Department of Entomology, University of Arizona, Tucson, AZ, USA.
J Econ Entomol. 2023 Oct 10;116(5):1804-1811. doi: 10.1093/jee/toad145.
The polyphagous pest Helicoverpa zea (Lepidoptera: Noctuidae) has evolved practical resistance to transgenic corn and cotton producing Cry1 and Cry2 crystal proteins from Bacillus thuringiensis (Bt) in several regions of the United States. However, the Bt vegetative insecticidal protein Vip3Aa produced by Bt corn and cotton remains effective against this pest. To advance knowledge of resistance to Vip3Aa, we selected a strain of H. zea for resistance to Vip3Aa in the laboratory. After 28 generations of continuous selection, the resistance ratio was 267 for the selected strain (GA-R3) relative to a strain not selected with Vip3Aa (GA). Resistance was autosomal and almost completely recessive at a concentration killing all individuals from GA. Declines in resistance in heterogeneous strains containing a mixture of susceptible and resistant individuals reared in the absence of Vip3Aa indicate a fitness cost was associated with resistance. Previously reported cases of laboratory-selected resistance to Vip3Aa in lepidopteran pests often show partially or completely recessive resistance at high concentrations and fitness costs. Abundant refuges of non-Bt host plants can maximize the benefits of such costs for sustaining the efficacy of Vip3Aa against target pests.
多食性害虫棉铃虫（鳞翅目：夜蛾科）已经在美国的几个地区进化出了对转 Bt 玉米和棉花产生的 Cry1 和 Cry2 晶体蛋白的实际抗性。然而，Bt 玉米和棉花产生的 Vip3Aa 细菌杀虫蛋白仍然对这种害虫有效。为了深入了解对 Vip3Aa 的抗性，我们在实验室中选择了对 Vip3Aa 具有抗性的棉铃虫品系。经过 28 代的连续选择，相对于未用 Vip3Aa 选择的品系（GA），选择品系（GA-R3）的抗性比为 267。抗性是常染色体的，在杀死 GA 所有个体的浓度下几乎完全是隐性的。在没有 Vip3Aa 的情况下，含有敏感和抗性个体的异质品系中抗性的下降表明，抗性与适应度成本有关。先前报道的在鳞翅目害虫中实验室选择对 Vip3Aa 的抗性的情况通常显示在高浓度下具有部分或完全隐性抗性和适应度成本。大量非 Bt 宿主植物的避难所可以最大限度地提高这些成本对维持 Vip3Aa 对靶标害虫的功效的益处。
