Effect of sublethal concentrations of bifenazate on detoxifying enzymes in Tetranychus truncatus
Author of the article:SHANG Su-Qin；XUE Yu-Li
Author's Workplace：College of Plant of Gansu Agricultural University, Biological Engineering Laboratory of Crop Diseases and Pests of Gansu Province, Lanzhou 730070, China；College of Plant of Gansu Agricultural University, Biological Engineering Laboratory of Crop Diseases and Pests of Gansu Province, Lanzhou 730070, China
Key Words：Tetranychus truncatus; bifenazate; lethal concentration; detoxifying enzymes; specific activity; kinetic parameters of enzymology
Abstract：[Objectives] To determine the effect of sublethal concentrations of bifenazate on detoxifying enzymes in Tetranychus truncatus, further understanding of the mechanism underlying resistance to bifenazate in this species and improve the application of bifenazate. [Methods] The LC50 of bifenazate to adult female T. truncatus was tested using the leaf-dipping method and sublethal concentrations corresponding to 10% and 30% mortality (LC10 and LC30) calculated from the virulence regression equation. The specific activity, and two constants of kinetic parameters, Michaelis constant (Km) and Maximal velocity (Vmax), of carboxylesterase (CarE), glutathione s-transferase (GSTs) and multifunctional oxidase (MFO), were tested and analyzed after treating T. truncatus with LC10 and LC30 doses of bifenazate. [Results] Specific activities of CarE, GSTs and MFO were all significantly increased (P<0.05) by exposure to LC10 and LC30 doses of bifenazate. The specific activities of CarE and GSTs in the LC30 treatment group were generally significantly higher than those of the LC10 treatment group (P<0.05). The Km value of CarE either decreased significantly, or had no significant change (P<0.05), whereas that of GSTs and MFO increased significantly, or had no significant change (P<0.05). The Vmax value of CarE increased significantly (P < 0.05), indicating that CarE has a high substrate affinity and catalytic rate. Conversely, the Vmax value of GSTs and MFO decreased significantly (P < 0.05), indicating low substrate affinity. [Conclusion] Bifenazate can induce the activity of detoxification enzymes in T. truncatus and CarE plays a key role in the detoxification of bifenaazate in this species.