二化螟对杀螟硫磷产生抗性的机理

本文就二化螟Ckilo suppressalis Walker对杀螟硫磷抗性发生的机理进行了较为全面的研究。活体增效作用研究表明，脱叶磷(DEF)和氧化胡椒基丁醚(PBO)对抗性种群可分别增效1.3和34.8倍。这表明了多功能氧化酶(MFO)活性增强，而似乎与水解酶的活性无关。对寓体解毒酶的进一步研究表明，抗性和敏感种群的非特异性酯酶活力无明显差异，但羧酸酮酶(CarE，加入10^-4mol/L的毒扁豆碱)和MFO的活力在抗性种群中有所增高。R种群幼虫CarE活力分别是s的2.42和2.92倍(以a-和β-乙酸萘酯为底物)；R种群幼虫MFO的O-脱甲基作用的活力为s幼虫的1.43倍(以对硝基茴香醚为底物)；R幼虫乙酰胆碱酯酶(AChE)对乙酰胆碱的活力是s的1.3倍，两者相差不大。但从米氏常数K_m)和最大反应速度(V_max)看，R幼虫是s幼虫的1.9和1.6倍；以对氧磷为抑制剂的R幼虫150是s幼虫的2倍。这些表明了R和s的AChE是不同的。研究结果还表明，二化螟对杀螟硫磷抗性的机理至少包括：(1)CarE活性的增高；(2)MFO的O-脱甲基活力的增高和(3)AChE敏感性的降低等。

THE MECHANISM OF RESISTANCE TO FENITROTHIONIN THE RICE STEM BORER CHILO SUPPRES. SALIS WALKER

The mechanism of resistance to fenitrothion in the rice stem borerChilo suppressalit Walker is comprehensively investigated. Resistant strain ?, initiated from a field population, was selected successively by fenitrothion to the 7th generation and the resistant ratio was 14.1 as compared with that of the susceptible strain (S), which was obtained by selection with single-egg mass method. Synergism experiments showed that the synergistic ratio of DEF and PBO to fenitrothion in R strain were 1.3X and 34.8X, respectively. It suggested that resistance to fenitrothion was partially associated with multiple function oxidase (MFO). Furthermore, the activities of non-specific esterase, carboxylesterase (CarE) and MFO were determined in vitro. The results indicated that the activities of non-specific esterase in R and S strains showed no significant difference when using substrates of a-naphthyl acetate and β-naphthyl acetate. But there was difference in the activity to Care between R and S strains. The activities of Care from the larvae of R strainwith above-mentioned substrates (with 10^-4 esterin) were 2.42-and 2.92-fold higher than that of S strain, respectively. The ratio of 0-demethylation activities of MFO extracts from R strain to that of S strain was found to be 1.43. The acetylcholinesterase (ACHE) activities and the kinetic parameter, K_m and I₅₀ of paraoxon were also measured. The ratios of activities, K_m and I₅₀ of R strain to that of S strain were 1.6, 1.7 and 2.0, respectively. It was apparent that the Ache in R strain have altered. From the results obtained, it is concluded that the onset of resistance to fenitrothion in the rice stem borer is due to multi-factor including high activities ofCarE, MFO, enhanced O-demethylation of MFO and insensitivities of ACHE.