Empirical assessment of transgene flow from transgenic poplar plantation

To assess the possible impact of transgenic poplar plantations on the ecosystem, we analyzed the frequency and distance of gene flow from a mature male transgenic Populus nigra carried Bacillus thuringiensis toxin gene (Bt-OE poplar) plantation, and the survival of Bt-OE poplar seeds as well. The resultant Bt-OE poplar seeds occurred at a frequency from ~0.15% at 0 m to ~0.02% at 500 m far away from the Bt-OE poplar. The Bt-OE poplar seeds weaken and even lost germinated activation within 3 weeks in the field (from 68% to 0%), compared to the 48% germination rate after 3 weeks in 4°C. The survival rate of seedlings in the field is 0% without any treatments, but increased to 1.7% under four treatments (Clean and trim, watering, weeding, and cover with plastic to keep moisture) together after seeded in the field for eight weeks. Results of this study indicate that gene flow originated from Bt-OE poplar plantation through pollen and seed could happen at a very low rate and in a limited range in natural conditions. This study provide the first-hand field data on the extent of transgene flow in poplar plantations, and offer guidance for risk assessment of transgenic poplar plantations.