Ecological Assessment Of Transgene Escape From Transgenic Soybean (Glycine Max)

China is the original center of cultivated soybean (Glycine max) and soybean is an important crop in China. There are abundant genetic resources of wild soybean(G. soja) in nature in China. The potential ecological risk has drawn increasing attention as the release of transgenic soybean into the environment. The study, using mechanical damage to simulate herbivory, investigated the fitness of hybrids in wild soybean obtaining Bt gene from transgenic soybean by gene flow in order to reveal the fate of transgene in nature and to provide references for transgene management in farming system. In the same time, the fitness of hybrid F1, which was formed by hand-crossing transgenic soybean resistant to glyphosate herbicide and its nontransgenic near-isogenic line to wild soybean, respectively, was evaluated to provide a preliminary study of the ecological impacts of the escape of transgenes. The main results are given as follows:Leaf-cutting simulation experiments showed that the wild soybean in different treatments, i.e. different levels of pest pressure, has different response to the simulated injury. There was a same trend in various geographical populations of wild soybean in the leaf-cutting treatments. There was no significant difference in seed number, grain weight, biomass between the wild soybean control and the plants of cutting1/4and2/4of leaves. The treatment of cutting3/4leaves resulted in significantly lower plant growth and reproduction (e.g. seed number, biomass). The results suggest that the insect resistance has selective advantage in nature, but this advantage shall base on the levels of selection pressure. At the absence or lower pest pressure, there is no significant competitive advantage in seed production, biomass and other growth aspects in the resistant plants. At moderate or higher stress, the resistant plants have higher fitness than the sensitive plants. Under more serious pest pressure, there is a high risk of invasion into the wild populations and stabilization of insect-resistant transgene. Leaf cutting of wild soybean had no significant impact on seed germination. Wild soybean remained a relatively high dormancy rate that permits the persistence of the introgressed wild seeds in the soil.Hybridization experiment showed that the hand-crossing rate was very low between the cultivated soybean and wild soybean. In this study, the hybridization using MIYUN wild population as female and herbicide-resistant genetically modified soybeans (AG5601) as male performed the highest hybridization rate that only hit9%. The result implies that wild soybean in MIYUN region has the highest compatibility to genetically modified soybean. Hybrid between wild population and non-genetically modified soybean was only obtained from MIYUN population, and no hybrid was formed by the remaining two wild populations. It was suggested that the pollen viability of transgenic soybean could be higher than non-transgenic pollen viability. If the competitive ability of transgenic pollen is higher than non-transgenic pollen, it will promote the formation of hybrids in the wild and increase the incidence of transgene escape.In greenhouse experiments, the fitness of hybrid F1formed between cultivated soybean and wild soybean was estimated by vegetative growth, pod number, seed number, biomass, grain weight and other indicators that based on both vegetative and reproductive growth. By comparing the hybrid F1generation to wild soybean, we found that there were no significant difference in the pod formation and biomass production. Seed number of hybrid was significantly lower than the wild populations. The herbicide resistance gene did not increase the fitness of hybrids. Fitness of hybrids was similar to that of wild soybean, while some growth characteristics even decreased. This does not imply the absence of any ecological risk of escape of the transgene. Obviously, herbicide resistance has selective advantage at high herbicide application in farmland. However, the fitness of the hybrid and wild populations did not differ significantly under the absence of herbicide pressure or at low pressure, which is a common situation in natural population. Therefore, the hybrids with resistance gene are likely to retain and stabilize in nature.