Seed germination and the viability of ungerminated seeds
Seed dormancy is an important component of plant fitness that causes a delay in germination until the arrival of a favorable growth season (Graeber et al. 2012). The high seed dormancy of wild soybean is very important for seed survival in the soil and delays seed germination until environmental conditions are correct (Wang and Li 2012). If seeds of hybrids between wild and GM soybean could have stronger dormancy like their wild relatives, it may favor the formation of a longer-lived seed bank enriched with the transgenic seeds.
In the present study, 21-day seed germination results showed that, although F1, F2 and F3hybrid seed germination was significantly higher than that of wild soybean, about half of the F1, F2 and F3 seeds did not germinate, and most ungerminated F1, F2, F3 seeds were deemed normal, i.e., not changed in shaped, size or color. After their partial seed coats were removed, almost all the ungerminated seeds were viable, and the five-day seed germination of all observed hybrid seeds was above 87.5%, suggesting that hybrid derivatives between wild and GM soybean had similar germination characteristics as wild soybean, F1, F2 and F3 hybrid seeds can persist for considerable time in the soil seed bank.