Characerization of the Nuclear Polyhedrosis Virus of the Cotton Bollworm, Heliothis armigera

Abstract

The nuclear polyhedrosis virus (NPV) was is isolated from the cotton bollworm, Heliothis armnigera found in Thailand. Ultrastructural studies revealed the virus of single embedded type with the characteristic symptoms of the NPV infection. The virus inclusion bodies (polyhedra) varied considerably in shape ranging from spherical to cuboidal with the sizes of 0.98 µm. The virions and nucleocapsids were rod-shaped with the mean width and length of 72.79 x 354.79 nm. And 30.13 x 276.87 nm. Respectively. Virus propagation was achieved by os inoculation of the third instar larvae with the preparation of polyhedra. The polyhedra were extracted from infected larvae and purified by low speed centrifugation. Virus particles were released from polyhedra by sodium bicarbonate dissolution. The viral nucleic acid, extracted by phenol: chloroform treatment and precipitated by absolute ethyl alcohol, had a 260/280-nm. Ratio of 2.01. Nucleic acid type was confirmed by DNase and RNase treatments. Digestion of the DNA genome with EcoRI, Hind II, PstI, SacII, HpaI and SacI showed specific restriction endonuclease cleavage patterns. Pre- liminary analysis of restriction endonuclease profiles indicated a molecular weight of approximately 65 x 10⁶ for this viral DNA.