School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
J Invertebr Pathol. 2012 Jan;109(1):110-6. doi: 10.1016/j.jip.2011.10.005. Epub 2011 Oct 15.
The susceptibility of one of the most important pests in southern Africa, Helicoverpa armigera (Lepidoptera: Noctuidae), to Bacillus thuringiensis Cry proteins was evaluated by bioassay. Cry proteins were produced in Escherichia coli BL21 cells that were transformed with plasmids containing one of six cry genes. The toxicity of each Cry protein to H. armigera larvae was determined by the diet contamination method for second instar larvae and the droplet feeding method for neonate larvae. For each of the proteins, dose-mortality and dose-growth inhibition responses were analyzed and the median lethal dose (LD(50)) and median inhibitory dose (ID(50)) determined. Second instar larvae were consistently less susceptible to the evaluated Cry proteins than neonate larvae. The relative toxicity of Cry proteins ranked differently between neonate larvae and second instar larvae. On the basis of the LD(50) and ID(50) values, Cry1Ab, Cry1Ac, and Cry2Aa were the most toxic of the evaluated proteins to H. armigera larvae. The study provides an initial benchmark of the toxicity of individual Cry proteins to H. armigera in South Africa.
本研究通过生物测定评估了南非最重要害虫之一——棉铃虫（鳞翅目：夜蛾科）对苏云金芽孢杆菌 Cry 蛋白的敏感性。Cry 蛋白在携带 6 种 Cry 基因之一的质粒转化的大肠杆菌 BL21 细胞中产生。用含毒饲料法测定 Cry 蛋白对二龄幼虫的毒性，用点滴法测定对初孵幼虫的毒性。分析了每种 Cry 蛋白的剂量-死亡率和剂量-生长抑制反应，并确定了半数致死剂量（LD50）和半数抑制剂量（ID50）。二龄幼虫对评价的 Cry 蛋白的敏感性明显低于初孵幼虫。Cry 蛋白对初孵幼虫和二龄幼虫的相对毒性排名不同。根据 LD50 和 ID50 值，Cry1Ab、Cry1Ac 和 Cry2Aa 对棉铃虫幼虫的毒性最强。该研究为南非评估 Cry 蛋白对棉铃虫幼虫的毒性提供了初步基准。
