guidance and
supervision during planning, experimental phases and final reporting of
this thesis, as well as his continuous encouragement.
Acknowledgment is also extended to the other members of my thesis
committee:
Dr. V. C. Brink, Division of Plant Science
Dr. A. J. Renney, Division of Plant Science
Dr. C. A. Hornby, Division of Plant Science
Dr. D. P. Ormrod, Division of Plant Science
The Canada Department of Agriculture, Research Station, Agassiz,
B.C. provided the initial strawberry plants used in this project.
My special thanks to D. Armstrong and A. Battensby for their help
in growing strawberry plants in the field.
The research was supported in part by National Research Council
operating grant A2023 awarded to Dr. G. W. Eaton. - iv -
TABLE OF CONTENTS
Page
I. INTRODUCTION 1
II. LITERATURE REVIEW 2
A. Effect of fungicides on pollen germination and fruit set 2
B. Seed count in strawberry 6
C. The control of strawberry fruit rot 7
III. MATERIALS AND METHODS 9
Seed count study 9
Statistical analyses 10
A. Pollen germination tests 10
1. Pollen germination with captan in the media .... 10
2. Pollen germination with captan on the media .... 11
3. Pollen germination with captan sprayed on undehisced anthers 11
4. Pollen 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 after
anther dehiscence 13
3. Comparison of spraying pistils versus anthers . . . 13
4. Berry set in pistils sprayed at intervals after pollination 14 5. Berry set in pistils pollinated at intervals after spraying 14
IV. RESULTS 15 - V -
Page
Seed count study 15
A. Pollen germination 15
1. Pollen germination with captan in the media ... 15
2. Pollen germination with captan on the media ... 15
3. Pollen germination with captan sprayed on undehisced anthers . 18
4. Pollen 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 after
anther dehiscence . 24
3. Comparison of spraying pistils versus anthers . . 26
4. Berry set in pistils sprayed at intervals after pollination ..... 28 5. Berry set in pistils pollinated at intervals after spraying ...... 30
V. DISCUSSION 33
A. Pollen germination tests . 33
1. Pollen germination with captan in the media ... 33
2. Pollen germination with captan on the media ... 33
3. Pollen germination with captan sprayed on undehisced anthers 34
4. Pollen germination with captan sprayed on
dehisced anthers 34
B. Greenhouse experiments 35
Days required to ripen . 35
Berry weight and number of achenes 35 - vi -
Page
1. Berry set with captan sprayed before anther dehiscence 35
2. Berry set with captan sprayed after anther dehiscence ..... 36
3. Berry set with captan sprayed on pistils or anthers 36
4. Berry set in pistils sprayed at intervals after pollination 37
5. Berry set in pistils pollinated at intervals
after spraying 37
VI. REFERENCES 39
VTI. APPENDIS 43 - vii
LIST OF TABLES Page Table 1. Pollen germination as affected by captan sprayed on the media 17
Table 2. Pollen germination as affected by captan sprayed on undehisced anthers 19
Table 3. Pollen germination as affected by captan sprayed on dehisced anthers ... 21
Table 4. Berry set as affected by captan sprays before anther dehiscence . 23
Table 5. Berry set as affected by captan sprays after anther dehiscence ...... 25
Table 6. The effect upon berry set of spraying pistils or anthers with captan ...... 27
Table 7. Berry set with captan sprays at intervals after pollination 29
Table 8. Effects upon berry set of pollination at intervals after spraying 31
Table 9. The reaction of captan sprayed pistils to pollination at intervals after spraying ... 32
Table 10. F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on the media 44
Table 11. F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on undehisced anthers ...... 45
Table 12. F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on dehisced anthers 46
Table 13. F-probabilities from the analysis of variance for berry set as affected by captan sprays before anther dehiscence 47
Table 14. F-probabilities from the analysis of variance for berry set as affected by captan sprays after anther dehiscence 48 - viii
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
Various fungicide sprays are recommended for controlling common tree- fruit diseases using at least 3 or 4 applications during blossom. Little information is available concerning the effects of these sprays on the physiology of pollen germination and fruiting.
Several workers have indicated that low tolerances of tree-fruit pollen grains to fungicides or other pesticides can result in reduced pollen germination in laboratory tests when applied in vitro or in the orchard during bloom. There are contradictory reports however concerning the importance of these effects in relation to fruit-setting.
The present greenhouse studies with strawberry flowers were designed to test whether the fungicide captan (N-(trichloromethylmercapto)-4-cyclohexene-
1,2-dicarboximide) will inhibit strawberry pollen germination and whether this might affect the development of achenes and related receptacle tissue.
Captan is commonly used during bloom to control apple scab and brown rot of stone fruits as well as grey mold of raspberry and strawberry.
