Khunna sombat bang prakan lae phonkhong saphap waetlom thimi to prasit thiphap lae khwam khongthon khong chua virus khong non krathuhom, Spodoptera exigua Hubner.
1985
Sirinun Aemprapa
The nuclear polyhedrosis virus of the beet armyworm, Spodoptera exigua Hubner, can be purified by putrefaction, filtration and linear sucrose density gradient centrifugation. The milky-white polyhedral band was observed approximately 4.5 centimeters from the miniscus containing highly purified polyhedra. Transmission and scanning electron microscopic observations of the virus indicated that it was a nuclear polyhedrosis virus of multiple-embedded type. Viral inclusion bodies were polyhedral in shape with the mean diameter of 1.238 micrometers. The shape and size of the virions varied in accordance with the number of the nucleocapsids present in each envelope. Nucleocapsids were rod-shaped with the mean lengths and widths of 51.275 x 324.875 nanometers. Ultraviolet absorption spectrum of purified polyhedra showed a 260/280 ratio of 1.03. The extinction coefficient value of the purified polyhedra was 4.658. Histopathological studies of infected cell showed that infection occurred in the nuclei of fat bodies, hypodermis and tracheal matrix. Results from the studies of the environmental effects on the efficiency and persistence of the NPV of the beet armyworm indicated that sunlight had drastical effect on the virus. Within an equal period of time, the efficiency of the NPV exposed to direct sunlight decreased significantly compared with those in shade. However, the virus maintained in shade outside the building for more than 3 days lost its efficiency by 50 percent. The best storage condition of the virus was in cold place with temperature below 8C. Keeping in soil with the ambient temperature of 20 +- 1C, prolonged the virus efficiency.
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