Abstract: 【Aim】The aim of this study is to investigate the biological function of ABC transporter genes in the development of resistance to indoxacarb in Spodoptera frugiperda, so as to provide a theoretical basis for the comprehensive control of this pest. 【Methods】 Indoxacarb alone and combined with ABC transporter inhibitor verapamil hydrochloride were used to treat the 3rd instar larvae of the indoxacarb-resistant population DC-22 and the indoxacarb-susceptible strain WH of S. frugiperda by the topical application method, and the median lethal concentration (LC₅₀) and the synergistic ratio of verapamil hydrochloride to indoxacarb were calculated at 24 h after treatment. The expression levels of seven ABC transporter genes (SfABCG20, SfABCC2, SfABCF4, SfABCA1, SfABCA5, SfABCG23 and SfABCG9) in the 3rd instar larvae of the indoxacarb-susceptible strain WH and four indoxacarb-resistant populations， including DC-22, CX-22, MY-22 and RH-22, were examined. The highly expressed ABC transporter gene SfABCG23 in response to indoxacarb was silenced through RNAi by injecting dsSfABCG23 into the 3rd instar larvae of DC-22 and WH. The expression level of SfABCG23 was detected by RT-qPCR at 48 h after RNAi, and the mortality was detected at 24 h after exposure to LC₃₀of indoxacarb following RNAi.【Results】Verapamil hydrochloride significantly increased the susceptibility of the indoxacarb-resistant population DC-22 to indoxacarb, with the synergistic ratio of 1.73. The expression levels of SfABCG23 in the 3rd instar larvae of the indoxacarb-resistant populations DC-22 and CX-22 were up-regulated by 2.56- and 4.05-fold, respectively, as compared with that in the indoxacarb-susceptible strain WH, and the expression level of SfABCG23 was significantly positively correlated with the resistance ratio, with the correlation coefficient of 0.941. After dsSfABCG23 injection, the gene silencing efficiency was 65.04% and 39.55%, respectively, in the indoxacarb-resistant population DC-22 and the indoxacarb-susceptible strain WH, and compared with the dsGFP-injected control group, the dsSfABCG23 injection increased the mortality of the 3rd instar larvae of the indoxacarb-resistant population DC-22 and the indoxacarb-susceptible strain WH, by 30.55% and 25.00%, respectively, at 24 h after exposure to indoxacarb. 【Conclusion】 The results of this study suggest that ABC transporter genes play an important role in regulating the development of resistance in the indoxacarb-resistant population of S. frugiperda, and the overexpression of SfABCG23 may play an important role in the development of resistance to indoxacarb in S. frugiperda.

Key words: Spodoptera frugiperda, insecticide resistance, indoxacarb, ABC transporter, verapamil hydrochloride, synergistic effect