Studies On Some Biological Characteristics Of Syngrapha Falcifera Multiple Nuclear Polyhedrosis Virus (SfaMNPV) Clone

The studies on the replication of Syngrapha falc~fera Multiple Nuclear Polyhedrosis Virus Clone in sensitive insect cell line-BT 1 -TN5B-4(5Bl), toxicity and restriction endonuclease analysis were reported in this thesis. This Virus was cloned from SfaNPV by plaque purification. The virus was very sensitive to 5B1 cell line. The highest ECV titers in 5B1-sfaMNPV was3.87 X 108/ml TCID50, The maximum PIB concentration was achieved over a period of 144hr (4.0x10~ PIBs/ml.) Under electron microscopy, virus stroma-~ virions and PIB were all observed. It revealed the clone was Multiple Nuclear Polyhedrosis Virus. SfaMNPV-Clone was used test its toxicity to the early third instar larvae of Helicoverpa armigera with that of SfaMNPV-Clone, the LC50 values were 7.14 X 1 O5PIBs/ml and 4.81 X 1 O6PIBs/ml respectively. The third instar larvae of Helicover pa arm igera were infected with SfaMNPV-Clone at the concentration of 1.0 x 1 ~ PIBs/ml and 1 .Ox 106 PIBs/ml, the LT50 was 4.6 days and 4.9days respectively. While when the third instar larvae of Helicover pa arm igera were infected with SfaNPV at the concentration of 1 .Ox 106 PIBs/ml and 1 .Ox 1 ~ PIBs/ml, the LT50 was 5.5 days and 5.0 days respectively. The result showed that the toxicity of SfaMNP V-Clone to Helicover pa armigera larvae was higher slightly than that of SfaNPV. The results also showed the sensitivity is increased as virus concentration increased when larvae instar and temperature were fixed. The genome of SfaNPV was digested by two restriction endonuclease EcoRI and Hind Ill~ producing 18 and 1 7fragments respectively. The sizes were estimated with respect to the mobilities of standard A DNAIEcoRJ+Hindlll fragments .The total genome size of SfaNPV was about I 15.O8Kbp. While digested with restriction endonuclease EcoRl and Hind III the genomic DNA of SfaMNP V-clone produced 19 and 20 fragments, The size of genomic DNA was about 113.88 Kbp. The restriction endonuclease pattern of SfaNPV and sfaMN7PV-clone showed that their genomic DNA were similar, only a few fragments were different.