Epistasis for quantitative traits in crosses between soybean lines from China and the United states
Epistasis has sometimes been reported in qualitative and quantitative traits of soybean [Glycine max (L.) Merr.]. Our objective was to determine the extent to which epistasis occurred in crosses between soybean lines adapted to similar latitudes in Liaoning, China, and in Ohio, USA. We crossed ‘Tiefeng #27’ x HS97-4534 and ‘Ohio FG1’ x ‘Shennong #6’, and developed random F4–derived lines from each cross and BC1F3–derived lines from the backcross to each parent. We tested the lines, along with parents and their checks, at Plain City, OH, in 2005 to 2007, and at Shenyang, Liaoning, in 2005 and 2006. Comparison of the means of parents, biparental lines, and both backcrosses revealed significant epistasis for plant height, maturity, 100-seed weight, yield, internode length, number of branches, harvest index, and content of protein and oil, but the epistasis was not expressed consistently across environments or parental combinations. Further, in some cases simple digenic epistasis did not account for the results, implying higher-order interactions among loci. Some of the results could be explained by interactions of loci controlling timing of reproductive stages and interactions between such loci and the environment. Breeders who make crosses between soybean lines adapted to northeastern China and the midwestern United States should be prepared for a high frequency of poorly adapted progeny.