| Spodoptera exigua (Hübner) was a polyphagous insect that endangers various agricultural crops, such as vegetables, cotton et al in recent years. Indoxacorb as a novel oxadiazine insecticide has become one of the mainly pesticides against S. exigua instead of conventional chemical medicine. Thus, the validity and management of resistance to S. exigua with indoxacarb would be people's attention in the future. This paper was related to selecting of S. exigua with indoxacarb by leaf dipping method and gaining the resistant S. exigua against indoxacarb (RR-indox).The risk of resistance in S. exigua to indoxacarb was evaluated in the paper. Biological methods were used for confirming the degrees of cross-resistance of 8 other insecticides. The estimated realized heritability (h2) of RR-indox strain was assessed,and the speed of resistance increasing of S. exigua against indoxacarb was calculated. The relative fitness of indoxacarb resistant strain in S. exigua was evaluated by constituting life table of different strains. The inheritance mode of resistance to indoxcarb in S. exigua was evaluated from log dosage-probit mortality curves and statistical methods. In addition, the resistance biochemical mechanism, including the cuticular penetration rate by High Performance Liquid Chromatography(HPLC), synergist by biological assay of PBO, DEM and TPP, activity assay of detoxifying enzymes, and esterase kinetics. The results are as follows.1. After 12 generations selection of the field S. exigua strain by indoxacarb, the resistant strain (RR-indox) was gained with the 240-fold resistance ratio compared with the susceptible strain (SS-WH).2. Resistance strain (RR-indox) showed the moderate cross-resistance level to emamectin benzoate (12.59- fold) and little cross-resistance to other 7 insecticides. No significantly cross-resistance for chlorfennapyr, methomyl, chlorfluazuron, spinosad and beta-cypermethrin, While more sensitive to tebufenozide and chlorpyrifos. The estimated realized heritability (h2) of RR-indox strain was 0.25. The number of generations required for a hundredfold increase in LC50 was estimated to be 9 under the 90% lethal dose. The RR-indox strain has a fitness value of 0.44 relative to the susceptible strain. The results indicated that the RR-indox strain possessed development and reproductive disadvantages. The values of dominance degrees (D) of the F1 progenies (F1, R♀×S♂; F'1, S♀×R♂) from the reciprocal cross were 0.54 and 0.74, respectively. It suggested that the resistance of indoxacarb in S. exigua was autosomal, incompletely dominant and probably polygenic.3. The cuticular penetration rate had no differences between the resistant strain and susceptible strain. The inhibitors, PBO, TPP and DEM had synergistic ratio 0.87-, 0.31- and 0.36-fold for the resistant strain, and 0.51-, 0.09- and 0.12-fold for susceptible strain. The 3.68-fold higher levels activity of glutathione S-transferase was found in RR-indox than in SS-WH, while 1.99-fold of carboxylesterase. The value of Km and Vmax in RR-indox were significantly lower than SS-WH with 0.12-fold and 0.42-fold, respectively. The resistance of indoxacarb in the S. exigua population was associated with glutathione S-transferase mainly, followed by carboxylesterase and as cuticular penetration indirectly.
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