Abstract: Previous studies indicated that Bemisia tabaci B biotype, an important invasive pest, had the advantage in interspecific competition with Myzus persicae on tobacco. To explore the effect of physiological adaptability of the two insects on their interspecific competition, the changes of activities of main protective enzymes and digestive enzymes in B. tabaci and M. persicae feeding on tobacco preinfested by B. tabaci were studied using biochemical analysis. The results showed that the activities of PPO and SOD in B. tabaci significantly increased after feeding on the preinfested tobacco plants for 6, 12, 24, 48 and 72 h (P<0.05), and the POD activity in B. tabaci also significantly increased after feeding on the preinfested tobacco plants for 6, 48 and 72 h, respectively (P<0.05). The maximum activities of SOD, PPO and POD in B. tabaci on the preinfested tobacco plants were 1.62, 2.71 and 2.57 times higher than those in the control, respectively. In contrast, the activities of PPO and SOD in M. persicae increased a little in most time-span after feeding on the preinfested tobacco plants, while the SOD activity was obviously suppressed after feeding on the preinfested tobacco plants for 12 h (P<0.05). POD activity in M. persicae was significantly inhibited except after feeding on the preinfested tobacco plants for 24 h (P<0.05). Activities of protease and amylase in B. tabaci significantly increased in all time-span after feeding on the preinfested tobacco plants, and the maximum activities were 1.54 and 1.33 times that in the control, respectively. Activities of protease and amylase in M. persicae did not change after feeding on the preinfested tobacco plants for 6 h (P<0.05); however, the activities were inhibited with the extending of feeding time, and the lowest activities in M. persicae feeding on the preinfested tobacco plants were 0.39 and 0.72 times that in the control, respectively. The results suggest that the increase of the activities of protective and digestive enzymes in B. tabaci feeding on the preinfested tobacco plants should be one of the causes of its higher adaptability compared with M. persicae.

Key words: Bemisia tabaci B-biotype, Myzus persicae, preinfestion, protective enzyme, digestive enzyme, physiological adaptability