An Empirical Assessment of Transgene Flow from a <i>Bt</i> 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 plantation carrying the Bacillus thuringiensis toxin gene (Bt poplar) and the survival of Bt poplar seeds. The resultant Bt poplar seeds occurred at a frequency of ~0.15% at 0 m to ~0.02% at 500 m from the Bt poplar plantation. The germination of Bt poplar seeds diminished within three weeks in the field (germination rate from 68% to 0%) compared to 48% after three weeks of storage at 4°C. The survival rate of seedlings in the field was 0% without any treatment but increased to 1.7% under the addition of four treatments (cleaning and trimming, watering, weeding, and covering with plastic film to maintain moisture) after being seeded in the field for eight weeks. The results of this study indicate that gene flow originating from the Bt poplar plantation occurred at an extremely low level through pollen or seeds under natural conditions. This study provides first-hand field data on the extent of transgene flow in poplar plantations and offers guidance for the risk assessment of transgenic poplar plantations.为评估转基因杨树人工林对生态系统的潜在影响，本研究针对携带苏云金杆菌（Bacillus thuringiensis，Bt）毒素基因的成熟雄性转基因欧洲黑杨（Populus nigra）人工林，分析了其基因流的发生频率与传播距离，并检测了转基因Bt杨树种子的存活情况。研究结果显示，距该Bt杨树人工林0米处，Bt杨树种子的检出频率约为0.15%；至500米处，该频率降至约0.02%。田间条件下，Bt杨树种子的萌发能力在三周内快速衰减：其田间萌发率由初始的68%降至0%；而在4℃低温储存三周后，其萌发率仍可达48%。田间播种8周后，未施加任何管护措施的Bt杨树幼苗存活率为0%；在施加清理修剪、浇水、除草及覆膜保墒四项管护措施后，幼苗存活率提升至1.7%。本研究结果表明，自然条件下，源自该Bt杨树人工林的基因通过花粉或种子发生漂移的水平极低。本研究提供了杨树人工林中转基因漂移程度的一手田间实测数据，可为转基因杨树人工林的生态风险评估提供科学参考。