Genetic diversity among soybean accessions from three countries measured by RAPDs

Soybean [Glycine mar (L.) Merr.] was domesticated in China but has a long h istory of cultivation on the Korean peninsula and in Japan. All three areas are considered important sources of soybean germplasm. The objectives of t his study were to evaluate the genetic variation in soybean within and amon g China, S. Korea, and Japan by means of 120 accessions from eight Chinese and three S. Korean provinces, and three Japanese districts; and to relate genetic diversity patterns to geographical regions. Genetic relationships w ere estimated by 115 random amplified polymorphic DNA (RAPD) markers with s imple matching coefficients expressed as Euclidean distances. Hierarchical and nonhierarchical cluster analyses as well as principal component analysi s were used to define relationships among the genotypes. The results indica te that the mean genetic distance within China is much larger than that wit hin Japan or S. Korea, but smaller than that between China and Japan or S. Korea. Cluster and principal component analyses almost completely separated the accessions from China from those of Japan and S. Korea, but could not distinguish between the accessions from Japan and S. Korea. These results a re consistent with previous research using enzymes and morphological data t o classify soybean germplasm from Asia. The groups formed by cluster analys is were mainly based on the frequencies of RAPD fragments among accessions and generally reflected the geographical regions of origin. No clear relati onship was found between latitude and genetic diversity among accessions fr om these countries. Although the soybean accessions from Japan and S. Korea originally came from China, these data indicate that current accessions fr om Japan and S. Korea are genetically very distinct from those from China a nd more similar to each other.