Impact of Imidacloprid Resistance on the Demographic Traits and Expressions of Associated Genes in Glover.

Imidacloprid is one of the most widely used neonicotinoid insecticides to control sap-sucking insect pests, including . The intensive application of chemical insecticides to led to the development of resistance against several insecticides, including imidacloprid. Therefore, it is crucial to understand the association between imidacloprid resistance and the fitness of to limit the spread of the resistant population under field contexts. In this study, we used the age-stage, two-sex life table method to comprehensively investigate the fitness of imidacloprid resistant (ImR) and susceptible strains (SS) of melon aphids. Results showed that ImR aphids have prolonged developmental stages and decreased longevity, fecundity, and reproductive days. The key demographic parameters (, , and ) were significantly reduced in ImR strain compared to SS aphids. Additionally, the molecular mechanism for fitness costs was investigated by comparing the expression profile of juvenile hormone-binding protein (), juvenile hormone epoxide hydrolase (, juvenile hormone acid O-methyltransferase (, Vitellogenin (), ecdysone receptor (), and ultraspiracle protein () supposed to be associated with development and reproduction in insects. The results of RT-qPCR showed that , , , and genes were downregulated, while was statistically the same in ImR compared to the SS strain. Together, these results provide in-depth information about the occurrence and magnitude of fitness costs against imidacloprid resistance that could help manage the evolution and spread of resistance in field populations.