Knockdown in the expression of CYP6BQ9 in T. castaneum QTC279 strain reduced its resistance to deltamethrin. (A) The mRNA levels of CYP6BQ9 were quantified by qRT-PCR at 5 days after dsRNA injection. The relative mRNA levels were shown as a ratio in comparison with the levels of rp49 mRNA. The data shown are mean + SEM (n = 3). Statistical significance of the gene expression between two samples was calculated using Student's t test. **P < 0.01. (B) Dose-response curves (log dose versus mortality on a probit scale) for T. castaneum adults exposed to deltamethrin. Bioassays were performed 5 days after dsRNA injection. Lab-S (○◯), a susceptible strain; QTC279 (▽), a deltamethrin resistant strain; QTC279-CYP6BQ9 RNAi (●), QTC279 strain injected with CYP6BQ9 dsRNA; and QTC279-malE RNAi (▼), QTC279 strain injected with malE dsRNA as a control were exposed to various doses of deltamethrin, and the mortality was recorded and graphed.