Department of Entomology, University of California-Riverside, Riverside, CA 92521, USA.
J Med Entomol. 2012 Jul;49(4):886-94. doi: 10.1603/me11192.
Mendelian crosses were used to study the mode of inheritance of Cry toxin resistance in a Culex quinquefasciatus Say (Diptera: Culicidae) colony (CqAB11A) that evolved insecticide resistance under laboratory selection with a deletion mutant of Bacillus thuringiensis subsp. israelensis de Barjac lacking the Cyt1Aa toxin component but containing its three major Cry toxins, Cry4Aa, Cry4Ba, and Cry11Aa. High levels of resistance were observed to Cry toxins. F1 offspring of reciprocal crosses to a sensitive colony showed intermediate levels of resistance with no maternal effect, indicating autosomal inheritance. Dose-response data for backcross offspring deviated significantly from the monofactorial model when tested with Cry4Aa + Cry4Ba + Cry11Aa, Cry4Aa + Cry4Ba, or Cry11Aa. However, tests with Cry11Ba from B. thuringiensis subsp. jegathesan (Seleena, Lee, Lecadet) fit the monofactorial model. Dominance of F1 offspring was calculated at different concentrations of Cry-toxin suspensions and, as reported for other Cry-resistant Culex, generally decreased as concentration increased. A subset of colony CqAB11A was reared without selection pressure for 18 generations with little change in susceptibility, indicating a highly homozygous population. Consistent with reports for other Cry-resistant Culex, the data show these mosquitoes evolved resistance to B. thuringiensis Cry toxins at multiple loci in response to selection pressure and that cross-resistance to Cry11Ba was conferred by one of those loci.
孟德尔杂交被用于研究在一个经过实验室选择产生抗药性的库蚊（Culex quinquefasciatus Say）（双翅目：库蚊科）群体（CqAB11A）中，Cry 毒素抗性的遗传模式。该群体对苏云金芽孢杆菌亚种 israelensis 的缺失突变体 Barjac 进行了选择，该突变体缺乏 Cyt1Aa 毒素成分，但含有其三种主要的 Cry 毒素，Cry4Aa、Cry4Ba 和 Cry11Aa。观察到对 Cry 毒素的高水平抗性。与敏感群体进行的正反交 F1 后代表现出中间水平的抗性，没有母体效应，表明是常染色体遗传。当用 Cry4Aa + Cry4Ba + Cry11Aa、Cry4Aa + Cry4Ba 或 Cry11Aa 进行回交后代的剂量反应数据测试时，与单因子模型显著偏离。然而，用苏云金芽孢杆菌亚种 jegathesan（Seleena、Lee、Lecadet）的 Cry11Ba 进行的测试符合单因子模型。F1 后代的显性程度在不同浓度的 Cry-毒素悬浮液中进行计算，与其他抗 Cry 的库蚊报告的情况一样，通常随着浓度的增加而降低。群体 CqAB11A 的一部分在没有选择压力的情况下被饲养了 18 代，对敏感性几乎没有变化，表明这是一个高度纯合的种群。与其他抗 Cry 的库蚊的报告一致，这些数据表明这些蚊子在多个基因座上对苏云金芽孢杆菌 Cry 毒素产生了抗性，以应对选择压力，并且对 Cry11Ba 的交叉抗性是由其中一个基因座赋予的。
