Seed Coat Cracking of Soybean (Glycine max [L.] Merr.) After Soaking and Cooking

Seed coat cracking after soaking (SCAS) and after cooking (SCAC) are unfavorable traits associated with soybeans for food uses, such as cooked and seasoned beans (nimame) and fermented steamed beans (natto) because they cause an inferior appearance of the products and clogging of the production lines. The variation and causes of SCAS and SCAC among cultivars have not yet been clarified, but if they are determined genetically, genetic modification could be possible. Cultivars showed considerable variations in SCAS and SCAC. Significantly positive seasonal correlations of SCAS (Spearman's rank correlation coefficient, rho = 0.518) and of SCAC (rho = 0.681) were observed among recombinant inbred lines (RILs) derived from the cross between cultivars Nattoshoryu and Hyokeikuro 3. Quantitative trait locus (QTL) analyses and statistical analyses using generalized linear models showed that QTLs for SCAS (qSCAS1, qSCAS2, and qSCAS3) and SCAC (qSCAC1 and qSCAC2) were located on chromosomes 4 (linkage group [LG]: C1), 6 (LG: C2), and 8 (LG: A2) of the RILs. Interactions between QTLs were also observed. SCAS and SCAC are traits controlled by QTLs, which could provide significant insight into their causes and mechanisms. These undesirable characteristics could be improved through breeding.