Genetic differentiation in relation to seed weights in wild soybean species (Glycine soja Sieb. & Zucc.)

Seed weight is one of the most important botanical and phylogenetic characteristics. The study objective was to understand whether there is genetic difference in different seed weights of wild soybean (Glycine soja Sieb. & Zucc.). A total of 563 wild soybean samples, which belonged separately to genebank germplasm accessions (220 samples), one regional population samples (293 plants) and one natural population (150 plants), were analyzed using microsatellite markers. Of four size classes, the smallest seed size type had the highest coefficient of variation in seed weight; small and large seed types had relatively great genetic differences. In the national genebank germplasm accessions, genetic diversity gradually decreased from quantitatively dominant small and middling seed types to less frequent large seed types. In the regional and natural populations, generally, small to middling seed sizes had higher genetic diversity than the smallest and larger seed sizes. Cluster analysis revealed genetic differences in seed size traits. The semi-wild type (Glycine gracilis Skvortzow) was the most genetically differentiated from other seed sizes. However, it was also clearly shown that the phylogenic genetic differentiation among seed sizes was less than the genetic differentiation among geographical habitat populations in the wild soybean species.