Department of Entomology, University of Arizona, Tucson, AZ, USA.
Pest Manag Sci. 2018 Mar;74(3):627-637. doi: 10.1002/ps.4746. Epub 2017 Nov 15.
In pests with inherently low susceptibility to Bacillus thuringiensis (Bt) toxins, seasonal declines in the concentration of Bt toxins in transgenic crops could accelerate evolution of resistance by increasing the dominance of resistance. Here, we evaluated Helicoverpa zea survival on young and old cotton plants that produced the Bt toxins Cry1Ac and Cry1F or did not produce Bt toxins.
Using a strain selected for resistance to Cry1Ac in the laboratory, its parent strain that was not selected in the laboratory, and their F progeny, we showed that resistance to Cry1Ac + Cry1F cotton was partially dominant on young and old plants. On Cry1Ac + Cry1F cotton, redundant killing was incomplete on young plants but nearly complete on old plants. No significant fitness costs on non-Bt cotton occurred on young plants, but large recessive costs affected survival on old plants. Simulation models incorporating the empirical data showed that the seasonal changes in fitness could delay resistance to Cry1Ac + Cry1F cotton by inducing low equilibrium frequencies of resistance alleles when refuges are sufficiently large.
Our results suggest that including effects of seasonal changes in fitness of pests on Bt crops and refuge plants can enhance resistance risk assessment and resistance management. © 2017 Society of Chemical Industry.
在对苏云金芽孢杆菌（Bt）毒素固有敏感性低的害虫中，转 Bt 作物中 Bt 毒素浓度的季节性下降可能通过增加抗性的优势，加速抗性的进化。在这里，我们评估了产生 Cry1Ac 和 Cry1F Bt 毒素或不产生 Bt 毒素的棉花植株的年轻和老植株上的棉铃虫的存活情况。
使用在实验室中选择 Cry1Ac 抗性的品系、未在实验室中选择的其亲本品系及其 F 代，我们表明 Cry1Ac + Cry1F 棉上对 Cry1Ac 的抗性在年轻和老植株上部分显性。在 Cry1Ac + Cry1F 棉上，对年轻植株的冗余杀伤不完全，但对老植株的杀伤几乎完全。在年轻植株上，非 Bt 棉上没有显著的生存成本，但对老植株的生存有很大的隐性成本。将经验数据纳入的模拟模型表明，当避难所足够大时，通过在低平衡频率下诱导抗性等位基因，季节性变化的适应性可能会延迟对 Cry1Ac + Cry1F 棉的抗性。
我们的研究结果表明，在 Bt 作物和避难所植物中包含害虫适应季节性变化的影响，可以增强对抗性的风险评估和抗性管理。© 2017 化学工业协会。
