The evolution of resistance to two-toxin pyramid transgenic crops
The evolution of resistance to two-toxin pyramid transgenic crops
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DOI：
10.1890/09-1869.1
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发表时间：
2011-03-01
影响因子：
5
通讯作者：
Andow, David A.
中科院分区：
文献类型：
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作者：
Ives, Anthony R.;Glaum, Paul R.;Andow, David A.
表达两种苏云金芽孢杆菌 (Bt) 毒素的金字塔转基因作物在减少昆虫损害和减缓毒素抗性进化方面具有巨大潜力。在这里，我们分析了一套金字塔 Bt 作物模型，以说明在实施抗性管理高剂量避难策略时应考虑的因素；该策略涉及 Bt 植物中毒素的高表达以及使用非 Bt 植物作为避难所。尽管对金字塔 Bt 品种的抗性进化通常应该较慢，但对金字塔 Bt 品种的抗性仍然是由与单一 Bt 毒素品种相同的进化过程驱动的。金字塔品种的主要优点是抗性等位基因杂合昆虫的存活率较低。我们证明了耐药性进化有两种模式。当纯粹易感昆虫的种群持续存在时，导致密度依赖性，抗性进化的速度随着避难所的比例而缓慢变化。然而，一旦非 Bt 植物的比例超过易感群体无法持续存在的阈值，抗性进化的速度就会迅速增加。这表明适应性管理可用于保证易感人群的持续存在。我们将 Bt 和非 Bt 植物播种在同一田地中的种子混合物的使用与空间避难所的使用进行了比较。正如对单一 Bt 品种的发现，如果幼虫在植物之间移动，种子混合物可以加速抗性进化。制定部署空间避难所的最佳管理计划很困难，因为它们取决于作物轮作模式、雄性或雌性的扩散有限以及其他特征。尽管如此，空间避难所对抗性进化的影响可以通过考虑决定抗性进化速率的三种机制来理解：选择力（被 Bt 杀死的昆虫的比例）、选型交配（总种群水平上杂合子比例偏离 Hardy-Weinberg 平衡）和雄性交配成功（当携带抗性等位基因的雄性发现更少的昆虫时）。 伙伴们）。在这三者中，选型交配通常是最不重要的，尽管这种机制是高剂量避难策略有效性最常被引用的解释。
Pyramid transgenic crops that express two Bacillus thuringiensis (Bt) toxins hold great potential for reducing insect damage and slowing the evolution of resistance to the toxins. Here, we analyzed a suite of models for pyramid Bt crops to illustrate factors that should be considered when implementing the high dose-refuge strategy for resistance management; this strategy involves the high expression of toxins in Bt plants and use of non-Bt plants as refuges. Although resistance evolution to pyramid Bt varieties should in general be slower, resistance to pyramid Bt varieties is nonetheless driven by the same evolutionary processes as single Bt-toxin varieties. The main advantage of pyramid varieties is the low survival of insects heterozygous for resistance alleles. We show that there are two modes of resistance evolution. When populations of purely susceptible insects persist, leading to density dependence, the speed of resistance evolution changes slowly with the proportion of refuges. However, once the proportion of non-Bt plants crosses the threshold below which a susceptible population cannot persist, the speed of resistance evolution increases rapidly. This suggests that adaptive management be used to guarantee persistence of susceptible populations. We compared the use of seed mixtures in which Bt and non-Bt plants are sown in the same fields to the use of spatial refuges. As found for single Bt varieties, seed mixtures can speed resistance evolution if larvae move among plants. Devising optimal management plans for deploying spatial refuges is difficult because they depend on crop rotation patterns, whether males or females have limited dispersal, and other characteristics. Nonetheless, the effects of spatial refuges on resistance evolution can be understood by considering the three mechanisms determining the rate of resistance evolution: the force of selection (the proportion of insects killed by Bt), assortative mating (deviations of the proportion of heterozygotes from Hardy-Weinberg equilibrium at the total population level), and male mating success (when males carrying resistance alleles find fewer mates). Of these three, assortative mating is often the least important, even though this mechanism is the most frequently cited explanation for the efficacy of the high dose-refuge strategy.