Department of Entomology, University of Arizona, Tucson, AZ 85721, USA.
J Econ Entomol. 2010 Oct;103(5):1821-31. doi: 10.1603/ec10087.
Evolution of resistance by pests can reduce the efficacy oftransgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis Berliner (Bt). In conjunction with refuges of non-Bt host plants, fitness costs can delay the evolution of resistance. Furthermore, fitness costs often vary with ecological conditions, suggesting that agricultural landscapes can be manipulated to magnify fitness costs and thereby prolong the efficacy of Bt crops. In the current study, we tested the effects of four species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) on the magnitude and dominance of fitness costs of resistance to Bt toxin CrylAc in pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae). For more than a decade, field populations of pink bollworm in the United States have remained susceptible to Bt cotton Gossypium hirsutum L. producing CrylAc; however, we used laboratory strains that had a mixture of susceptible and resistant individuals. In laboratory experiments, dominant fitness costs were imposed by the nematode Steinernema riobrave Cabanillas, Poinar, and Raulston but no fitness costs were imposed by Steinernema carpocapsae Weiser, Steinernema sp. (ML18 strain), or Heterorhabditis sonorensis Stock, Rivera-Orduño, and Flores-Lara. In computer simulations, evolution of resistance to Cry1Ac by pink bollworm was substantially delayed by treating some non-Bt cotton refuge fields with nematodes that imposed a dominant fitness cost, similar to the cost observed in laboratory experiments with S. riobrave. Based on the results here and in related studies, we conclude that entomopathogenic nematodes could bolster insect resistance management, but the success of this approach will depend on selecting the appropriate species of nematode and environment, as fitness costs were magnified by only two of five species evaluated and also depended on environmental factors.
害虫的抗药性进化会降低产生苏云金芽孢杆菌（Bt）杀虫毒素的转基因作物的功效。与非 Bt 宿主植物避难所相结合，适应成本可以延缓抗药性的进化。此外，适应成本通常随生态条件而变化，这表明可以操纵农业景观来放大适应成本，从而延长 Bt 作物的功效。在当前的研究中，我们测试了四种昆虫病原线虫（Steinernematidae 和 Heterorhabditidae）对Bt 毒素 Cry1Ac 抗性的适应成本的幅度和优势的影响，粉红棉铃虫，Pectinophora gossypiella（Saunders）（鳞翅目：Gelechiidae）。十多年来，美国的粉红棉铃虫田间种群仍然对产生 Cry1Ac 的Bt 棉花棉属保持敏感；然而，我们使用了具有敏感和抗性个体混合物的实验室品系。在实验室实验中，线虫 Steinernema riobrave Cabanillas、Poinar 和 Raulston 施加了显性适应成本，但 Steinernema carpocapsae Weiser、Steinernema sp.（ML18 株）或 Heterorhabditis sonorensis Stock、Rivera-Orduño 和 Flores-Lara 没有施加适应成本。在计算机模拟中，通过用对施加显性适应成本的线虫处理一些非 Bt 棉花避难所，大大延迟了粉红棉铃虫对 Cry1Ac 的抗药性进化，这类似于在实验室实验中用 S. riobrave 观察到的成本。基于这里和相关研究的结果，我们得出结论，昆虫病原线虫可以增强昆虫抗药性管理，但这种方法的成功将取决于选择适当的线虫和环境，因为只有评估的五个线虫物种中的两个和环境因素放大了适应成本。
