State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, PR China.
J Invertebr Pathol. 2010 Sep;105(1):11-5. doi: 10.1016/j.jip.2010.05.002. Epub 2010 May 7.
Transgenic rice to control stem borer damage is under development in China. To assess the potential of Bacillus thuringiensis (Bt) transgenes in stem borer control, the toxicity of five Bt protoxins (Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1Ca) against two rice stem borers, Sesamia inferens (pink stem borer) and Chilo suppressalis (striped stem borer), was evaluated in the laboratory by feeding neonate larvae on artificial diets containing Bt protoxins. The results indicated that Cry1Ca exhibited the highest level of toxicity to both stem borers, with an LC(50) of 0.24 and 0.30 microg/g for C. suppressalis and S. inferens, respectively. However, S. inferens was 4-fold lower in susceptibility to Cry1Aa, and 6- and 47-fold less susceptible to Cry1Ab and Cry1Ba, respectively, compared to C. suppressalis. To evaluate interactions among Bt protoxins in stem borer larvae, toxicity assays were performed with mixtures of Cry1Aa/Cry1Ab, Cry1Aa/Cry1Ca, Cry1Ac/Cry1Ca, Cry1Ac/Cry1Ba, Cry1Ab/Cry1Ac, Cry1Ab/Cry1Ba, and Cry1Ab/Cry1Ca at 1:1 (w/w) ratios. All protoxin mixtures demonstrated significant synergistic toxicity activity against C. suppressalis, with values of 1.6- to 11-fold higher toxicity than the theoretical additive effect. Surprisingly, all but one of the Bt protoxin mixtures were antagonistic in toxicity to S. inferens. In mortality-time response experiments, S. inferens demonstrated increased tolerance to Cry1Ab and Cry1Ac compared to C. suppressalis when treated with low or high protoxin concentrations. The data indicate the utility of Cry1Ca protoxin and a Cry1Ac/Cry1Ca mixture to control both stem borer populations.
中国正在开发一种用于防治水稻螟虫的转基因水稻。为了评估苏云金芽孢杆菌（Bt）转基因在螟虫防治中的潜力，在实验室中，用含有 Bt 原毒素的人工饲料喂养螟虫幼虫，评估了五种 Bt 原毒素（Cry1Aa、Cry1Ab、Cry1Ac、Cry1Ba 和 Cry1Ca）对两种水稻螟虫（二化螟和稻纵卷叶螟）的毒性。结果表明，Cry1Ca 对两种螟虫的毒性最高，对稻纵卷叶螟和二化螟的 LC50 分别为 0.24 和 0.30μg/g。然而，二化螟对 Cry1Aa 的敏感性比稻纵卷叶螟低 4 倍，对 Cry1Ab 和 Cry1Ba 的敏感性分别低 6 倍和 47 倍。为了评估 Bt 原毒素在螟虫幼虫中的相互作用，用 Cry1Aa/Cry1Ab、Cry1Aa/Cry1Ca、Cry1Ac/Cry1Ca、Cry1Ac/Cry1Ba、Cry1Ab/Cry1Ac、Cry1Ab/Cry1Ba 和 Cry1Ab/Cry1Ca 以 1:1（w/w）的比例进行了混合物的毒性测定。所有原毒素混合物对稻纵卷叶螟均表现出显著的增效毒性活性，毒性比理论加和效应高 1.6-11 倍。令人惊讶的是，除了一种之外，所有的 Bt 原毒素混合物对二化螟的毒性都是拮抗的。在死亡率-时间反应实验中，与稻纵卷叶螟相比，用低浓度或高浓度原毒素处理时，二化螟对 Cry1Ab 和 Cry1Ac 的耐受性增加。数据表明 Cry1Ca 原毒素和 Cry1Ac/Cry1Ca 混合物可用于控制这两种螟虫种群。
