The genetic diversity of cultivated soybean grown in China

Cultivated soybean (Glycine max) is an economically important crop that is grown for its oil and protein products. A better knowledge of its genetic diversity will be valuable for the utilization, conservation, and management of germplasm collections. Using the database of the National Germplasm Evaluation Program of China (NGEPC), we studied the geographical distribution of accessions, the genetic diversity of 15 qualitative and quantitative characters, and the genetic diversity centers of cultivated soybean in China using variation in these 15 traits and genetic diversity indexes (Shannon index). Cultivated soybean is widely distributed throughout China. As an indication of its distribution, a line can be roughly drawn from the Daxinganling mountains in northeastern China to the Qingzang plateaus in southwestern China based on the abundance of accessions and locations of the collections. Of the 22,637 known accessions in China, the 20,570 collected over a vast area between latitudes 18degrees and 53degreesN and longitudes 80degrees and 136degreesE were used in this study. The Shannon indexes of various morphological traits were calculated. Cultivated soybean accessions were found to exhibit a higher genetic diversity in the area between 34degrees-41degreesN and 110degrees-115degreesE. On the basis of the geographical distribution of a number of accessions, and their genetic diversity, one genetic diversity center-downstream of the Yellow River Valley-is proposed. Based on these results and on Vavilov's theory on crop origins, one possible diversity center was proposed.