Abstract: To reveal the approach of entomopathogenic fungus Beauveria using glucide in host insect hemolymph as nutrition, we investigated the changes of trehalase activity and contents of trehalose and glucose in larval hemolymph of Dendrolimus tabulaeformis Tsai et Liu after infection with Beauveria brongniartii (Sacc.) Petch 2382 strain. After the 4th instar larvae of D. tabulaeformis were infected with the strain, the acid trehalase activity in their hemolymph was significantly higher than that in control groups, reached the highest level (0.2786 U/mg) at 3 d after infection, and then dropped slowly during 4-6 d after infection. The trehalose content in larval hemolymph in treatment groups was significantly lower than that in the control, began to decrease at 4 d after infection and reached the lowest level at 6 d after infection, which was consistent with the dynamics of the acid trehalase activity. By contrast, the glucose content was higher in treatment groups than in the control. The glucose content in larval hemolymph in treatment groups increased quickly in 1-3 d with a peak (7.7615 mmol/L) at 3 d after infection, and then decreased gradually. These results suggest that after entering into the hemolymph of D. tabulaeformis, B. brongniartii can produce acid trehalase that hydrolyzes trehalose into glucose for the use by the fungus as nutrition, and a series of physiological metabolism and biochemical reaction result in blood sugar imbalance in host insect.

Key words: Entomopathogenic fungi, Beauveria brongniartii, Dendrolimus tabulaeformis, hemolymph, trehalase, trehalose, glucose