Stability verification of the effects of stem determination and earliness of flowering on green stem disorder of soybean against genetic background and environment

Green stem disorder (GSD) of soybean reduces harvesting efficiency and negatively impacts seed appearance when mechanical harvesting is employed. Two recombinant inbred populations were investigated for the effects of segregating stem determination and flowering time on GSD at two different locations, Kyoto and Akita, over two years. Although the severity of GSD of each line varied considerably with the location, the scores showed significant correlation with the environment. Quantitative trait locus (QTL) analysis revealed a strong and consistent QTL for GSD severity in one population of recombinant inbred lines (RILs) across the environments at the Dt1 locus, which governs stem growth habits, and the determinate growth genotypes showed evident symptoms of GSD. However, QTLs were not detected near the Dt1 locus in the other population. Thus, it was unclear if the responsible gene was identical to the stem determination gene. The early flowering genotype showed a more severe symptom of GSD in both populations, but this effect was dependent on the allele at the Dt1 locus. The effect of another QTL detected in the latter population also depended on the allele at the Dt1 locus. Our results indicated that the genetic factor at the Dt1 locus and the factor controlling flowering time influenced the severity of GSD at each location and year and that their effects and interaction complicated the genetic control of the occurrence of GSD