Therefore, although the strawberry in a convenient test plant, the results may have wider implications. - 2 -
LITERATURE REVIEW
A. Effect of fungicides on pollen,germination and fruit set
Studies on the effect of fungicides applied to the open blossoms on
fruit set date from the use of Bordeaux and sulphur fungicides for con•
trolling apple scab. MacDaniels and Furr (16) found in 1930 that sulphur
dust lodging on the stigmas of apple blossoms could prevent pollen germ•
ination and reduce or prevent fruit set. They stated that the practical
effect of dusting blossoms may or may not be a reduction of fruit set,
depending on the time of dust application with reference to pollination, weather conditions and the number of fruits per spur. MacDaniels and
Burrell (17) indicated that the greatest reduction in fruit set was caused
by applications of sulphur dust and lime-sulphur spray 24 hours before
pollination and the next greatest by applications of these fungicides
coincident with pollination.
A further effect of several copper containing bactericides was found
by MacDaniels and Hildebrand (18). They found that all treatments reduced
the percentage of pollen germination and the length of the pollen tube when
the bactericides were applied to the surface of sucrose-agar media by
using a small duster or an atomizer, but did not seriously cut down fruit
set when applied to the blooming trees. They came to the conclusion that
the pollen grains might lodge in between the papillae of the stigma and
were not in contact with dust particles or wet by sprays. MacDaniels
and Hildebrand (19) found that application of copper compounds to the stigmas
of apple blossoms had not given the expected results in reducing the fruit
set. They indicated that it was probably related to the location of the - 3 -
pollen grains upon the papillae of the stigma with relation to the grains
of copper lime dust and the failure 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 fruit setting process and the many factors involved.
MacDaniels and Hildebrand (20) performed microscopic studies of the
germination of pollen upon the treated stigmas. They found that Bordeaux mixture 2-6-100, copper lime 20-80, and "Mike" sulphur reduced but did not
prevent growth of pollen upon the stigma, but Elgetol at 0.257o completely
prevented pollen germination on stigmas. Field trials indicated that
Elgetol inhibited fruit set seriously on apple trees and this material has
since been used extensively in fruit thinning. . Watson (31) designed an
experiment to study the specific effect of Elgetol sprays on the structure
of the pistil and upon subsequent pollen tube growth. He found no relation
between number and length of pollen tubes in pistils from treated and
untreated flowers, but the yield of fruit was reduced seriously when Elgetol was sprayed during blossom. He concluded that Elgetol destroyed the
receptive nature of the stigma, caused dehydration, browning, and death of
cells of the papillae. This is now considered to be the main mode by which
Elgetol acts as a chemical fruit thinner.
Schmidt (27) performed experiments in which he detected that certain
fungicides, especially thiuram and captan caused a reduction in the germin•
ation of apple, pear and plum pollen when sprayed into the open, blossom.
He found no reduction in yield in any treatment.
Rich (26) found that apple pollen would not germinate in sucrose
solution containing the fungicides: captan, glyodin, dichlone or ferbam while - 4 -
sulphur had a slight depressing effect. However, these fungicides had no serious effect on fruit set either when sprayed pollen was applied to unsprayed blossoms or unsprayed pollen was applied to sprayed blossoms.
The reciprocal experiment employed different varieties. He concluded that the method of immersing or suspending pollen grains in fungicide-sucrose solution was too severe to determine the safety of using fungicides at blossoming.
Eaton (8) also reported that captan sprays applied to apple anthers significantly reduced pollen germination and inhibited pollen tube elongation on sucrose-agar media, although not equally for all varieties.
Braun e_t al_ (2) studied the effect of several plant protection materials upon the germination of apple and pear pollen and found that pollen germination was inhibited by those plant protection materials which were contained in the sugar solution.
Braun et_ al_ (3) sprayed some apple varieties before and during flowering with the following chemicals: Orthocide 83 (0.15% captan),
Pomarsol forte (0.15%), Acricid (0.2%), Karathane (0.1%), Morestan (0.03%),
Fuklasin ultra (0.1%,) and Delan wettable powder (0.1%>) . He showed that spraying during flowering did not increase fruit drop. The germination capacity of the pollen was unaffected by preblossom spraying, but was often severely inhibited by spraying during flowering. No female flower parts were damaged. In a greenhouse trial the flowers were artificially pollinated with sprayed pollen and fruit set was greatly reduced.
Dhuria et al (6) investigated the influence of the insecticide thiodan on pollen germination and fruit set in apple. They found a significant reduction with the application of 0.2%, thiodan to the germination medium. - 5 -
Pollen germination and pollen 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 effect. The application of thiodan to open flowers caused only a slight reduction in pollen germination and the percentage of fruit set was not affected. The treatment of open anthers or stigmas did not significantly reduce pollen tube growth.
Kaspers (12) reported that sprays of 0.27o Orthocide 50 (captan) applied 3 or 4 times during blossoming to apple trees did not reduce fruit set.
Other species of tree-fruit were also examined by several investi• gators. Remy (25) worked with peach and plum pollen and found that nearly all of the test materials inhibited pollen germination more or less severely.
Eaton (7) working with sweet cherry pollen grains in vitro used a spraying technique instead of immersion of pollen grains in the dosage. He found that .sulphur did not reduce pollen germination but dichlone and ferbam reduced germination slightly. Captan almost entirely prevented pollen germination and arrested the elongation of pollen tubes.
