A 96-Well Microplate Reader for Measuring Characterization of Esterase and Insecticide Resistance in the Cotton Aphids (Aphis gossypii Glover)

The bioassay showed that Gaomi cotton aphid had higher resistance to organophosphate insecticides than Beijing cotton aphid. Using two approaches, a conventional spectrophotometer (method A) and a 96-well microplate reader method (method B),to detect general α-naphthyl acetate(α-NA) esterase activity and kinetics of α--NA esterase of Gaomi and Beijing cotton aphid. The α-NA esterase activity of Beijing and Gaomi cotton aphid were 2.23 and 4.48 (method A),1.28 and 3.30 μmol·mg-1 protein·min-1 (method B),respectively; The α-NA esterase activity ratio of G/B were 2.00 and 2.56; Km of α-NA esterase in Beijing and Gaomi cotton aphid were 6.06×10-5 and 7.51×10-5 (method A),7.66×10-5 and 8.87×10-5 (method B) mol·L-1 , respectively; Vmax were 2.53 and 5.82 (method A),1.28 and 3.61(method B) μmol·mg-1 protein·min-1 , respectively. Data obtained from the 96-well microplate reader were compared to those obtained, under similar conditions, in a conventional spectrophotometer. The approach of using the 96-well microplate reader should be generally applicable to monitor pest resistance to insecticide.