Genetic Variation of Local Varieties of Soybean in the Western Part of the Shikoku Mountains in Japan

Abstract

Fifty-four accessions of local soybean strains collected from villages in the western part of the Shikoku Mountains were examined to assess genetic variation using the RAPD method. The accessions included 25 yellow, 17 black, 2 brown and 10 green seed-coat strains. Sixty-eight out of 138 bands detected by 21 RAPD primers were polymorphic. The average genetic distance for all the pairwise combinations was 0.114 ± 0.0336, which indicates that the local strains retained more than 80% of the genetic variation of the Japanese landraces reported previously. The genetic distance within yellow strains, black strains (including two brown strains) and green strains was 0.114 ± 0.0273, 0.0969 ± 0.0333 and 0.0840 ± 0.0309, respectively. These values were significantly different from each other. The genetic distance between the strains in groups with different seed-coat colors was significantly different from zero. The coefficient of genetic differentiation, GST, among the seed-coat colors was 0.174, indicating a large genetic differentiation. The NJ tree revealed the presence of three clusters: two were mainly composed of yellow and black strains, respectively, and the other one consisted of a mixture of yellow, black and green strains. However, monophyly of the seed-coat color groups was not supported except for some small subgroups. These results suggest that repeated introduction of seeds from outside seed sources and/or frequent hybridization among the strains with different seed-coat colors within the region had occurred during the long history of soybean cultivation in the Shikoku Mountains.