Cristoferi e_t al (4) indicated that apricot pollen viability and fruit set were adversely affected by 0.27o ziram (807o a.i.) and particularly by
0.157= TMTD. Similar injurious effects on pears were recorded for the ziram spray and for 0.1% dodine (65% a.i.) but 0.2% zineb (80% a.i.) was harmless. In apple, zineb and dodine reduced pollen viability and fruit set, but ziram was not injurious unless applied at full anthesis in the laboratory and with controlled pollination in the field. There were no significant yield differences between treated and untreated trees of all
3 species under natural pollination. - 6 -
Gartel (10) reported that germination of grape pollen was inhibited when several plant protectants were applied over the germination media.
Shawa e_t al (28) 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 inhibited cranberry pollen germination.
Pollen collected from the sprayed flowers germinated from 40.87o-97.07o on
untreated sugar-agar media, while that from untreated flowers germinated
1007o. He also carried out field trials with fungicide sprays during the
blossoming period and cranberry yield was significantly reduced.
Lockhart (15) has shown that lowbush blueberry pollen had little or
no germination on artificial media (5?D agar and 13.57o sucrose) which con•
tained ziram or ferbam. Moderate germination occured on media that
contained zineb. Pollen grains from dusted plants germinated as well as
the control. Lockhart concluded that the pollen grains were enclosed
in the anthers at time of dusting, and the dust probably did not come in
contact with the pollen. He also found that the seed count from fungicide
trial plots showed that the number of seeds in plots treated with fungicides
was not significantly different from that in control plots.
B. Seed count in strawberry
Seed counts have been used by many investigators to indicate the
berry development of strawberry. Nitsch (22) demonstrated that the growth
of the receptacle was entirely dependent upon the presence of fertilized
achenes and obtained evidence that this was mediated through a mechanism
involving auxin-like growth substances. Tukey (29) also observed that
there was a direct relationship between the number of achenes present on the fruit and the size of that fruit at maturity. The largest fruits at maturity possessed the largest number of functional achenes, while smaller fruits had a progressively smaller number of achenes. He indicated that a small number of achenes may stimulate proportionally more development of the receptacle in milligrams per achene than would a large number.
Moore (21) indicated that the seed number and berry weight in the strawberry were not so closely associated as in the blueberry under con• ditions of poor fertilization. In the strawberry, each seed either con• tributes more hormone for receptacle growth or the hormone is utilized more efficiently than under conditions of relatively full seed set. In either case each seed is responsible for a greater amount of actual fruit weight when seed set is low.
C. The control of strawberry fruit rot
Grey mold of strawberries caused by Botrytis cinerea (Pers.) Fr. is the most important fruit rot of strawberries in many growing areas. In
Pacific coast fields, as elsewhere, losses are most serious when rainfall is excessive during the harvest period (23). In the current control program, it is recommended that strawberries should be sprayed or dusted with captan at least 3 times, starting when the first blossoms emerge (29, 22).
Freeman (9) working with the Siletz strawberry variety found that the fungicides folpet, captan, and thiram proved the most effective materials for controlling grey mold. Fruit size was affected by treatments, the trend being for fruit to be larger from plots treated with the more efficient fungicides. Powell (24) also noted that strawberry plants had benefited nutritionally from captan and that fruit size was increased. - 8 -
Gourley (11) indicated that the beneficial effect of disease control by a fungicide must be greater than any reduction in yield due to phtotoxicity.
There are no reports of effects of captan on strawberry pollen germination or fruit set. In other crops although captan may reduce pollen germination there may or may not be effects on fruit set. Reasons for this are not clear. Further research may help explain the apparent contradic• tions among the studies summarized here. - 9 -
MATERIALS AND METHODS
Two commercial varieties, Siletz and Northwest, were used in the experiments. Stock plants were grown in the field in July to propagate the runner plants. Digging of plants started in the middle of November and uniform runner plants were brought into a. heated greenhouse.
The plants were set into 18-cm pots and the varieties were separately put on two benches under supplementary illumination providing 16-hour daily photoperiods. After 25 days, the flowers started opening. All flowers were marked with a dated tag on the day that they opened, treated in accordance with the experiment being done and left until the fruit started
to turn pink. Fruits 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 total achenes, percentage of sound achenes per berry and berry weight per sound achene were recorded or calculated for each berry separately.
Pollen for germination tests was collected from the material grown in
the greenhouse. No pollen storage was used for any of the pollen germination
tests. .
The fungicide used in these experiments was captan 507o wettable powder
(N-(trichloromethylmercapto)-4-cyclohexene-l,2-dicarboximide) . The con•
centrations of captan used in each experiment were expressed as ppm active
ingredient.
Seed count study
Samples of 10 secondary hand-pollinated berries from the greenhouse were - 10 -
taken for estimations of achene viability in each berry. Berry weight was obtained and number of apparently sound and abortive achenes counted.
Water was added and the samples were disintegrated in a blender; the achenes that floated were separated from those that sank and the two groups dried separately and then counted. Counts were made of the floating and sinking achenes from each berry. Germination tests were done on both groups for each sample in petri-dish moist-chambers.
