Date Published: January 13, 2017
Publisher: Public Library of Science
Author(s): Jianjun Hu, Jin Zhang, Xingling Chen, Jinhui Lv, Huixia Jia, Shutang Zhao, Mengzhu Lu, Shaojun Dai.
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.
A major concern regarding the commercialization of transgenic forest trees is gene flow, through which transgenes may spread from transgenic trees to natural forests. Although gene flow is a very common natural phenomenon and an important process for evolution, the movement of transgenes from genetic modified plants to wild related populations may be considered undesirable and lead to undesirable environmental consequences, such as more aggressive weeds, germplasm loss, or increased non-target organism and biodiversity losses.
The concern about transgene escape via the pollen or seeds of transgenic trees regards a possible negative effect on the natural forest ecological system, and this concern has hurdled the application of transgenic trees . Thus, it is important to understand the pollen dispersal, seed production and seedling survival of transgenic trees. Previous studies have used established stands and simulation models to explore the consequences of introducing new genes into the environment. In this study, we take advantage of the commercialized insect-resistance transgenic poplar  and for the first time have provided empirical data to evaluate the possibility of transgene flow through pollen or seeds.