Department of Entomology, University of Arizona, Tucson, USA.
MGK, Minneapolis, USA.
Pest Manag Sci. 2018 Nov;74(11):2496-2503. doi: 10.1002/ps.4928. Epub 2018 May 25.
To improve resistance management strategies for Bacillus thuringiensis (Bt) crops, a better understanding of the relative fitness of pest genotypes with resistance alleles in the absence of Bt toxins is needed. Here, we evaluated the impact of costs of resistance to Bt toxin Cry1Ac on the relative fitness of specific pink bollworm (Pectinophora gossypiella) genotypes. We created two heterogeneous strains with an intermediate frequency of mutant cadherin alleles linked with resistance to Cry1Ac, reared the strains on diet without Bt and tracked the decline in frequency of resistant genotypes for 15-30 generations using polymerase chain reaction amplification. We used a population genetics model and sensitivity analyses to estimate the relative fitness of resistant genotypes.
Costs were completely recessive in one strain and almost completely recessive in the other. Estimates of the decline in relative fitness of the resistant homozygotes fed on a diet without Bt were 14-22% in one strain and 21-36% in the other.
Our genotype-specific cost estimates and the results of studies discussed herein indicate that costs associated with resistance to Bt are often large enough to significantly delay the evolution of resistance to pyramided Bt crops in pests with recessive inheritance of resistance. © 2018 Society of Chemical Industry.
为了改进苏云金芽孢杆菌（Bt）作物的抗性管理策略，需要更好地了解具有抗性等位基因的害虫基因型在没有 Bt 毒素的情况下的相对适应性。在这里，我们评估了对 Bt 毒素 Cry1Ac 的抗性成本对特定粉红棉铃虫（Pectinophora gossypiella）基因型相对适应性的影响。我们创建了两个具有中间频率突变钙粘蛋白等位基因的异质菌株，这些等位基因与 Cry1Ac 抗性有关，在不含 Bt 的饮食中饲养这些菌株，并使用聚合酶链反应（PCR）扩增追踪 15-30 代抗性基因型频率的下降。我们使用种群遗传学模型和敏感性分析来估计抗性基因型的相对适应性。
在一个菌株中，成本是完全隐性的，在另一个菌株中几乎完全是隐性的。在一个菌株中，不喂食含 Bt 的饮食时，抗性纯合子相对适应性下降的估计值为 14-22%，而在另一个菌株中则为 21-36%。
我们的基因型特异性成本估计值以及本文讨论的研究结果表明，与 Bt 抗性相关的成本通常足够大，足以显著延迟具有隐性抗性遗传的害虫对 Bt 基因叠加作物的抗性进化。© 2018 化学工业协会。
