Biochemical basis of resistance in laboratory selected fenazaquin resistant strain of Two-spotted spider mite, Tetranychus urticae Koch

The Two-spotted spider mite, Tetranychus urticae Koch is a serious pest in many cropping systems worldwide including fruits, vegetables and ornamental plants in both closed and open area. T. urticae has developed resistance against different groups of acaricides and no biochemical studies have been conducted to assess the basis/mechanisms of acaricide resistance in T. urticae populations of North India. Therefore, mechanism of acaricide resistance in T. urticae through enzyme assays was investigated. Field population of T. urticae showing resistance to fenazaquin (24.65 fold) was selected with fenazaquin successively for 15 generations to develop fenazaquin resistant strain leading to 6.83 fold increase in the resistance level. There was significant increase in specific activity of the MFO enzymes in resistant strain (534.65 nmol of p-nitrophenol formed min(-1) mg(-1) of protein) as compared to susceptible strain (166.35 nmol of p-nitrophenol formed min(-1) mg(-1) of protein). There was 3.21 fold higher MFO activity in resistant strain. Similarly, there was significant increase in GST activity by 1.40 fold and esterase activity by 1.13 and 1.27 fold with alpha-naphthyl acetate and beta-naphthyl acetate as substrate in resistant population. The biochemical experiments conducted in the present study suggested that enhanced metabolic detoxification might be the major mechanism responsible for imparting resistance to fenazaquin in T. urticae.