Inheritance of self-compatibility and flower morphology in an inter-specific buckwheat hybrid

Sun Hee Woo¹.,Taiji Adachi²., Seung Keun Jong³ and Clayton G. Campbell⁴

¹ Agriculture and Agri-Food Canada, Crop Diversification Centre, Morden, Manitoba, Canada R6M 1Y5; ² Applied Genetics and Biotechnology Division, Faculty of Agriculture, Miyazaki University, Gakuen Kibanadai Nishi 1-1, Miyazaki 889-2154, Japan; ³ Dept. of Agronomy, College of Agriculture, Chungbuk National University, Cheongju 360-763, Korea; ⁴ Kade Research Ltd. Morden, Manitoba., Canada R6M 1E9.

Woo, S.H., Adachi, T., Jong, S.K. and Campbell, C.G. 1999. Inheritance of self-incompatibility and flower morphology in an inter-specific buckwheat hybrid. Can. J. Plant Sci. 79: 483-490.

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 (F. 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 numbers, 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 which 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 S^h. These genes can be characterized by a relationship of dominance, i.e. S >S^h >s. The introgression of F. homotropicum genes into common buckwheat was verified by means of electrophoretic analysis of seed proteins.

Key words: interspecific crosses, buckwheat, Fagopyrum esculentum, flower morpholgy, self-compatibility