Genetic differentiation between summer and autumn maturing cultivars of soybean (Glycine max (L) Merrill) in Kyushu district of Japan

135 soybean landraces and pure line selections from Kyushu district of Japan were assayed for isozyme and seed protein loci in order to determine the genetic structure of the groups of summer and autumn maturing cultivars. Out of the 16 tested loci, Dial, Enp, Estl, and Ti exhibited a marked difference in allelic frequency between both groups. The summer cultivar group had a high frequency for Dial-b, Enp-b, Estl-a and Ti-b, whereas Dial-a, Enp-a, Estl-b and Ti-a were predominant in the autumn group. The analysis of multi-locus genotypes revealed that both groups mostly consisted of different multi-locus genotypes. The allelic combination of Dial-b Enp-b Estl-a Ti-b was most frequently observed in the summer cultivars, whereas four genotypes, Dial-a Enp-a Estl-a Ti-a, Dial-a Enp-a Estl-b Ti-a, Dial-a Enp-b Estl-b Ti-a and Dial-a Enp-a Estl-b Ti-b, occupied most of the autumn cultivars. These results indicated that both groups were appreciably differentiated from each other. The summer cultivar group also included a few accessions having the multi-locus genotypes observed predominantly in the autumn group or Acol-b characteristic of the landraces native to northern Japan. It seems likely that the summer cultivar group was not phyletically derived from a single common ancestor, but partly involves the landraces with early maturity derived from northern Japan. Dial, Enp, Estl and Ti are useful genetic markers to trace the origin and dissemination paths of Japanese soybean landraces.