Preliminary Study On Susceptible Mechanism Of Bombyx Mori Nuclear Polyhedrosis Virus (BmNPV) To The Silkworm Fed By Cudrania Triloba Leaves

For a long time, silkworm (Bombyx mori L.) became a kind of oligophagous insect. Except mulberry leaves, they also eat Cudrania triloba leaves, leaves of elm tree, leaves of poppy, and so on. Cudrania tricuspidata belongs to Moraceae.There are records showed that people used Cudrania triloba leaves to feed silkworm in ancient times of China and Japan. In modern times, there still have the record that people used Cudrania triloba leaves feeding silkworm larvae. The experiments were mainly about development of the cocoon and it's practical.Present study found that characters and physiological indicators of achievement of silkworm fed on Cudrania triloba leaves were lower than that of mulberry leaves.Viral disease is a most serious kind of disease to the silkworm raising business.It creates about 70% of the total silkworm sickness losses and inhibiting sericultural development well.Among them, the disease caused by BmNPV is common and the loss is biggest. So, inquiring the cause of BmNPV seems to be important to control the disease for the sericulture production. The study showed that the occur of viral disease related to temperature, humidity and nutrition of leaves,but the factors remain unclearly.Therefore, we used silkworm as materials which fed on Cudrania triloba leaves and mulberry leaves in the test to explore the relationship between forage and occurrence of BmNPV and the relationship between occurrence of BmNPV and activities of resistance-related enzymes of the silkworm.Through finding out the reason of susceptibility by constructing a silk-silkworm system with silkworm reared on Cudrania triloba leaves.our purpose is to in-depth study of infection mechanism of anti-BmNPV silkworm The experimental results are as follows: 1 LD50,ID50The results showed that the infective dose 50 (ID50) and lethal dose 50 (LD50) of silkworm feeding on Cudrania triloba leaves were 1.319×105 PID/head and 1.632×105 PID/head respectively, being only about 1/2 and 1/4 to those of the larvae feeding on mulberry leaves.The ID50 and LD50 of silkworm feeding on mulberry leaves were 2.731×105PID/head and 6.286×105 PID/head respectively. Compared by the silkworm fed on mulberry leaves, the resistance to infection and pathogenesis of silkworm fed on Cudrania triloba leaves to infection of BmNPV is poorer.2 Red fluorescent protein (RFP)The synthesis of RFP in the midgut was related with chlorophyll, but was not positively correlated. We suggest that the use of chlorophyll has a certain degree of saturation. At the same time, we found that the amount of digestive juice from silkworm of mulberry leaves was more than that of Cudrania triloba leaves, but the concentrations of RFP in digestive juice from silkworm of mulberry leaves was less than that of Cudrania triloba leaves.In general, the amount of RFP was little different from silkworm mulberry leaves rearing and that of Cudrania triloba leaves.Cudrania triloba leaves had no significant effects on RFP in intestinal.3 Lipase,Trypsin and ChymotrypsinIn both larvae feeding on Cudrania triloba leaves and mulberry leaves, activities of lipase, trypsin and chymotrypsin in the middle of intestinal showed maximum,but the activities in larvaes feeding on Cudrania triloba leaves was significantly lower than that of mulberry. The activities of the 3 enzymes in 5th star silkworm fed on Cudrania triloba leaves were much lower than that of mulberry leaves, while the activities of LiP and TP in 5th silkworm fed on Cudrania triloba leaves were significantly lower. So we suggest that the level of LiP and TP activity response to the resistance levels of the silkworm directly.4 Glutothine-transferase and Mixed-function oxidasesThe activities of Glutothine-transferase and Mixed-function oxidases in 5th silkworm fed on mulberry leaves were much lower than that of Cudrania triloba leaves. This may be due to some toxic ingredients or metabolites in Cudrania triloba leaves induct the activities of Glutathione transferase and Mixed-function oxidases increased in vivo.