Abstract: It had been reported that silkworms Bombyx mori reared on cudrang (Cudrania tricuspidata) leaves are sensitive to B. mori nucleopolyhedrovirus (BmNPV). In order to explore the mechanisms of this phenomenon, we investigated the activities of different anti-BmNPV proteins in digestive juice of the silkworm reared on cudrang leaves and mulberry (Morus alba) leaves, respectively. The results showed that there was no significant change in intensity of red fluorescent protein (RFP) in the digestive juice of the silkworm reared on cudrang leaves. However, the enzymatic activities of lipase and trypsin in the silkworm reared on cudrang leaves were 1 421.71±202.60 U/L and 19.67±8.17 U/mL, respectively, much lower than those of the silkworms reared on mulberry leaves, which were 1 976.03±139.92 U/L and 199.18±181.71 U/mL, respectively (P<0.05). The results suggest that the susceptibility of silkworms to BmNPV may be related with the lower activities of lipase and trypsin in digestive juice.

Key words: Bombyx mori, Cudrania tricuspidata, BmNPV, RFP, lipase, trypsin