Monitoring of insecticide resistance and transcriptomic analysis of detoxification gene expression in field populations of Diaphorina citri (Hemiptera: Psyllidae) in China.

Diaphorina citri is one of the most destructive pests to global citrus production. Chemical control through insecticide application has traditionally served as the primary intervention strategy for suppressing D. citri populations. However, recent field observations from China have indicated diminishing control efficacy, suggesting potential resistance development. This study assessed insecticide resistance in 10 D. citri field populations from major citrus-producing provinces across the Guangxi-Hunan-Jiangxi region and characterized transcriptomic changes. Bioassays against 6 insecticides revealed variable resistance profiles. Chlorpyrifos resistance ranged from 9- to 16-fold across 9 of 10 populations, with Huichang showing the highest ratio (16-fold). The Ganxian population showed 6.1-fold thiamethoxam, 8.3-fold imidacloprid, and 14-fold chlorpyrifos resistance. Resistance to dinotefuran (0.75 to 3.2-fold), clothianidin (0.47 to 2.2-fold), and lambda-cyhalothrin (0.95 to 4.7-fold) remained low across all populations, as did resistance in the Nanfeng population to all 6 insecticides (RR₅。 = 0.47 to 2.7). Comparative transcriptomic analysis between the resistant Ganxian and minimally resistant Nanfeng populations revealed distinct gene expression profiles. In the Ganxian population, 19 cytochrome P450 genes, 3 glutathione S-transferase genes, and 1 UDP-glycosyltransferase gene were upregulated, and gene ontology enrichment analysis identified significant enrichment of oxidoreductase activity (false discovery rate < 0.05). Quantitative real-time polymerase chain reaction validation across 4 populations confirmed that CYP4C1, GSTT1, and UGT2B9 expression was broadly consistent with resistance phenotypes, though these associations remain correlative pending functional validation. These findings provide region-specific baseline data to support targeted, population-specific resistance management for D. citri in one of China's most important citrus-producing regions.