Association of Soybean Genes I and T with Low‐Temperature Induced Seed Coat Deterioration

Abstract

Exposure of soybean [Glycine max (L.) Merr.] to chilling temperatures (about 15°C) at flowering (R3–R4 stage) induces browning around the hilum region and cracking of the seed coats. Objectives of this study were to precisely evaluate the effect of chilling treatment on flowers at different developmental stages on the intensity of seed coat pigmentation and to determine the effects of genes T (responsible for pubescence and seed coat color) and I (responsible for the distribution of seed coat color) on seed coat pigmentation and cracking by glasshouse experiments. Tokei‐797, a cultivar with yellow hilum and gray pubescence (I/I, t/t), was exposed to 15°C for 2 wk beginning at 2, 5, 7, 12, 17, and 22 d after anthesis. Pigmentation increased with flower age at the time of treatment and was intense in the treatments, which started from 4 to 11 DAO (days after opening of individual flowers) and decreased thereafter. Harosoy and its two near‐isogenic lines, L67‐38 and L66‐707, were exposed to 15°C for 2 wk beginning at 8 d after anthesis (DAA). Harosoy has yellow hilum and gray pubescence (I/I, t/t). L67‐38 has buff hilum and gray pubescence (i‐i/i‐i, t/t) while L66‐707 has yellow hilum and brown pubescence (I/I, T/T). Seed coats of L67‐38 developed more intense pigmentation around the hilum region than Harosoy. In contrast, pigmentation of L66‐707 was restricted to the hilum. L67‐38 had a higher degree of cracking, while L66‐707 had a significantly lower degree of cracking than Harosoy. The T/t and I/i‐i genes are associated with the degree of pigmentation and cracking in response to chilling temperatures.