An Empirical Assessment of Transgene Flow from a Bt Transgenic Poplar Plantation

PLOS ONE, Dec 2019

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.

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An Empirical Assessment of Transgene Flow from a Bt Transgenic Poplar Plantation

January An Empirical Assessment of Transgene Flow from a Bt Transgenic Poplar Plantation Jianjun Hu 0 1 2 Jin Zhang 0 1 2 Xingling Chen 2 Jinhui Lv 1 2 Huixia Jia 0 1 2 Shutang Zhao 0 1 2 Mengzhu Lu 0 1 2 ☯ These authors contributed equally to this work. 2 2 0 Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry University , Nanjing , China , 3 Changchun Academy of Forestry , Changchun , China 1 State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry , Beijing , China 2 Editor: Shaojun Dai, Northeast Forestry University , CHINA 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 4ÊC. 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. - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by the National High-Tech R&D Program of China (2013AA102702 and 2011AA10020101). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Introduction 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. As long-lived plants, trees are exposed to the environment over a much longer time period than are annual crops [ 1, 2 ]. Poplar, as a fast-growing tree with 8±15 years in rotation, has been used for genetic transformation for both research and breeding [ 3, 4 ]. Cross-pollination of poplars in plantations with their wild relatives is of major concern due to the broad compatibility within and among species, even those belonging to different sections of Populus [ 5 ]. Several modeling and simulation methods have been proposed to measure the gene flow between poplar stands [ 6, 7 ], and co-dominant markers have been developed to monitor gene flow among species, even those belonging to different sections [8]. However, no empirical data on transgenic poplar plantations are available to address this issue. Poplars play important roles in afforestation and timber supply worldwide. In China, approximately 7 million hm2 of poplar plantations have been established for shelterbelt and timber production [ 9 ]. However, insects create severe damage to the plantations and cause an estimated annual loss of millions of US dollars. The infected trees are usually sprayed with pesticide or cut down in order to control the infestation, resulting in serious economic and ecological consequences [ 10 ]. Genetic engineering provides a promising tool for breeding superior poplar clones with improved tolerance to insects, drought, and/or wood properties. For example, insect-tolerant transgenic Populus nigra with the Bacillus thuringiensis toxin (Bt) gene was planted for a field test in 1994 and proved effective in avoiding leaf-insect damage [ 11 ]. To date, transgenic poplars are not only released in field trials but also planted as a commercial crop in plantation forestry [ 12 ]. To develop poplars that were more tolerant to insect attacks, Populus nigra trees were transformed with cry1Ac in 1993 and have been field tested since 1994. Bt poplars were first commercialized in 2001 and occupied 490 ha in China up through 2014. Transgenic poplar plantations have effectively inh (...truncated)


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Jianjun Hu, Jin Zhang, Xingling Chen, Jinhui Lv, Huixia Jia, Shutang Zhao, Mengzhu Lu. An Empirical Assessment of Transgene Flow from a Bt Transgenic Poplar Plantation, PLOS ONE, 2017, Volume 12, Issue 1, DOI: 10.1371/journal.pone.0170201