Statistical analyses
Analysis of variance was carried out on the number of days required to ripen, berry weight, number of sound achenes, number of abortive achenes, number of total achenes, percentage of sound achenes per berry and berry weight per sound achene. Duncan's New Multiple Range Test as described by
Li (14) was used to test differences among means. Covariance analysis was used to study the correlation between number of sound achenes and berry weight.
A. Pollen germination tests
1. Pollen germination with captan in the media
Pollen was collected from newly opened flowers of the varieties
Northwest and Siletz, and dried in the laboratory overnight. The pollen
grains were cultured on sucrose-agar media (107o sucrose and 0.757o agar) con• taining captan in concentrations of 0, 250, 500, 1000 ppm. ' The media were flowed into double-depression glass slides. Each slide was placed on wet filter paper in a petri-dish as a moist-chamber and kept at room temperature o (22 C). Counting was done after 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 0.757o 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 filter paper in a petri-dish as a moist-chamber.
After one hour pollen incubation, the different concentrations of captan at 0, 500, 1000, 2000 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 in the wells of double-depression slides.
Counting was done after 3 hours incubation in petri-dish moist- chambers at a room temperature of 22°C. The percent pollen germination was recorded by counting 100 grains in each depression.
The experimental design was a 2 x 5 factorial in a completely rando• mized design with two varieties, Northwest and Siletz, the 5 treatments, and the 2 petri-dishes as replicates within each treatment. Each depression represented a duplicate determination within each replicate.
4. Pollen germination with captan sprayed on dehisced anthers
Captan concentrations of 0, 500, 1000 and 2000 ppm in tap water were sprayed on open flowers after the anthers had dehisced. There was also an unsprayed,control. The following morning, the flowers; were . collected and the anthers taken off and allowed to dry in the laboratory for 2 hours.
Pollen grains from treated and untreated flowers were placed on 0.75%, agar media containing 10%, sucrose in the wells of double-depression slides.
Counting was done after 3 and 24 hours incubation in petri-dish moist- chambers at a room temperature of 21-22°C. The germination percentage was recorded by counting 100 grains in each depression.
The experiment was arranged as a completely randomized split-plot with the times of counting as the sub-plots. The main plots were Northwest and Siletz and the 5 treatments. The two petri-dishes were replicates within each treatment while depression counts represented duplicate determin• ations within each replicate. - 13 -
B. Greenhouse experiments
1. Berry set with captan.sprayed on flowers before anther dehiscence
Four different concentrations of captan at 0, 250, 500, 1000 ppm were applied on the tagged primary flowers in which anthers were mostly un• dehisced. After 3 hours when the sprays had dried, self-pollination was done by hand with pollen grains from the same treated flowers. No spray was applied to the control flowers and they only received hand pollination with untreated pollen. The results were analysed by the analysis of variance for a randomized complete block design which included 5 treatments.
Each block consisted of 5 pots in which flowers could be found at a uniform stage of development. There were 5 blocks of Siletz and 3 blocks of
Northwest. The data for the two varieties were analysed separately.
2. Berry set with captan sprayed on flowers after anther dehiscence
Captan concentrations of 0, 500, 1000 and 2000 ppm were applied to
the two secondary flowers from one cluster in each plant using an atomizer.
Most of the anthers in these flowers were dehisced. The following morning,
self-pollination was done by hand with pollen grains from the same treated
flowers. The control was hand pollinated with pollen from untreated flowers.
The experiment was a variation of the split-plot design with systematic
arrangement of varieties as whole plots. Each variety had 10 blocks, and
the 5 treatments were sub-plots. There were 2 flowers within each treat• ment and variety.
3. Comparison of spraying pistils versus anthers
Two secondary flowers from one cluster in each plant of the variety
Northwest were emasculated one day before opening. To treat pistils only,
one of the emasculated flowers was sprayed with 1000 ppm of captan and after - 14 -
the spray dried, pollinated with unsprayed pollen grains. To treat anthers only, the other flower was not sprayed with captan but was pollinated with pollen grains collected 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 pistils and sprayed anthers as 2 treatments.
4. Berry set in pistils sprayed at intervals after pollination
One secondary flower in each plant was used for this experiment. The
flowers were emasculated one day before opening and the pollen was applied one day after emasculation. Captan at 1000 ppm was applied at time of pollination or 2, 4, or 6 days after pollination.
The design was a variation of the split-plot with systematic arrangement of varieties Northwest and Siletz as whole plots (13). There were 7 blocks of each variety. The 4 times of spraying were the sub-plots.
5. Berry set in pistils pollinated at intervals after, spraying
The pair of secondary flowers from one cluster in each plant were
emasculated one day before opening. One flower of the pair was sprayed with
1000 ppm of captan one day after emasculation (corresponding to anthesis) and
the other flower was not sprayed. Both emasculated flowers were hand-
pollinated with untreated pollen grains. The four pollination times were
at anthesis, or 2, 4, or 6 days later.
