The Study On Virulence And Pathology Of Cydia Pomonella Granulovius-zy On Its Host

Studies on the Cydia pomonella granulovirus Zhang-ye strain(CypoGV-zy) were conducted for susceptibility of the Cydia pomonella larvae at different instar to CypoGV-zy; Pathological process of the Cydia pomonella larvae was infected by CypoGV-zy. The main results were summarized as follows:1. The virulence for Cydia pomonella granulovirus isolated from Zhangye (CypoGV-zy) was carried out by bioassay. The results show that the LD50 were 4.55×103 OBs/ml, 1.20×104 OBs/ml, 3.43×104 OBs/ml and 2.11×105 OBs/ml for first, second, third and fourth instar larvae, respectively. The first to three instar larvae were very sensitive to CypoGV-zy for the corrected mortality were 100% at 7-9 d after infection at a concentration of 0.50×105OBs/ml. The LT50 were all within 5 d for 1-3 instar (0.50×105OBs/ml), which they were 3.59d, 4.07d and 4.66d for firs to third instar, respectively. However, the LT50 for fourth instar was 7.6d longer that others. And the LT90 were 5.51d, 5.91d, 6.53d and 16.06d for first to fourth instars, respectively at the same infection condition. The results indicate that the domestic isolate of CypoGV-zy is a potential biological control agent for C. pomonella in China.2. Pathological variety occurred in cells of different tissue and cell after larvae fed on the CypoGV-zy. By 1d p.i., the virions were found in the fat body tissue. At 2~4d p.i., virions and OBs were obserbed throughout a limited number of midgud cells; The fat body tissue showed a high degree of dissociation; Virions (v) and occlusion bodies (OB) at different stages in the occlusion process were obserbed. At 4~6d p.i., many cells with ruptured plasma membrane were observed; The contents of these cells were liberated into the hemolymph; Infection of the epidermis was also extensive,and became thins. At 6d p.i., the 3rd instar larva began to death, edema and liquefaction. First, the virus infection middgut tissue cells body, followed by adipose tissue cells in the body wall. In addition, the virus replication occurs in the cytoplasm of fat cells cell nuclears were damaged over time gradually. The results of this study for the thorough research to the viruses isolated strains and use of biological control.This study provided important theoretical support, not only the native viruses isolated strains on Cydia pomonella has strong toxic, also from the aspect of pathology organization, cell pathology shows its strong virulence on physiological processes. It is provides important theoretical support for further research on the viruses isolated strains and use of biological control.