Soybean Maturity Gene Effects on Seed Coat Pigmentation and Cracking in Response to Low Temperatures

Abstract

Exposure of soybean [Glycine max (L.) Merr.] to chilling temperatures (about 15°C) at flowering induces browning around the hilum region and cracking of the seed coats. Both pigmentation and cracking degrade the external appearance of soybean seeds and reduce their commercial value. An earlier study showed that some alleles at maturity loci E1 to E5 were associated with intensity of pigmentation and cracking. The objective of this study was to evaluate the effect of alleles at maturity locus E7 and the combination effect of E3 and E4 on the intensity of seed coat pigmentation and cracking. Soybean cv. Harosoy (ele2E3E4e5E7) and its near-isogenic lines Harosoy-e3, Harosoy-e4, Harosoy-e3e4, and Harosoy-e3e4e7 were exposed to 15°C for 2 wk beginning 8 d after flowering. Control plants were grown in a greenhouse throughout their entire life cycle, whereas the treated plants were transferred from the greenhouse to a phytotron for the chilling treatment. Intensities of both pigmentation and cracking were increased by recessive allele e3 and reduced by recessive allele e4. Harosoy-e3e4 showed an intermediate degree of pigmentation and cracking relative to Harosoy-e3 and Harosoy-e4. These results suggest that effects of maturity genes E3 and E4 may be additive and that combination effects may be roughly estimated from individual gene action. Harosoy-e3e4e7 exhibited a higher degree of pigmentation and cracking than Harosoy-e3e4, suggesting that dominant allele E7 can reduce the degree of pigmentation and cracking, similar to the El, E2, E3, and ES loci. These results suggest that selection for the appropriate combination of maturity genes is effective to adjust time to flowering and maturity and to produce high quality seeds at high latitude regions. The e4 allele may be especially useful in reducing seed coat pigmentation and cracking in soybean cultivars adapted to high latitudes.