Comparison of carboxylesterase acitivity between the resistant and susceptible strains of Tribolium castaneum to phosphine

The specific activity of carboxlesterase from the resistant(with 327 resistance factor) and susceptible strain of Tribolium castaneum(Herbst) to phosphine was measured comparatively.Frequency distributing of the specific activity of the enzyme for both strains was analyzed further.The special activity of fumigated and unfumigated insects was also determined for the comparison,with different concentration of phosphine in 24 h and different exposure time at concentration of 6.94×10-2 mg/L phosphine.The results showed the specific activity of carboxlesterase in larvae and pupae of resistant strain was 1.73 and 1.16 times higher than that of susceptible one for larvae and 1.16 times higher than that of susceptible strain,respectively.There was a significant difference in the frequency distribution of the specific enzyme activity between two strains in which the frequency of insect individuals with higher specific activity in resistant strain was more than that of susceptible insects.The specific enzyme activity from susceptible strain was decreased after 24 h fumigation at tested concentration of 0.69×10-2,2.78×10-2,5.56×10-2,8.33×10-2 and 11.11×10-2 mg/L apart,and that from resistance was increased after the fumigation with concentration of 5.56×10-2、11.11×10-2、13.89×10-2 、20.83×10-2 and 27.78×10-2 mg/L.The specific enzyme activity in susceptible strain was decreased and that of resistance strain was increased with the exposure time going on at the concentration 6.94×10-2 mg/L of phosphine.It revealed that the resistance to phosphine might be related to the activity of carboxlesterase in red flour beetle.