棉铃虫对氰戊菊酯-辛硫磷混剂的抗性演化及解毒酶活性变化

用氰戊菊酯-辛硫磷混剂（有效成分1∶10，简称氰-辛混剂）对棉铃虫Helicoverpa armigera室内品系(YS)进行16代的抗性选育，获得棉铃虫对氰-辛混剂的抗性品系（YS-FP）。YS-FP品系与YS品系相比，对氰-辛混剂的抗性为14.7倍，对其中的单剂氰戊菊酯和辛硫磷的抗性分别为2 170倍和3.1倍。随着筛选的进行，氰戊菊酯和辛硫磷之间的共毒系数在F₂代出现短暂的增加，然后逐渐降低，它们之间的互作由增效变为拮抗。交互抗性测定结果表明，YS-FP品系对氯氰菊酯、溴氰菊酯、三氟氯氰菊酯、三唑磷和灭多威产生了明显的交互抗性，对硫丹、多杀菌素和爱玛菌素没有产生交互抗性。YS-FP品系6龄幼虫中肠细胞色素P450氧化酶甲氧基香豆素O-脱甲基活性为YS品系的10倍，3龄幼虫谷胱甘肽S-转移酶和酯酶活性分别是YS品系的1.7倍（CDNB结合作用）和2.4倍（α-NA 酯酶水解作用）。氰-辛混剂的筛选导致了棉铃虫多种解毒酶活性的增加，特别是细胞色素P450氧化酶活性增强最为明显。本研究结果表明氰-辛混剂对棉铃虫的筛选导致了广谱的交互抗性和多种代谢抗性机理，并且两个单剂之间的互作由增效变为拮抗，因此氰 辛混剂在棉铃虫抗性治理中的作用是有限的和暂时的。

Resistance evolution and change of detoxification enzyme activity in a strain of Helicoverpa armigera selected with a mixture of fenvalerate and phoxim

The resistant YS-FP strain of Helicoverpa armigera was selected from the susceptible YS strain with a mixture of fenvalerate and phoxim (a.i., 1∶10) for 16 generations. Compared with the YS strain, the YS-FP strain developed 14.7-fold resistance to the mixture itself, 2.170-fold resistance to fenvalerate and 3.1-fold resistance to phoxim. During 16 generations of continuous selection with the mixture, the co toxicity coefficient decreased gradually after a brief increase at F₂, and the interaction between fenvalerate and phoxim against the YS-FP strain changed from synergism to antagonism. The YS-FP strain had significant cross resistance to three pyrethroids (cypermethrin, deltamethrin and cyhalothrin), triazophos and methomyl, but no cross resistance to endosulfan, spinosad and emamectin. The cytochrome P450 oxidase O-demethylation activity in midguts of 6th instar larvae from the YS-FP strain was 10-fold of that from the YS strain; and the glutathione S-transferase activity (CDNB conjugation) and esterase activity (to the substrate α naphthyl acetate) of 3rd instar larvae from the YS-FP strain were 1.7 and 2.4-fold respectively compared with the YS strain. The selection of the fenvalerate and phoxim mixture in the YS strain of H. armigera resulted in broad-spectrum cross resistance, multiple metabolic resistance mechanisms (especially enhanced cytochrome P450 oxidase) and antagonistic effect between fenvalerate and phoxim. The results suggested that the role of such fenvalerate and phoxim mixture in resistance management of H. armigera could be limited and temporary. 