Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
Department of Entomology, The University of Arizona, Tucson, AZ, USA.
J Econ Entomol. 2024 Oct 14;117(5):2093-2099. doi: 10.1093/jee/toae194.
The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a significant cotton pest worldwide. Bacillus thuringiensis (Bt) cotton producing Cry1Ac has been used since 1997 for the control of this pest in China and a significant increase in H. armigera resistance to Cry1Ac has occurred in northern China. To mitigate resistance evolution, it is necessary to develop and plant pyramided 2- and 3-toxin Bt cotton to replace Cry1Ac cotton. For sustainable use of pyramided Bt cotton, we used diet overlay bioassays to measure the baseline susceptibility of H. armigera to Cry2Ab in 33 populations collected in 2017, 2018, and 2021 in 12 locations from major cotton-producing areas of China. The lethal concentration killing 50% (LC50) or 99% (LC99) of individuals from the populations ranged from 0.030 to 0.138 µg/cm2 and 0.365 to 2.964 µg/cm2, respectively. The ratio of the LC50 for the most resistant and susceptible population was 4.6, indicating moderate among-population variability in resistance. The susceptibility of H. armigera to Cry2Ab did not vary significantly over years. A diagnostic concentration of 2 µg/cm2 was calculated as twice the LC99 from an analysis of pooled data for the field-collected populations. This concentration discriminated well between susceptible and resistant individuals, as it killed all larvae from a susceptible laboratory strain and 0%, 0%, and 23% of larvae from 3 laboratory strains with > 100-fold resistance to Cry2Ab. These baseline susceptibility data and diagnostic concentration for Cry2Ab will be useful for monitoring the evolution of H. armigera resistance to pyramided Bt cotton in China.
棉铃虫，Helicoverpa armigera（Hübner）（鳞翅目：夜蛾科），是世界范围内重要的棉花害虫。自 1997 年以来，中国一直在使用生产 Cry1Ac 的苏云金芽孢杆菌（Bt）棉花来控制这种害虫，并且在中国北方，棉铃虫对 Cry1Ac 的抗性显著增加。为了减轻抗性的进化，有必要开发和种植含有 2-和 3-毒素的Bt 棉花来替代 Cry1Ac 棉花。为了可持续使用含有多种毒素的 Bt 棉花，我们使用饮食覆盖生物测定法来衡量 2017 年、2018 年和 2021 年从中国主要棉花产区的 12 个地点收集的 33 个种群中棉铃虫对 Cry2Ab 的基础敏感性。种群个体的致死浓度 50%（LC50）或 99%（LC99）范围为 0.030 至 0.138 µg/cm2 和 0.365 至 2.964 µg/cm2。最抗和最敏感种群的 LC50 比值为 4.6，表明种群间抗性存在中等变异性。棉铃虫对 Cry2Ab 的敏感性在过去几年中没有明显变化。根据对田间采集种群的汇总数据进行分析，计算出 2 µg/cm2 的诊断浓度为 LC99 的两倍。该浓度能很好地区分敏感个体和抗性个体，因为它杀死了敏感实验室品系的所有幼虫，以及对 Cry2Ab 具有超过 100 倍抗性的 3 个实验室品系的 0%、0%和 23%的幼虫。这些 Cry2Ab 的基础敏感性数据和诊断浓度将有助于监测中国棉铃虫对含有多种毒素的 Bt 棉花的抗性进化。
