Use of Self-Compatibility and Modifier Genes for Breeding and Genetic Analysis in Common Buckwheat (Fagopyrum esculentum)

Common buckwheat plants have heteromorphic self-incompatibility. Using two self-fertilizing lines, we revealed that there are two distinct systems of self-compatibility, one using a self-compatible allele, Sh, the other using modifier genes located outside the S locus and suppressing the functions of the S-locus genes. Sh appears to have been produced by recombination in the S supergene (giSIPPA/giSIPPA), in which each gene is functional. The modifier genes control the intensity of self-incompatibility and have three distinctive features: (1) Pollen shows cross-compatibility with styles of all flower types, although the compatibility is influenced by the genetic background of those plants. (2) Flower morphology of F1 plants is controlled by the genotype of the S locus. (3) F1 plants show high self-compatibility, although the level of self-compatibility is influenced by genetic background. The use of these genes for buckwheat breeding is discussed.