Inheritance of seed shattering in interspecific hybrids between Fagopyrum esculentum and F. homotropicum

Fagopyrum esculentum Moench, common buckwheat (2n = 2x = 16), is a sporophytic self-incompatible species with dimorphic flowers, which is resistant to seed shattering, a trait often lost in interspecific crosses. The objective of this study was to determine the inheritance of seed shattering in interspecific crosses with the shattering species F. homotropicum Ohnishi [=F. esculentum var. homotropicum (Ohnishi) Q-F. Chen] (2n = 2x = 16) to use this species in buckwheat improvement. Four interspecific crosses between F. homotropicum and F. esculentum were made by means of ovule culture. Eight F2 populations derived from F1 single plants were developed and 28 F3 lines from F2 shattering plants were used for progeny testing. The F1 interspecific hybrids expressed seed shattering, indicating that shattering is dominant to nonshattering. The F2 populations from individual F1 plants segregated in the ratios of 3:1, 9:7, and 27:37, supporting the control of shattering by three complementary dominant genes, the first report of multiple gene control in buckwheat. The F3 progeny testing confirmed the F2 segregation patterns. The different segregation ratios in the F2 populations may have been caused by heterogeneity of F. esculentum because of cross-pollination. The proposed genetic model describes the genotype of F. homotropicum as homozygous dominant to explain the absence of nonshattering genotypes. Fagopyrum esculentum genotypes are homozygous recessive at a minimum of one locus to explain the absence of shattering genotypes. This model provides an explanation for the occurrence of shattering phenotypes from crosses between two nonshattering parents and nonshattering phenotype from crosses between, or selfing of, shattering plants.