The experiment was a variation of the split-split-plot with systematic
arrangement of varieties Northwest and Siletz as whole plots (13). There were 7 blocks of each variety. The 4 pollen applications times were the
sub-plots and sprayed and unsprayed pistils as the sub-units. - 15 -
RESULTS
Seed count study
In preliminary trials, separating achenes by visual methods and by flotation gave similar results. The percentage of germination of sinking achenes ranged between 60 and 100 per cent in all the samples, while the floating achenes did not germinate. Floating achenes were therefore described as abortive non-viable, and sinking achenes as sound and potentially viable.
The visual method for counting achenes was therefore used in all greenhouse experiments.
The total achenes per berry was the sum of the number of abortive and sound achenes.
A. Pollen germination tests
1. Pollen germination with captan in the media
No germination was obtained in any of media containing captan at 250,
500, 1000 ppm after either 3 or 24 hours incubation. The mean germination
percentage in the control after 3 hours incubation was 39?0 for Siletz and
417o for Northwest. After 24 hours, in control media the germination per• centage was increased to 457o in Siletz and 477o in Northwest. No analysis of variance was carried out on these data because there was no pollen germination in the media containing different captan concentrations.
2. Pollen germination with captan on the media
The sprays were applied to the media after one hour pollen incubation and the percentage pollen germination and the pollen 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. Pollen germination as affected by captan sprayed on the media
Treatment Mean percent pollen Mean pollen 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 in the same column sharing the same letter did not differ sig• nificantly 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 signifi• cantly reduced by both'500 ppm and 2000 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,, 427c and 3870 respectively) . The highest germination was found from water sprayed flowers. There was no significant difference in either variety between pollen from unsprayed and from 1000 ppm captan sprayed flowers.
As for the variety Siletz, only the 2000 ppm'concentration signific• antly reduced germination. There were no significant differences among the other treatments. - 19 -
Table 2. Pollen germination as affected by captan sprayed on undehisced
anthers.^
Treatment Northwest Siletz 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 letter did not differ significantly according to Duncan's New Multiple 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 (12%) 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. Pollen germination as affected 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
Siletz 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 in the same column sharing the same letter did not differ sig• nificantly according to Duncan's New Multiple 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 in Northwest and 5 blocks in Siletz, the data were analyzed separately
for each variety (Table 4).
No malformation of fruits was found in either variety. In the variety Northwest, the results showed no significant treatment effects.
In the variety Siletz, no significant effects 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 significantly decreased berry weight, sound achenes and total achenes per berry in comparison with the controls. No significant differences were found among the
3 captan concentrations and water. Water was not significantly different
from captan sprayed at 500 or 1000 ppm in its .effect upon the percentage of sound achenes per berry, and water gave a significant decrease in
comparison with either control or the 250 ppm spray. The water spray
in Siletz resulted in significantly greater berry weight per sound achene
than did any other treatment. Table 4. Berry set as affected by captan sprays before anther dehiscence
2 Variety Unsprayed Water Captan Captan Captan F •- - Standard sprayed 250 ppm 500 ppm 1000 ppm probability error sprayed sprayed sprayed
Days required Northwest 20 a 19 a 20 a 21 a 21 a 0.6 0.7113 to ripen Siletz 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) Siletz 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 Siletz 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 Siletz 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 Siletz 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 Siletz 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 Siletz 55 . c 181 a 95 be 118 b 105 be 15 0.0005 achene (mg) Means in the same row sharing the same letter did not differ significantly according to Duncan's New Multiple Test Range (p=.05) There were 8 degrees of freedom for error in Northwest and 16 in Siletz - 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 after anther dehiscence
Unsprayed Water Captan Captan Captan Standard sprayed 500 ppm 1000 ppm 2000 ppm error probability sprayed sprayed sprayed
Days required to ripen 26 a 27 a 27 a 27 a 26 a 0.3 0.4077
Weight per berry (g) 5.0 a 4.4a 2.8 b 2.6 b 1.5 c 0.3 0.0000
Number of sound achenes 96 a 84 a 40 b 32 b 14 c 5.9 0.0000
Number of abortive achenes 52 a 56 a 55 a 65 a 33 b 6.2 0.0095
Total number of achenes 148 a 140 a 95 b 98 b 47 c 10.2 0.0000
Percentage of sound achenes - Northwest 60 ab 52 be 41 cd 25 e 29 de 4.6 0.0054 Siletz 68 a 65 ab 24 c 32 de 18 e 4.6 0.0054
Berry weight per sound achene (Mg) 53 b 57 ab 84 ab 86 a 87 a 10.4 0.0458
Means in the same row sharing the same letter did not differ significantly according to Duncan's New Multiple Test Range (p=.05)
There were 72 degrees of freedom for error - 26 -
3. Comparison of spraying pistils versus anthers
Either pistils or anthers were sprayed with captan. Pistils . 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 pistils 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 pistils 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 pistils or anthers with captan
Sprayed Sprayed Standard anthers pistils error probability
Days required to ripen 24 24 0.3 0.8594
Weight per berry (g) 3.3 4.4 0.3 0.0121
Number of sound achenes per berry 35 79 4.9 0.0000
Number of abortive ro achenes per berry 100 89 4.7 0.0934
Total number of achenes per berry 135 167 7.5 0.0065
Percentage of sound achenes per berry 25 47 2.2 0.0000
Berry weight per sound achene (mg) 101 59 5.2 0.0000
There were 17 degrees of freedom for error - 28 -
4. Berry set in pistils sprayed at intervals after pollination
After pollination, there was no significant effect of time of spraying upon the number of days required to ripen or the number of total achenes per berry (Table 7). When pistils were sprayed with captan immediately after pollination, mean weight per berry, mean number of sound achenes per berry and mean percentage of sound achenes per berry were significantly reduced. The same treatments however significantly increased the mean number of abortive achenes per berry and mean berry weight per achene.
