A pubescence color gene enhances tolerance to cold-induced seed cracking in yellow soybean

In yellow soybean, severe cold weather causes seed cracking on the dorsal side. Yellow soybeans carry the I or ii allele of the I locus and have a yellow (I) or pigmented (ii) hilum. We previously isolated an additional allele, designated as Ic, of the I locus, and reported that yellow soybeans with the IcIc genotype may be tolerant to cold-induced seed cracking. The Ic allele by itself, however, does not confer high tolerance. The association of a pubescence color gene (T) with suppression of low-temperature-induced seed coat deterioration has been previously reported. In the present study, we tested whether T is effective for the suppression of cold-induced seed cracking using two pairs of near-isogenic lines for the T locus in the iiii or IcIc background. In both backgrounds, the cracked seed rate of the near-isogenic line with the TT genotype was significantly lower than that with the tt genotype, which indicates that T has an inhibitory effect on cold-induced seed cracking. Furthermore, we also showed that gene pyramiding of Ic and T can improve tolerance to cold-induced seed cracking. Our findings should aid the development of highly SC-tolerant cultivars in soybean breeding programs.