小菜蛾Btk抗性品系对四种Bt杀虫晶体蛋白抗性发展的研究

使用苏云金芽胞杆菌库斯塔克亚种（Btk）可湿性粉剂对小菜蛾进行继代汰选获得F80代和F100代抗性品系。通过分别测定Cry1Ab、Cry1Ac、Cry1Ah和Cry1Ca四种杀虫晶体蛋白对小菜蛾Btk抗性品系F80代和F100代的室内毒力，明确了小菜蛾Btk抗性品系对四种Bt杀虫晶体蛋白抗性发展规律。研究结果表明，汰选至F80代时，Cry1Ca对小菜蛾的毒力最高，LC50约12.1mg/L，其次为Cry1Ac,LC50约47.7mg/L；而汰选至F100代时，仍以Cry1Ca对小菜蛾的毒力最高，LC50约21.4 mg/L，其次为Cry1Ab,LC50约72.2 mg/L。与相对敏感品系相比，小菜蛾抗性品系对Cry1Ac的抗性发展较快（抗性倍数高达67.3～106.8倍），对Cry1Ab的次之（抗性倍数高达60.0～66.1倍），而对Cry1Ca和Cry1Ah的抗性发展较慢（抗性倍数分别为3.4～6.0倍和1.6～2.5倍）。以上结果说明，在主效杀虫基因为Cry1Ac的Btk药剂选择压力下，小菜蛾对四种Bt杀虫晶体蛋白的抗性发展速度差异较大，且Cry1Ac和Cry1Ab存在交互抗性风险...

Resistance Development of Four Bt Insecticidal Crystal Proteins against Btk-resistant Strain of Plutella xylostella in the Laboratory

The Bacillus thuringiensis (Bt)-resistant strains of Plutella xylostella (L.) were selected using a wettable powder formulation of Bt var. kurstaki (Btk) for 80 and 100 generations in the laboratory, respectively. The toxicities of four Bt-insecticidal crystal proteins (Cry1Ab, Cry1Ac, Cry1Ah, and Cry1Ca) against Btk-resistant and -susceptible strains of P. xylostella were determined using a standard leaf-dipping method. For the F₈₀ generation of Btk-resistant strain, Cry1Ca had higher toxicity with a LC₅₀value about 12.1 mg/Lthan the other three Cry proteins, followed by Cry1Ac with a LC₅₀value about 47.7 mg/L. For the F₁₀₀ generation of Btk-resistant strain, Cry1Ca still showed higher toxicity with a LC₅₀ value about 21.4 mg/Lthan the other three Cry proteins, followed by Cry1Ab with a LC₅₀ value about 72.2 mg/L. The Btk-resistant strains of P. xylostella showed quick development of resistance to Cry1Ac, with a resistance ratio (RR) increased from 67.3-fold to 106.8-fold when compared with the susceptible laboratory strain. The resistance to Cry1Ab was relatively low, with a RR value from 60.0-fold to 66.1-fold, and the resistance to Cry1Ca and Cry1Ah was even lower, with RR values of 3.4—6.0-fold and 1.6—2.5-fold, respectively. In conclusion, these results suggest that, under the selection pressure of Btk with a dominant gene of Cry1Ac, P. xylostella strains show significant differences in the development of resistance to four insecticidal crystal proteins, and that there is a potential risk of cross-resistance between Cry1Ac and Cry1Ab.