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 coeffi cient of parentage (CP) analysis and to compare it with that of US-CAN soyb ean. Three hundred thirty-nine ancestors were identified in the pedigrees o f 651 Chinese soybean cultivars released during 1923-1995, Ancestors origin ating from China contributed 88% of the genes to the Chinese genetic base, and 45 exotic ancestors contributed 12%, as determined by CP analysis. Comp arison of Chinese and US-CAN bases showed that (i) the genetic base of Chin ese soybean breeding was much larger than that of the US-CAN and (ii) the C hinese base has continued to expand with time while the US-CAN base has cha nged little, Analysis showed that 35 and 339 ancestors contributed 50 and 9 0% of the genes to Chinese soybean cultivars, while only five and 26 ancest ors 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 a lmost independent genetic bases. Each of the major Chinese growing regions had more ancestors and a more uniform distribution of ancestral contributio ns 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 landr aces 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 n ow constitute 7.3% of the genetic base for Chinese cultivars and have led t o important yield advances in China. In contrast, U,S. breeding has made li ttle use of Chinese cultivars, By virtue of their broad genetic base and is olation from U.S, cultivars, modern Chinese soybean cultivars are potential ly important to U.S, breeding programs.