转基因抗虫棉花和玉米与节肢动物相关的生态安全性研究进展

Progress in ecological biosafety of insect-resistant transgenic cotton and corn in relation to arthropods

转基因抗虫棉花和玉米自1996年商业化种植以来,已取得显著的经济、生态和社会效益。与其相关的生态安全性,特别是其对非靶标生物的影响及靶标害虫的抗性监测和治理已成为人们普遍关注的话题。本文在大量室内和田间评价工作的基础上,系统综述了国内外研究在该领域内取得的进展。结果表明:由于Bt棉田和玉米田杀虫剂用量的减少,某些对Bt杀虫蛋白不敏感的非靶标植食害虫种群有上升的趋势;现阶段生产上推广种植的Bt棉花和玉米花粉对家蚕、柞蚕和蜜蜂等经济昆虫以及帝王斑蝶是安全的。杀虫剂用量的减少,降低了对天敌的杀伤力,Bt田中捕食性天敌的种类和数量均显著高于常规施药田;但Bt田内靶标害虫数量的减少和质量的降低,在一定程度上影响了寄生性天敌的种类和数量。Bt棉花和玉米的大面积种植对农田生态系统节肢动物群落结构无明显不利影响。靶标害虫田间抗性监测结果表明,无论在以大农场单一种植经营为主的发达国家如美国或澳大利亚,还是在以小农经营为主的多种寄主作物小规模交叉混合种植模式的发展中国家如中国或印度,田间并未出现10年前人们所关注和预测的靶标害虫种群抗性上升问题。究其原因,可能与发达国家严格执行了预防性的抗性治理对策及发展中国家独特的作物种植模式有关。尽管目前在田间尚未发现害虫对Bt作物产生抗性,但应用更多年份之后,害虫对Bt作物的抗性就很可能不是"是否"发生问题,而是"何时"发生的问题。因此,今后的研究重点应放在Bt棉花和玉米长期、大面积种植后,其对非靶标生物及靶标害虫抗性发展影响的长期生态效应上。

Since Bt cotton and corn were commercially planted in 1996, remarkable economic, ecological and social benefits have been obtained. However, ecological biosafety pertinent to their introduction has become a public concern, especially the potential impact of Bt crops on non-target organisms and evolution of resistance in target insect pests. The progress of laboratory and field assessment of Bt corn and cotton on non-target arthropods and resistance management of target insects were reviewed in this article. Research has shown that field populations of some non-target herbivorous insects in Bt crops may increase due to the removal of wide-spectrum insecticides. The pollen or nectar of Bt corn and cotton as food sources of honey bees or the natural drift of pollen onto food plants of silkworms have no direct or indirect detrimental influence on these beneficial insects as well as the monarch butterfly,Danaus plexippus. Bt cotton and corn may affect natural enemies indirectly by decreasing the population of lepidopteran insects that serve as hosts of parasitoids or predators. Population densities of predators in Bt fields were significantly higher than those in non-Bt fields treated with insecticides for control of target pests. However, population size and species richness of parasitoids might decrease due to lower density or poor quality of their host insects. There were no significant negative effects of Bt cotton and corn on the abundance and diversity of foliar and soil arthropod communities. Resistance monitoring demonstrated that resistance of target insects to Bt cotton and corn has not occurred in fields after 10 years of commercial use, either in large-scale farming system as in the U.S. and Australia or in small-scale planting of Bt cotton in as China and India where several other non-Bt host crops of the target insects can serve as natural refuge. The absence of field resistance to date is presumed to be due to the implementation of refuge strategy in the developed countries and the unique cropping pattern in the developing countries. However, caution for resistance evolution continues to be warranted because resistance to Bt crops most likely remains a question of not ＂if＂ but ＂when＂. Therefore, future work should be emphasized on the impact of long-term and large-scale planting of Bt cotton and corn on non-target organisms and resistance evolution of target pests.