Delays of 2, 4, or 6 days in applying the spray gave similar results 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 significant correlation (r=0.83) between the number of sound achenes and berry weight. Table 7. Berry set with captan sprays at intervals after pollination
Spraying days after pollination Standard F 0 2 4 6 error probability
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
Total 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 in the -same row sharing the same letter did not differ significantly according to Duncan's New Multiple Range Test (p=.05)
There were 36 degrees of freedom for error - 30 -
5. Berry set in pistils pollinated at intervals after spraying
Where pistils 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 pistils 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 all fruit 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 polli• 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 pistils than in unsprayed pistils 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. Effects upon berry set of pollination at intervals after spraying
Variety Pollination days after spraying Standard F 0 2 4 6 error probability
Days required to Northwest 25 a 26 a 26 a 26 a 0.4 0.3464 ripen Siletz 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) Siletz ' 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 Siletz 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 Siletz 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 Siletz 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 Siletz 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) Siletz 69 a 75 a 11 b 7 b 11.6 0.0290
Means in the same row sharing the same letter did not differ significantly 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 pistils 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 al
(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 all 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
its 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
full anthesis. Lockhart (15) and Dhuria e_t al (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 at the time of spraying.
B. Greenhouse experiments
Days required to ripen
There was no significant effect of captan sprays upon the period
from flower opening to berry maturity. Variations in number of days for
berry ripening were found among various experiments when plants were grown
in the greenhouse. This might be due to different temperatures during
the several growing periods.
Berry weight and number of achenes
There was a highly significant correlation between berry weight and
number of sound achenes in each greenhouse experiment. The development
of the strawberry receptacle was influenced by the number of sound achenes
per berry as well 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 effect involving auxin•
like growth substances as described by Nitsch (22) , and Tukey (29) and
Moore (21). . Way (32) has recently articulated the generally accepted
view that adequate pollination and fertilization are required for normal
fruit development. Darrow (5) also indicated that pollination of all
pistils of the strawberry flower was necessary for maxium berry size.
1. Berry set with captan sprayed before anther dehiscence
The anther tissue of the Northwest variety 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 Siletz
variety appeared to slightly absorb the captan since the berry weight - 36 -
and achene set were reduced by captan sprays. Earlier reports implied
that pollen germination was unaffected by captan when sprayed on the un• dehisced anthers. The results 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 after anther dehiscence
Captan sprays applied to the flowers after anther dehiscence sig• nificantly reduced berry weight and achene set. Serious reduction of berry development caused fruit malformations. These results support
those of Bennett (1) who observed that the proportion of misshapen fruits was increased when fungicide sprays were applied to strawberry flowers of Sovereign variety, but Talisman variety was little affected. Pollen
germination tests also showed that captan reduced pollen germination when captan was sprayed on the dehisced anther (Table 3). Schmidt (27) with pear, plum and apple, Rich (26) with apple, Braun et al (3) with apple and Kaspers (12) with apple found no significant effect on fruit
set when captan was sprayed into the open blossom under orchard conditions,
but Shawa et: al_ (28) found that cranberry yield was significantly reduced when captan was sprayed during the blossoming period in the field.
3. Berry set with captan sprayed on pistils or anthers
Berry set was greatly reduced when emasculated flowers were artificially
pollinated with pollen from sprayed anthers as compared with sprayed
pistils and artificially pollinated with unsprayed pollen (Table 6).
These results support those of Braun e_t al_ (3) who reported that no female
apple flower parts were damaged by captan, but in greenhouse trials, when
the flowers were artificially pollinated with sprayed pollen, fruit 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 fruit set when either pistils or anthers were sprayed with captan.
4. Berry set in pistils 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 fertilization 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 fruit probably was due to some of the pollen grains
lodged between the papillae of the stigma and escaping the fungicide.
5. Berry set in pistils pollinated at intervals after spraying
Where pistils were pollinated at anthesis and sprayed with captan
the berry weight and achene set were significantly reduced as compared with
pistils 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 pistils as shown by fruit set since
either pistils sprayed or not sprayed with captan could remain recptive
up to 2 days after anthesis in the greenhouse. That strawberry pistils - 38 -
may remain receptive for several days in the field was shown by Moore
(21). He found that strawberry pistil receptivity was greatly reduced after 168 hours under warm conditions, but cool temperatures tended to
slow down the physiological ageing of the pistils 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 if not pollinated.
