Genetic Base of 651 Chinese Soybean Cultivars Released during 1923 to 1995

A diverse genetic base is important to breeding progress. The genetic base of U.S. and Canadian (US-CAN) soybean [Glycine max (L.) Merr.] cultivars is narrow. Modern Chinese soybean cultivars have been cited as a reservoir of genetic diversity for U.S. breeding. However, the genetic base of Chinese soybean cultivars is not well characterized. The purpose of this paper was to quantify the genetic base of Chinese soybean breeding by means of coefficient of parentage (CP) analysis and to compare it with that of US-CAN soybean. Three hundred thirty-nine ancestors were identified in the pedigrees of 651 Chinese soybean cultivars released during 1923-1995. Ancestors originating from China contributed 88% of the genes to the Chinese genetic base, and 45 exotic ancestors contributed 12%, as determined by CP analysis, Comparison of Chinese and US-CAN bases showed that (i) the genetic base of Chinese soybean breeding was much larger than that ofthe US-CAN and (ii) the Chinese base has continued to expand with time while the US-CAN base has changed little. Analysis showed that 35 and 339 ancestors contributed 50 and 90% of the genes to Chinese soybean cultivars, while only five and 26 ancestors contributed similar amounts to the US-CAN base. The three major soybean growing regions in China, Northeastern (NEC), Northern (NC) and Southern (SC) had little soybean ancestry in common with each other and constituted almost independent genetic bases. Each of the major Chinese growing regions had more ancestors and a more uniform distribution of ancestral contributions than did the total US-CAN breeding effort. Although the genetic base of both Chinese and U.S. soybeans are dominated by Chinese landraces, no landraces were identified by name as common to both. In recent decades, 24 U.S. cultivars and lines have been bred to Chinese stock. These U.S. materials now constitute 7.3% of the genetic base for Chinese cultivars and have led to important yield advances in China. In contrast, U.S. breeding has made little use of Chinese cultivars. By virtue of their broad genetic base and isolation from U.S. cultivars, modern Chinese soybean cultivars are potentially important to U.S. breeding programs.