关键词: 甜菜夜蛾, 　氯氟氰菊酯, 　抗药性, 　相对适合度, 　生化机理, 　遗传

Abstract: Comparison of the relative fitness of lambda-cyhalothrin resistant and susceptible strains of the beet armyworm, Spodoptera exigua (Hübner), indicated that the resistant strain possessed reproductive and developmental disadvantages, including lower pupation and oviposition rates, prolonged larval period and lighter weight. The biochemical mechanism of resistance to lambda-cyhalothrin was investigated using enzyme synergists (PBO, SV₁, DEF and DEM) and enzymatic activity assays of esterase, glutathione S-transferase and microsomal O-demethylase. The synergistic ratios of PBO, SV₁, DEF and DEM were 14.1, 14.8, 2.3 and 2.3 folds between resistant and susceptible strains respectively. Synergism to lambda-cyhalothrin by PBO and SV1 was the most distinct. This implied that mixed-function oxidase was involved in the resistance to lambda-cyhalothrin. The ratios of the enzymatic activity of esterase, glutathione S-transferase and microsomal O-demethylase in resistant and susceptible strains were 1.05, 0.91 and 1.05 folds, respectively. These results indicate that detoxification enzymes such as esterase, glutathione S-transferase and microsomal O-demethylase contribute little to the resistance of the beet armyworm to lambda-cyhalothrin. The results of genetic analysis indicated that lambda-cyhalothrin resistance in the beet armyworm appears to be controlled by two or more autosomal genes. The dominance degrees (D) of the F1 progenies from the reciprocal crosses (F₁, R_♀×S_♂ and F’1, R_♂×S_♀) were 0.61 and 0.43, respectively, and the major gene(s) involved is incompletely dominant. The resistant strain possessed 0.61 of the fitness value relative to the isogenic susceptible strain.

Key words: Spodoptera exigua;lambda_cyhalothrin, insecticid e resistance, relative fitness, biochemical mechanism, genetics