Relationship between origin and genetic diversity in Chinese soybean germplasm

The soybean [Glycine mar (L.) Merr.] was domesticated in China. Information about the amount and distribution of genetic diversity in China is critical to effective soybean germplasm management. Information is currently available from only a few provinces in China. The objectives of this research are to estimate the genetic variation within and among four geographically diverse provinces (Zhejiang, Sichuan, Gansu, and Hebei) in China and to determine the relationship between geographical origin and genetic diversity. Ten primitive cultivars from each province were characterized by random amplified polymorphic DNA (RAPD) fragments produced from 31 selected decamer primers. CNS, an important U.S. ancestral line, was also included as a control. Genetic variation was estimated by AMOVA analysis with 125 polymorphic RAPD fragments. Genetic distances were calculated by means of Jaccard's coefficient and expressed as dissimilarity coefficients. Unweighted paired group method using arithmetic averages (UPGMA), Ward's minimum-variance method, VARCLUS, and multidimensional scaling (MDS) were applied to define the genetic relationships. AMOVA identified significant genetic differences between all pairs of provinces except between Zhejiang and Sichuan. The greatest difference was observed between Hebei and Zhejiang. There was disagreement among the clustering methods, but each procedure identified clusters of accessions that originated from the same province. Based on data from all clustering procedures, six major clusters containing a total of 32 accessions were defined with each cluster dominated by accessions from a single province. These data provide additional evidence that primitive cultivars of China were generally genetically isolated in relatively small geographical areas.