Abstract 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.

中文翻译：

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种子混合物中 Bt 和非 Bt 植物之间的基因流动增加了 Helicoverpa zea（鳞翅目：夜蛾科）对金字塔型 Bt 玉米的抗性优势

摘要 为了延迟害虫对产生苏云金芽孢杆菌 (Bt) 毒素的转基因玉米的抗性进化，可用于比较种子混合物中种植的非 Bt 玉米避难所与块状种子的避难所有效性的数据有限。在这里，我们解决了采耳害虫 Helicoverpa zea Boddie 中的这个问题，方法是在实验室中测量田间地块中穗的存活和发育，其中 90% Cry1A.105 + Cry2Ab 玉米和 10% 非 Bt 玉米种植在种子混合物中或块。我们比较了实验室中针对 Cry1Ac 抗性选择的玉米 H. 菌株、实验室未选择的亲本菌株及其 F1 后代。F1 后代的相对存活率和抗性优势在种子混合物中 Bt 植物的穗上高于块。种子混合物中来自非 Bt 植物的穗中的一半籽粒产生 Cry1A.105 和 Cry2Ab。然而，块状和种子混合物在非 Bt 植物穗上的存活率没有差异。在基于观察到的存活率的模拟中，种子混合物对 Cry1A.105 + Cry2Ab 玉米的抗性进化得比块更快，因为种子混合物中抗性的优势更高。与种子混合物相比，增加避难所百分比提高了 Cry1A.105 + Cry2Ab 玉米块的耐久性。这些发现意味着，对于给定百分比的非 Bt 玉米，玉米种子和其他采耳害虫对多毒素 Bt 玉米的抗性可能比块状种子混合物进化得更快。在基于观察到的存活率的模拟中，种子混合物对 Cry1A.105 + Cry2Ab 玉米的抗性进化得比块更快，因为种子混合物中抗性的优势更高。与种子混合物相比，增加避难所百分比提高了 Cry1A.105 + Cry2Ab 玉米块的耐久性。这些发现意味着，对于给定百分比的非 Bt 玉米，玉米种子和其他采耳害虫对多毒素 Bt 玉米的抗性可能比块状种子混合物进化得更快。在基于观察到的存活率的模拟中，种子混合物对 Cry1A.105 + Cry2Ab 玉米的抗性进化得比块更快，因为种子混合物中抗性的优势更高。与种子混合物相比，增加避难所百分比提高了 Cry1A.105 + Cry2Ab 玉米块的耐久性。这些发现意味着，对于给定百分比的非 Bt 玉米，玉米种子和其他采耳害虫对多毒素 Bt 玉米的抗性可能比块状种子混合物进化得更快。