Key Laboratory of Integrated Management of Crop Diseases and Pests Ministry of Education, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
Proc Natl Acad Sci U S A. 2012 Jun 26;109(26):10275-80. doi: 10.1073/pnas.1200156109. Epub 2012 Jun 11.
Evolution of pest resistance reduces the efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays or in transgenic crops. Although several pests have evolved resistance to Bt crops in the field, information about the genetic basis of field-evolved resistance to Bt crops has been limited. In particular, laboratory-selected resistance to Bt toxin Cry1Ac based on recessive mutations in a gene encoding a toxin-binding cadherin protein has been identified in three major cotton pests, but previous work has not determined if such mutations are associated with field-selected resistance to Bt cotton. Here we show that the most common resistance alleles in field populations of cotton bollworm, Helicoverpa armigera, selected with Bt cotton in northern China, had recessive cadherin mutations, including the deletion mutation identified via laboratory selection. However, unlike all previously studied cadherin resistance alleles, one field-selected cadherin resistance allele conferred nonrecessive resistance. We also detected nonrecessive resistance that was not genetically linked with the cadherin locus. In field-selected populations, recessive cadherin alleles accounted for 75-84% of resistance alleles detected. However, most resistance alleles occurred in heterozygotes and 59-94% of resistant individuals carried at least one nonrecessive resistance allele. The results suggest that resistance management strategies must account for diverse resistance alleles in field-selected populations, including nonrecessive alleles.
抗虫性的进化降低了苏云金芽孢杆菌（Bt）杀虫蛋白在喷雾或转基因作物中的功效。尽管几种害虫在田间已经对 Bt 作物产生了抗药性，但关于田间进化对 Bt 作物的抗药性的遗传基础的信息一直有限。特别是，基于编码毒素结合钙粘蛋白蛋白的基因中的隐性突变，在三种主要棉虫中已经鉴定出对 Bt 毒素 Cry1Ac 的实验室选择的抗性，但以前的工作尚未确定这种突变是否与田间选择对 Bt 棉花的抗性有关。在这里，我们表明，在中国北方使用 Bt 棉花选择的棉铃虫田间种群中最常见的抗性等位基因具有隐性钙粘蛋白突变，包括通过实验室选择鉴定的缺失突变。然而，与所有以前研究的钙粘蛋白抗性等位基因不同，一个田间选择的钙粘蛋白抗性等位基因赋予非隐性抗性。我们还检测到与钙粘蛋白基因座没有遗传关联的非隐性抗性。在田间选择的种群中，隐性钙粘蛋白等位基因占检测到的抗性等位基因的 75-84%。然而，大多数抗性等位基因发生在杂合子中，59-94%的抗性个体携带至少一个非隐性抗性等位基因。结果表明，抗性管理策略必须考虑田间选择种群中的多种抗性等位基因，包括非隐性等位基因。
