Abstract
After eight generations of laboratory selection with β-cypermethrin, a P. okadai strain was cultivated that displayed a 10.04-fold increase in resistance (RS) relative to the susceptible strain (SS), with an estimation of heritability (h(2)) of 0.34. Compared with the SS, the developmental duration of the eggs was significantly prolonged (p < 0.05); however, the pupal stage duration was shorter, with no statistically significant difference. Moreover, the levels of GSTs, CarEs, and CYP450 activity were notably higher in the RS than in the SS. In addition, the level of CarE and CYP450 activity in the RS was significantly higher in the midgut (MG), fat body (FB), and Malpighian tubules (MTs) compared to the SS; however, the GSTs showed no statistically significant difference in the MTs. These results suggest that P. okadai's resistance to β-cypermethrin could be selected rapidly and the decreases in the intrinsic rate of increase (r) observed in the RS are likely due to mutations in the detoxification enzyme genes under the strong selection pressure exerted by β-cypermethrin. The increased activity of GSTs, CarEs, and CYP450 was associated with β-cypermethrin resistance in the RS of P. okadai. The data reported herein provide a foundation for future studies on the mechanisms responsible for β-cypermethrin resistance in P. okadai.