Tabashnik B E, Liu Y B, Finson N, Masson L, Heckel D G
Department of Entomology, University of Hawaii, Honolulu 96822, USA.
Proc Natl Acad Sci U S A. 1997 Mar 4;94(5):1640-4. doi: 10.1073/pnas.94.5.1640.
Environmentally benign insecticides derived from the soil bacterium Bacillus thuringiensis (Bt) are the most widely used biopesticides, but their success will be short-lived if pests quickly adapt to them. The risk of evolution of resistance by pests has increased, because transgenic crops producing insecticidal proteins from Bt are being grown commercially. Efforts to delay resistance with two or more Bt toxins assume that independent mutations are required to counter each toxin. Moreover, it generally is assumed that resistance alleles are rare in susceptible populations. We tested these assumptions by conducting single-pair crosses with diamondback moth (Plutella xylostella), the first insect known to have evolved resistance to Bt in open field populations. An autosomal recessive gene conferred extremely high resistance to four Bt toxins (Cry1Aa, Cry1Ab, Cry1Ac, and Cry1F). The finding that 21% of the individuals from a susceptible strain were heterozygous for the multiple-toxin resistance gene implies that the resistance allele frequency was 10 times higher than the most widely cited estimate of the upper limit for the initial frequency of resistance alleles in susceptible populations. These findings suggest that pests may evolve resistance to some groups of toxins much faster than previously expected.
源自土壤细菌苏云金芽孢杆菌（Bt）的环境友好型杀虫剂是使用最广泛的生物杀虫剂，但如果害虫迅速适应它们，其成功将是短暂的。由于商业化种植产生Bt杀虫蛋白的转基因作物，害虫产生抗性进化的风险增加了。用两种或更多种Bt毒素来延缓抗性的努力假定对抗每种毒素都需要独立的突变。此外，通常认为抗性等位基因在敏感种群中是罕见的。我们通过与小菜蛾（Plutella xylostella）进行单对杂交试验来检验这些假设，小菜蛾是已知在野外种群中首次对Bt产生抗性的昆虫。一个常染色体隐性基因赋予了对四种Bt毒素（Cry1Aa、Cry1Ab、Cry1Ac和Cry1F）极高的抗性。来自一个敏感品系的个体中有21%对多毒素抗性基因是杂合的这一发现意味着抗性等位基因频率比最广泛引用的敏感种群中抗性等位基因初始频率上限估计值高10倍。这些发现表明，害虫对某些毒素组产生抗性的速度可能比之前预期的要快得多。
