Studies On The Effect Of Two Pesticides On Paratrioza Sinica Yang & Li And Its Carboxylesterase (CarE)

Chinese wolfberry psyllid, Paratrioza sinica Yang & Li, is one of the major pests in the cultivation area of Chinese wolfberry. It causes the decrease in quality and the poor output of Chinese wolfberry, and even harvestless. The toxicity and the inhibitory effect of two pesticides on Carboxylesterase (CarE) in different instars of P. sinica.had been studied.The results as followed:1. The median lethal concentration (LC₅₀) of P. sinica increased with the instars went older in nymph stage, but the adult was opposite. The result showed that triazophos had the highest toxicity in 2nd instar nymph. Its LC₅₀ was 0.012 mg/L, which was 43.25 times compared to that of 5th. The toxicity of phoxim to the 1st instar nymph was 21.17 times compared to that of 5th, it was the highest. The toxicity of triazophos was higher than that in nymph stage, but the toxicity of phoxim was higher in adult stage.2. The effects of 5 factors were studied on the reaction of CarE and the substrate in orthogonal test. The 5 factors were the substrate concentration, the enzyme concentration, the pH of buffer solution, the reaction temperature and the reaction time. The result showed that the best determining condition was that 5 factors were respectively the substrate concentration was 1.2×10^-3 mol/L, the enzyme concentration was 5 heads/mL, the pH of buffer solution was 6.2, the reaction temperature was 40℃and the reaction time was 10 min.3. The protein content of P. sinica showed the evident growth trend as the instars went older. The activities of CarE became higher as the instars went older in nymph stage of P. sinica, but the activity of adult became lower. The 1st instar nymph had the lowest activity; the activities of other instars had a great increase compared with the 1st instar. The activities of CarE were significant differences among the instars (p<0.05).4. Kinetic study of CarE showed that there was existed certain heterogeneity among instars. The Km value and Kcat increased with the instars went older. The low instar nymphs (1 3 instars) were superior to high instars in affinity of CarE toα-NA, that was the low instar nymphs were more sensitive. There was a positive correlation between the catalytic activity and the instars. The catalytic activities of high instar nymphs were higher than that of low instar nymphs, and the adult had the highest catalytic activity.5. The median inhibitory concentration (IC₅₀) of two organophosphorus pesticides to P. sinica increased with the instars went older. The IC₅₀ of triazophos to CarE was larger than that of phoxim in the same instar. The lower susceptibility of P. sinica to the organophosphorus pesticides was relationship with the higher characteristic of CarE.