Detection of the Genetic Factors Affecting the Number of Seeds per Pod in Soybean

The number of seeds per pod (NSP) is a component of seed yield in soybean [Glycine max (L.) Merr.]. NSP varies in the cultivars, but the molecular mechanisms of such control remain unclear. Standard Japanese cultivars showed approximately 2.0 seeds per pod on average. In contrast, ‘INDIA (IC 24527)’ showed more than 3.1 seeds per pod, and the frequency of four-seeded pods was approximately 30%. The genetic factors increasing NSP in ‘INDIA’ could be used to improve soybean yield. We have investigated quantitative trait loci (QTLs) for NSP in three different environments, utilizing the recombinant inbred population derived from the cross between ‘INDIA’ and a US cultivar ‘Jack’. Four stable QTLs for NSP were identified on independent chromosomes in the population. Among the four QTLs, ‘INDIA’ alleles at three loci and ‘Jack’ allele at another locus increased NSP. The combination of them increased more than 0.5 seeds per pod than those of the opposite alleles, and enabled the emergence of five-seeded pods. In addition, we evaluated the relationship of the four QTLs with other components of seed yield, Single seed weight (SSW) and number of pods per plant (NPP), in addition to yield per plant.