Soybean maturity and pubescence color genes improve chilling tolerance

Exposure of soybean [Glycine max (L.) Merr.] to chilling temperatures (10-18 degrees C) at flowering reduces seed yield and induces browning around the hilum region and cracking of the seed coats. Previous studies revealed that alleles at maturity loci E1 to E5 and E7 were associated with the intensity of pigmentation and cracking, and that genotypes with the pubescence color allele T are associated with less seed yield reduction under low temperature conditions. The first objective of this study was to evaluate the combination effect of maturity genes between E1 and E3E4 on the intensity of seed coat pigmentation and cracking. The second objective was to evaluate the combination effects of El, E3E4, and T on weight of seed per plant under chilling treatments. For the seed quality experiment, soybean cv. Harosoy (ele2E3E4e5E7t) and its near-isogenic lines (NILs), Harosoy-E1, Harosoy-e3e4, and Harosoy-E1e3e4, were exposed to 15 degrees C for 2 wk beginning 8 d after flowering. Harosoy-E1e3e4 had an intermediate degree of pigmentation and cracking relative to Harosoy-E1 and Harosoy-e3e4, suggesting that the effects of El and E3E4 may be additive. For the yield component experiments, Harosoy, Harosoy-T, Harosoy-E1e3e4, and Harosoy-E1e3e4T were exposed to 15 C in 2002 and 18/13 degrees C with 55% shading in 2003 for 4 wk from flowering. Weight of seed per plant in NILs with E1e3e4 was higher than NILs with e1E3E4 under chilling treatments. Further, NILs with T produced higher weight of seed per plant compared with NILs with t under chilling treatments. The above results suggest that allelic combination of E1e3e4 is preferable to e1E3E4 to enhance quality and yield of seeds under chilling conditions. The dominant T allele may also be useful to further improve chilling tolerance.