Berry weight and achene set were reduced in greenhouse trials by
captan as reported here. It would seem that under specific circumstances
berry set could be reduced in the field. This probably would not always
occur and would be difficult to demonstrate as captan did not injure
pistils or their receptivity and pistils can remain receptive for several
days in the field. While captan could affect pollen germination during
spraying, bees probably could get sufficient unsprayed pollen from later
opening flowers to allow fruit 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 fruit 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. al. 1966. The effects of fungicidal treatment
during flowering on some fruit 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 fruit 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.
Mitl. Biol. Bundesanst., Berlin Dahlem, H. 104, 108-112.
11. Gourley, C. 0. 1968. Fungicidal control of Botrytis cinerea on
four strawberry varieties. Can. J. Plant Sci. 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. Field plot
technique. Burgess Publishing Company. Minneapolis, Minnesota,
p..194-95.
14. Li, J. CR. 1964. Statistical Inference. Vol.1. Edwards Brothers
Inc. Ann Arbor, Michigan p.270-73.
15. Lockhart, C. L. 1967. Effect of fungicides on germination of
lowbush blueberry pollen and on number of seeds per berry. Can.Plant
Pis. Surv. 47, 72-3.
16. MacDaniels, L.H., and Furr, J. R. 1930. The effects of dusting
sulphur upon the germination of the pollen set of fruit of the apple.
N. Y. (Cornell) Agric. Exp. Sta. Bull. No. 499.
17. MacDaniels, L. H., and Burrell, A. B. 1934. The effect of sulphur
fungicides applied during the bloom, on the set of apple fruits.
Phytopath. 24, 144-50.
18. MacDaniels, L. H., and Hildebrand, E. M. 1938. Results of further
studies on the effect of bactericides on pollen germination and fruit
set. Proc. Amer. Soc. Hort. Sci. 35, 14-23.
19. MacDaniels, L. H., and Hildebrand, E. M. 1938. The effect of copper
compounds applied to spur units during bloom upon the set of apple
fruits. Proc. Amer. Soc. Hort. Sci. 36, 230-33. - 41 -
20. MacDaniels, L. H., and Hildebrand, E.M. 1940. A study of pollen
germination upon the stigmas of apple flowers treated with fungicides.
Proc. Amer. Soc. Hort. Sci. 37, 137-40.
21. Moore, J. N. 1964. Duration of receptivity to pollination of
flowers of the high bush blueberry and the cultivated strawberry.
Proc. Amer. Soc. Hort. Sci. 85, 295-301.
22. Nitsch, J.P. 1950. Growth and morphogenesis of the strawberry as
related to auxin. Amer. J. Bot. 37, 211-15.
23. Powelson, R. L. 1960. Initiation of strawberry fruit rot caused
by Botrytis cinerea. Phytopath. 50, 491-94.
24. Powell, D. 1954. The effect of captan on gray mold rot incidence
and yield of strawberry. Plant Pis. Rep. 38, 209-11.
25. Remy, P. 1953. Contribution a l'etude du pollen des arbres fruitiers
a noyau, genre prunus. Ann. Inst. Nat. Recherche agron. Serie B.
Ann. Amelioration des Plantes. 3_, 351-378.
26. Rich, A. S. 1957. Effect of various fungicides applied during
bloom on apple pollination and fruit set. Agr. Chem. 12(6)T 64-6.
27. Schmidt, T. 1956. Untersuchungen liber die Beeinflussung der
Pollenkeimung durch Spritzung in die BlUte und ihre Auswirkung in
der Praxis. Pflsch. Ber. Wien. 16, 75-9.
28. Shawa, A. Y., Doughty, C. C., and Johnson, F. 1966. Effect of
fungicides on McFarlin cranberry pollen germination and fruit set.
Proc. Amer. Soc. Hort. Sci. 89, 255-58.
29. Tukey, R. B. 1952. Some phsiological factors influencing the growth
and development of strawberry fruits. 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. Effect of Elgetol sprays on pistils of apple
flowers. . Proc. Amer. Soc. Hort. Sci. 60, 151-54.
