抗性小菜蛾的乙酰胆碱酯酶敏感性

ACETYLCHOLINESTERASE SENSITIVITY IN RESISTANT PLUTELLA XYLOSTELLA (L.)

用FAO推荐的点滴法测定了小菜蛾Plutella xylostella(Linn.)对马拉硫磷和西维因的抗药性,并对抗性(R)和敏感(S)小菜蛾幼虫的胆碱酯酶(ChE)的性质、活性、动力学和抑制作用进行了研究。广州天河、上海梅陇的小菜蛾对马拉硫磷的抗性分别是江西南昌种群的113.8和27.4倍;它们对西维因的抗性是》3.1倍。R幼虫ChE对乙酰胆碱(ATCh)、丙酰胆碱(PrTCh)和丁酰胆碱(BuTCh)的活性分别是S幼虫的0.3、0.7和9.9倍;它们的V_(max)分别是0.4、1.4和7.0倍;K_m分别是209.1,87和37.8倍。毒扁豆碱、西维因、对氧磷、敌敌畏和残杀威对R幼虫AChE的抑制中浓度1_(50),分别是S幼虫的333.3,66.7,17.2,12.5和10.0倍。对氧磷、敌敌畏、残杀威和西维因对R幼虫的双分子速率常数K_1,分别是S幼虫的126.4,86.5,32.9和12.3倍。由此可见,AChE敏感度降低是小菜蛾对有机磷和氨基甲酸酯产生抗性的主要机理之一。本文中还讨论了防治抗性小菜蛾的策略。

Larvae of the diamondback moth, Plutella xylostella (II.), from different geographical regions were tested for their resistance to malathion and carbaryl, using topical application recommended by FAO. The Shanghai and Guangzhou populations were found to be 27.4 and 113.8 fold more resistant for malathion and 3.1 fold more resistant for carbaryl than the Nanchang population. Acetylcholinesterase (AchE) activities of the larvae from Shanghai (R) and from Nanchang (S) were examined to know whether their insensitivity in AchE contributed to insecticide resistance, The relative activities of cholinesterase of R and S populations toward acetylthiocholine, propionylthiocholine and butyrylthiocholine were 0.3, 0.7 and 6.8 fold respectively. The kinetic parameters, Vmax and Km, were also determined with the three substrates. Vmax ratios with the S population were 0.4, 1.4 and 7.0, and Km ratios were 201.9, 87.0 and 37.8, tespectively. It is shown that there is a qualitative difference in the AchE between the R and S popultuions . In order ro further confirm the diffetence in inseusitiviry of AchE to inhibition, I50 and the bimolecular rate constant Ki were measured in the B and S popula tions. The I50 ratios of R to S populations was 333.0 for eserine, 66.7 for carbaryl, 17.2 for paraoxon, 32.5 for DDVP and 10.0 for propoxur, and the Ki ratios of insensitivity of AchE to paraoxon, DDVP, propoxur and carbaryl were 126.4, 86.5, 32.9 and 12.3, respectively. It is concluded that resistance to OPs and carbamates in larvae of R populations is associated with a mutant form of AchE of broad insensitivity. Resistance management strategy of the diamondback moth is discussed.