Chlorantraniliprole, an anthranilic diamide insecticide, is widely used for controlling lepidopteran pests, because of its high insecticidal activity. However, overuse of chlorantraniliprole has led to the selection of resistance in many insect pests, including Chilo suppressalis (Lepidoptera:Crambidae), one of the most damaging rice pests in China. In this study, resistance levels to chlorantraniliprole for C. suppressalis was surveyed from eight populations of three provinces in China. The levels of resistance were ranged from 34.4-fold to 284.0-fold compared with a susceptible population. Then, a 15402 bp fragment of the full-length cDNA of ryanodine receptor gene (CsRyR) from the XS strain, the highest resistant population, and a 1992 bp fragment of CsRyR cDNA encoding the carboxyl-terminal of CsRyR gene from the other seven populations were sequenced. A common previously identified mutation that was associated with chlorantraniliprole resistance against C. suppressalis, G4910E, was not detected in any of the eight populations in this study. However, another mutation I4758M was found in all seven resistant populations. Furthermore, the relative mRNA expression levels of CsRyR gene in the seven resistant populations were all reduced compared with susceptible strain. Our study provides new insights into the basis of monitoring the development of resistance and the mechanism of resistance to chlorantraniliprole in C. suppressalis.

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