32. Way, D..W. 1968. Strawberry fruit malformation. I. Pomological
aspects. Ann. Rept. East Mailing Res. Sta. for 1967. 199-203. 5
- 43 -
APPENDIX - 44 -
Table 10. ~F-probabilities from the analysis of variance for pollen
germination as affected by captan sprayed on the media
Source of Degrees of Levels of statistical significance variance freedom percent pollen Length of pollen germination tube Q>)
Variety (v-1) 1 0.2473 0.3041
Treatment (t-1) 4 0.0000 0.0082
Variety x treatment (v-l)(t-l) 0.3238 Replicates within varieties and treatments 10 vt(r-l) 0.0186 Wells within replicates, varieties and treatments vtr (w-1) 20
Total vtrw-1 39 - 45 -
Table 11. F-probabilities from the analysis of variance for pollen germination as affected by captan sprayed on the undehisced anthers
Source of Degrees of Levels of statistical variance freedom significance
Variety (v-1) 1 0.6415
Treatment (t-1) 4 0.0001
Variety x treatment (v-l)(t-l) 4 0.0037
Replicates within varieties and treatments vt(r-l) 10 0.1271
Wells within replicates, varieties and treatments vtr (w-1) 20
Total vtrw-1 39 - 46 -
Table 12. F-probability from the analysis of variance for pollen germination as affected by captan sprayed on the dehisced anthers
Source of Degrees Levels o.f Variance of statistical freedom significance
Variety (v-1) 1 0.0175
Treatment (t-1) 4 0.0007
Variety x treatment (v-1) (t-1) 4 0.1065
Replicates within varieties and treatments vt(r-l) 10 0.2196
Wells within replicates, varieties and treatments vtr (w-1) 20 0.0005
Incubation (i-l) 1 0.0038
Incubation x variety (i-l)(v-1) 1 0.5392
Incubation x treatment (i-l) (t-1) 4 0.0497
Incubation x variety x treatment (i-l)(v-1)(t-1) 4 0.2641
Incubation x replicates within varieties and treatments vt(i-l)(r-l) 10 0.4963
Error vtr(i-i)(w-1) 20
Total vtrwi-1 79 Table 13. F-probabilities from the analysis of variance for berry set as affected by captan sprays before anther dehiscence
Levels of statistical 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 Northwest per berry per berry (mg)
Block (b-1) 2 0.7946 0.035 0.5563 0.8402 0.1636 0.9270 0.3769
Treatment (t-1) 4 0.7113 0.2655 0.1384 0.4953 0.3403 0.2176 0.3424
Error (b-1) (t-1) 8
Total bv-1 14
Siletz Block (b-1) 4 0.6245 0.4310 0.5439 0.0752 0.4617 0.0391 0.0759
Treatment (t-1) 4 0.2086 0.0300 0.0000 0.1133 0.0156 0.0000 0.0005
Error (b-1)(t-1) 16
Total bv-1 24 Table 14. F-probabilities from the analysis of variance for berry set as affected by captan sprays after anther dehiscence
Levels of statistical 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) 19 0.0000 0.0000 0.0000 0.0000 0.0000 0.0691. 0.0742
Treatment (t-1) 4 0.4077 0.0000 0.0000 0.0095 0.0000 0.0000 0.0458
Variety x treatment (v-1)(t-1) 4 0.0808 0.2515 0.1690 0.7839 0.3467 0.0054 0.0143
Experimental error v(t-l)(b-1) 72 0.0000 0.0000 0.0000 0.0000 0.0000 0.2909 0.1143
Fruits/ error tbv(f-l) 100
Total bvtf-1 199
Since the main plots (varieties) were in rows, inferences were restricted to treatments and the variety x treatment interaction (13) Table 15. F-probabilities from the analysis of variance for berry set after spraying either pistils or anthers
Levels of statistical 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)
Block (b-1) .17 0.2484 0.3239 .0.4377 0.0131 0.0914 0.3412 0.0883
Treatment (t-1) 1 0.8594 0.0121 0.0000 0.0934 0.0065 0.0000 0.0000
Error (b-1)(t-1) 17
Total bt-1 35 Table 16. F-probabilities from the analysis of variance for berry set when pistils were sprayed at intervals after pollination
Levels of statistical 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 13 0.0071 0.0315 0.0553 0.1637 0.3707 0.0173 0.5608
Treatment (t-1) 3 0.7759 0.0036 0.0000 0.0006 0.1806 0.0101 0.0000
Variety x treatment (v-1)(t-1) 3 0.2647 0.5225 0.1327 0.1683 0.0697 0.0376 0.1276
Error v(b-l)(t-1) 36
Total vtb-1 55
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 pistils pollinated at intervals after anthesis
Levels of statistical 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 bf sound per sound to ripen berry achenes berry achenes achene per berry per berry (mg)
Whole plot bv-1 13 0.000,0 0.0024 0.0538 0.3635 0.2057 0.0119 0.0000
Pollination (p-1) 3 0.0014 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Variety x pollination (v-l)(p-l) 3 0.3464 0.0026 0.0206 0.0030 0.0007 0.0015 0.0290
Experimental error v(b-l)(p-1) 36 0.0266 0.0273 0.0063 0.1288 0.0616 0.0838 0.0138
Captan (c-1) 1 0.1015 0.0004 0.0000 0.5337 0.0034 0.0000 0.0221
Variety x captan (c-1)(v-1) 1 0.9505 0.2187 0.8065 0.0745 0.2506 0.3958 0.2293
Pollination x captan (p-1)(c-1) 3 0.4464 0.1281 0.0000 0.0000 0.5307 0.0000 0.0000
Variety x pollination (v-1)(p-1) x captan (°-l) 3 0.5633 0.4515 0.7348 0.6705 0.6837 0.7742 0.8221 Error vp(b-l)(c-1) 48 To tal bvps-1 111 Since the main plots (varieties) were in rows, inferences were restricted to treatments and the variety x treat• ment interaction (13)