Department of Entomology, University of Arizona, Tucson, AZ.
J Econ Entomol. 2020 Oct 16;113(5):2041-2051. doi: 10.1093/jee/toaa138.
For delaying evolution of pest resistance to transgenic corn producing Bacillus thuringiensis (Bt) toxins, limited data are available to compare the effectiveness of refuges of non-Bt corn planted in seed mixtures versus blocks. Here we addressed this issue in the ear-feeding pest Helicoverpa zea Boddie by measuring its survival and development in the laboratory on ears from field plots with 90% Cry1A.105 + Cry2Ab corn and 10% non-Bt corn planted in a seed mixture or blocks. We compared a strain of H. zea selected for resistance to Cry1Ac in the laboratory, its parent strain not selected in the laboratory, and their F1 progeny. The relative survival of the F1 progeny and dominance of resistance were higher on ears from Bt plants in the seed mixture than the block. Half of the kernels in ears from non-Bt plants in the seed mixture produced both Cry1A.105 and Cry2Ab. However, survival on ears from non-Bt plants did not differ between the block and seed mixture. In simulations based on the observed survival, resistance to Cry1A.105 + Cry2Ab corn evolved faster with the seed mixture than the blocks, because of the higher dominance of resistance in the seed mixture. Increasing the refuge percentage improved durability of Cry1A.105 + Cry2Ab corn more for the blocks than the seed mixture. These findings imply that, for a given percentage of non-Bt corn, resistance of H. zea and other ear-feeding pests to multi-toxin Bt corn is likely to evolve faster for seed mixtures than blocks.
为了延缓害虫对生产苏云金芽孢杆菌（Bt）毒素的转基因玉米的抗药性进化，目前可用的数据有限，无法比较在种子混合物中种植非 Bt 玉米避难所与种植在块状中的非 Bt 玉米避难所的效果。在这里，我们通过测量在田间试验田中收获的玉米穗上耳食性害虫烟青虫（Helicoverpa zea Boddie）的存活率和发育情况，来解决这个问题。田间试验田的 90% Cry1A.105 + Cry2Ab 玉米和 10%非 Bt 玉米种植在种子混合物或块状中。我们比较了实验室中对 Cry1Ac 选择的烟青虫品系、未在实验室中选择的烟青虫亲本品系及其 F1 后代。F1 后代的相对存活率和抗药性优势在种子混合物中的 Bt 植株上的玉米穗上比在块状中的更高。在种子混合物中非 Bt 植株的玉米穗上，有一半的玉米粒同时产生了 Cry1A.105 和 Cry2Ab。然而，在非 Bt 植株的玉米穗上的存活率在块状和种子混合物之间没有差异。根据观察到的存活率进行模拟，由于在种子混合物中抗药性优势更高，Cry1A.105 + Cry2Ab 玉米对烟青虫的抗性进化速度比块状更快。增加避难所的比例会提高 Cry1A.105 + Cry2Ab 玉米的耐用性，对块状的效果比对种子混合物的效果更好。这些发现表明，对于给定比例的非 Bt 玉米，与块状相比，种子混合物中烟青虫和其他耳食性害虫对多毒素 Bt 玉米的抗药性更有可能更快进化。
