Aboveground biomass
In this study, no significant differences were found in the aboveground biomass between wild soybean and F1 plants, while the aboveground biomass of the F2 population and F3 population was significantly higher than that of their female parent; thus, hybrids between wild soybean and GM soybean, especially F2 and F3, had stronger vegetative growth vigor than wild soybean. A similar conclusion was reported by Guan et al. (2015), who measured the F1 and F2 hybrids of two wild soybeans and glyphosate-resistant soybean under greenhouse and field conditions and found that GM F1 hybrids had similar dry weights of the aboveground biomass, while both GM and non-GM F2 had a significantly higher aboveground biomass than wild soybean in the field. Hybrid plants with higher biomass were also observed in Brassica rapa (Moon et al. 2007; Stewart et al. 2010), rice (Langevin et al. 1990) and sunflower (Mercer et al. 2007), and the increased growth of hybrids compared with that of wild plants might be due to the paternal parents enhancing the plant performance of the hybrid (Mercer et al. 2007).