Vegetative growth after flowering through gibberellin biosynthesis regulates pod setting rate in soybean (Glycine max (L.) Merr.)

Pod setting rate in soybean is an important trait that determines pod number, which is highly correlated with seed yield. Using two soybean cultivars with different pod setting rates, we examined the relationship between plant growth regulation by gibberellin (GA) and pod setting rate. Plant growth rate (PGR) after flowering was significantly higher in ‘Fukuyutaka’ (low pod setting rate) than in ‘Kariyutaka’ (high pod setting rate); this difference was caused by increasing of GA biosynthesis-related genes expression. Additionally, pod setting rate in ‘Fukuyutaka’ was lower than that in ‘Kariyutaka’. Furthermore, when ‘Kariyutaka’ was treated with GA after flowering, the PGR increased and pod setting rate decreased. These results suggest that pod setting rate in soybean is regulated by vegetative growth after flowering through GA biosynthesis.