Resistance mechanisms to fenazaquin in Iranian populations of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract

Resistance mechanisms to fenazaquin were surveyed in Iranian populations of the two-spotted spider mite, Tetranychus urticae Koch. The bioassay was carried out on four populations, collected from Isfahan, Yazd and Rasht using the leaf-dip method. The results showed that resistance ratios of Isfahan, Yazd and Rasht populations were 3109-, 439.5- and 10.53-fold, respectively, compared with the susceptible population. Enzyme assays revealed that esterase activities in the Isfahan, Yazd and Rasht populations were 3.9-, 1.8- and 1.5-fold higher than that in the susceptible population, respectively, when α-naphthyl acetate was used as the substrate. Glutathione S-transferase (GST) activity in the Isfahan, Yazd and Rasht populations was 2.3-, 2.4- and 1.4-fold higher, respectively, than that in the susceptible one. Zymogram analysis of esterase and GST showed that there was some difference in the pattern of bands between the populations. Also, the activity of lipase in Yazd, Isfahan and Rasht populations was 1.98, 1.68 and 2.84-fold more than that in the susceptible population. Furthermore, the results showed that the amount of cytochrome P₄₅₀ was much higher in Isfahan and Yazd populations than in the susceptible compartment. The bioassay and biochemical results suggested the involvement of three detoxification enzymes, esterase, MFO and GST, in fenazaquin resistance but the role of these enzymes in Isfahan and Yazd populations was low. Due to high resistance ratio in the Isfahan and Yazd populations, in addition to metabolic resistance, it seems the main resistance mechanism to fenazaquin is the insensitivity of the target site.

Keywords:

• Tetranychus urticae
• resistance mechanisms
• esterases
• glutathione S-transferase
• cytochrome P₄₅₀

Acknowledgements

We express our gratitude to the research council of the University of Guilan and Ministry of Science, Researches, and Technology for financial support during the course of this project.