On the genetics of self-incompatibility in sweet cherry: Identification of S-genotypes; genetical and physiological effects on self-fertility and breakdown of self-incompatibility

A total of 20 pollen incompatibility groups in sweet cherry were identified among 54 cultivars, selections and seedlings by using PCR based S-allele typing and controlled pollination tests. Three novel S-alleles (Sz, Sy and S?) were newly identified and these extended to a total of nine the S-alleles current reported. Five new S-genotypes combinations, which were known to be possible combinations based on previously known six S-alleles (S1 through S6), were positively identified from five seedling populations resulting from half homologous crosses. Some cultivars which belong to pollen incompatibility groups with previously unidentified S-genotypes were characterized as to their S-genotypes.; It was proven by a 1/2 diallele cross and PCR based S-allele typing analysis that there is no "Universal pollinizer group" which had previously been designated as "Group O".; A total of seven self-fertile sweet cherry cultivars/selections were used in testing the hypothesis that fully compatible pollination would increase fruit set compared to self pollination in self-fertile sweet cherries.; In order to test this hypothesis, the S-genotypes of all subjected cultivars/selections were determined based on the results of controlled pollination tests after emasculation and PCR based S-allele typing analysis. The higher fruit set of self-fertile cultivars/selections due to open pollination indicated that the additional pollen donor was probably advantageous for fruit set in self-fertiles in my preliminary field study. However, no statistically significant differences were found between fully and half (self) compatible pollination in the caged trees in subsequent years' studies.; Physiological breakdown of self-incompatibility in sweet cherry was studied. This sweet cherry research reports results of experiments with the exception to the rule in self-incompatibility systems in higher plants, i.e. when self-incompatible genotypes actually set self seed(s) and/or seed from genetically incompatible genotypes.; Within the same S-genotype combination, there were no significant difference that depended on cultivars, in either fruit set or pollen tube growth measurements. This suggested that other genes not linked to the S-locus had no effect on breakdown of self-incompatibility. Among the S-genotypes, the highest breakdown rate was shown in S3S4. The percentage of breakdown ranged from 0--25% in incompatible pollinations; of all S-genotype combinations, when temperatures were increased from 10°C to 25°C.