转基因逃逸及其环境生物安全评价研究进展——抗虫水稻案例分析

转基因技术研发为提高我国水稻产量和减少劳动力投入提供了巨大机遇。我国对转基因水稻研发进行了大量的投入,目前已培育了具有不同新性状的转基因水稻品系,许多品系已进入生物安全评价阶段。风险评价对转基因水稻的安全生产至关重要,是其商品化生产之前必须解决的问题,其中包括转基因逃逸及其潜在环境影响。对水稻抗虫转基因逃逸及其潜在环境风险的评价包括3个重要环节：（1）通过田间试验和模型模拟检测转基因漂移到非转基因栽培稻及其野生近缘种的频率;（2）检测转基因在栽培稻和野生近缘种后代中的表达;（3）确定转基因对野生近缘种群体适合度和进化潜力的影响。大量研究表明,在近距离的空间范围内栽培稻品种之间的基因漂移频率很低（〉0.1%）,但栽培稻与其野生近缘种的基因漂移频率变异很大。进一步研究还表明,Bt抗虫转基因在栽培稻与普通野生稻后代中均能正常表达,但在其不同生长阶段,表达量有很大变异。在有较高水平的害虫虫压下,含有抗虫转基因的栽培稻及野生近缘种杂交后代与不含转基因的对照相比,抗虫性显著提高且适合度利益明显;但是,在虫害发生水平较低时,含有抗虫转基因的群体与不含抗虫转基因的群体相比没有显著的适合度优势。综上,转基因逃逸到非转基因水稻的频率极低,并且可以通过空间隔离阻断其逃逸。虽然抗虫转基因向杂草稻以及与栽培稻距离较近的野生稻群体的逃逸无法避免,但是野生稻和杂草稻群体周围环境中的总体虫压较低,所以基因漂移带来的环境影响应十分有限。

Assessing transgene escape and its environmental biosafety impacts: a case study in insect resistant transgenic rice

The development of genetically engineered（ GE） rice offers more opportunities to increase rice productivity and to reduce labor / resource inputs. China has invested tremendously in the research and development of transgenic biotechnology and GE crops,including rice. Consequently,a large number of GM rice lines with diverse novel traits has been developed. Many GE rice lines are undergoing biosafety assessment that is key to the safe use of GE rice. Potential environmental impact caused by transgene escape to wild relatives is still a great concern for the commercial release of GE rice. Three platforms are important to assess potential environmental impacts of insect-resistance transgene flow in rice：（ 1） estimating frequencies of transgene flow from GE to non-GE rice and wild relatives through field experiments and model simulation;（ 2） examining the expression of transgenes in wild relatives of rice;and（ 3） estimating the life-cycle fitness of transgenes introgressed to rice wild relatives. Crop-to-crop gene flow is extremely low（ 0.1%） at close spacing,while crop-to-wild gene flow varies significantly,up to 3% in our studies. The Bt transgene expresses normally in crop-wild progeny although with considerable variation at different growth stages. Transgenic hybrid progeny derived from crop-wild / weed crosses showed increased fitness under insect pressure,but no significant differences in fitness were detected between transgenic and non-transgenic populations under low insect pressure. The frequency of transgene escape to non-GE rice is low and can be managed by spatial isolation. It is difficult to stop the flow of the insect-resistance transgenes to wild / weedy rice populations that coexist with GE rice. Given the low ambient insect pressure in habitats where wild / weedy rice populations occur,the environmental impact caused by such gene flow might be limited.