Data from: Resistance to Bacillus thuringiensis toxin Cry2Ab and survival on single-toxin and pyramided cotton in cotton bollworm from China

Evolution of Helicoverpa armigera resistance to Bacillus thuringiensis (Bt) cotton producing Cry1Ac is progressing in northern China and replacement of Cry1Ac cotton by pyramided Bt cotton has been considered to counter such resistance. Here, we investigated four of the eight conditions underlying success of the refuge strategy for delaying resistance to Cry1Ac+Cry2Ab cotton, a pyramid that has been used extensively against H. armigera outside China. Laboratory bioassays of a Cry2Ab-selected strain (An2Ab) and a related unselected strain (An) reveal that resistance to Cry2Ab (130-fold) was nearly dominant, autosomally inherited, and controlled by more than 1 locus. Strong cross-resistance occurred between Cry2Ab and Cry2Aa (81-fold). Weaker cross-resistance (18- to 22-fold) between Cry2Ab and Cry1A toxins was also present and significantly increased survival of An2Ab relative to An on cotton cultivars producing the fusion protein Cry1Ac/Cry1Ab or Cry1Ac. Survival on Cry1Ac+Cry2Ab cotton was also significantly higher in An2Ab than An, showing that redundant killing on this pyramid was incomplete. Survival on non-Bt cotton did not differ significantly between An2Ab and An, indicating an absence of fitness costs affecting this trait. These results indicate that a switch to three-toxin pyramided cotton could be valuable for increasing durability of Bt cotton in China.中国北方地区棉铃虫（Helicoverpa armigera）对表达Cry1Ac蛋白的苏云金芽孢杆菌（Bacillus thuringiensis，Bt）转Bt基因棉花的抗性演化仍在持续，而通过种植双价转Bt基因棉花（pyramided Bt cotton）替换单价Cry1Ac棉花被认为是应对该抗性问题的有效手段。本研究针对旨在延缓棉铃虫对Cry1Ac+Cry2Ab双价转Bt棉花抗性的庇护所策略（refuge strategy）成功所需的8项前提条件中的4项展开了调查；该双价棉花已在我国以外地区被广泛用于防控棉铃虫。通过对Cry2Ab抗性筛选品系（An2Ab）及其对应的未筛选品系（An）开展室内生物测定（Laboratory bioassays），结果显示：棉铃虫对Cry2Ab的抗性（抗性倍数达130倍）近乎显性且呈常染色体遗传，其抗性由至少2个基因座（locus）控制。Cry2Ab与Cry2Aa之间存在极强的交互抗性（cross-resistance）（抗性倍数为81倍）；此外，Cry2Ab与Cry1A类毒素间也存在较弱的交互抗性（18~22倍），这使得An2Ab品系在表达融合蛋白（fusion protein）Cry1Ac/Cry1Ab或Cry1Ac的棉花品种上的存活率显著高于An品系。An2Ab品系在表达Cry1Ac+Cry2Ab的双价棉花上的存活率同样显著高于An品系，表明该双价棉花的冗余杀虫作用并不完全。An2Ab品系与An品系在非转Bt棉花上的存活率无显著差异，说明该抗性并未伴随影响该性状的适合度代价（fitness costs）。上述结果表明，切换种植三价转Bt基因棉花，或可有效提升我国转Bt基因棉花的抗性持效性（durability）。