Seong-Woo Cho

Inheritance of Self-Compatibility in a Buckwheat Hybrid

Abstract This study was conducted to determine the inheritance of self-compatibility and homomorphic flower type when the wild species Fagopyrum homotropicum was crossed with common buckwheat (Fagopyrum esculentum). Unidirectional interspecific hybrids between cultivated F. esculentum Moench. (common buckwheat) and its wild relative F. homotropicum were produced after controlled pollination and embryo rescue culture. Cross-compatibility was found to be better when thrum-type common buckwheat was used as the female parent rather than the pin-type. The resulting F1 plants were partially fertile, late maturing, and intermediate between the parents in flower shape and plant height. They segregated into heterostylic (thrum only) and homostylic types in equal number, indicating that homostyly is controlled by a single dominant gene. The thrum-type F1 hybrids were backcrossed to common buckwheat and the progenies were raised utilizing embryo rescue culture. The homostylic F1 hybrids were advanced to the F2 and F3 generations through self-fertilization and utilized, together with the BC1F1, for the analysis of the stylar genes. The results obtained indicate that the genes coding for heterostyly and homostyly are controlled by the multiple allelic gene S. It appears that the pin/thrum complex in F. esculentum is governed by a single genetic locus S with two alleles, S and s, that control the reaction in Ss (thrum-type) as well as the ss (pin-type) plants, respectively. The homomorphic flower type of F. homotropicum is governed by the allele Sh. These genes can be characterized by a relationship of dominance, i.e., S>Sh>s. The introgression of F. homotropicum genes into common buckwheat was verified by means of electrophoretic analysis of seed proteins.