Enzymatic Resistance in Diamondback Moth, Plutella xylostella (Linneaus)

Total activity of general esterases and acetylcholinesterases for resistant population of Plutella xylostella (Linneaus) was 208.10 μg of α-naphthol produced min⁻¹g⁻¹ fresh weight in resistant population and 142.15 μg of α-naphthol produced min⁻¹g⁻¹ fresh weight for susceptible population. Specific activity of general esterases was also higher in resistant population (4.84 μg of α-naphthol produced min⁻¹mg⁻¹ protein) than in the susceptible population (3.22 μg of α-naphthol produced min⁻¹mg⁻¹ protein). Similar trend was observed in both the populations as regards acetylcholinesterase activity. The total activity of acetylcholinesterases was higher in resistant population i.e. 161.90 n moles min⁻¹ g⁻¹ fresh weight than that shown by susceptible population (137.60 n moles min⁻¹ g⁻¹ fresh weight). In case of specific activity too, similar trend was evident in the resistant and susceptible populations. Resistant population showed higher activity of enzyme acetylcholinesterase i.e. 3.78 n moles min⁻¹ mg⁻¹ protein as compared to 3.19 n moles min⁻¹ mg⁻¹ protein in case of susceptible P. xylostella. The significantly higher values of general esterases and acetylcholinesterases in the resistant larvae provide an opportunity to explore the possibility of using these as biochemical tools to monitor resistance in the pest.