Enhancement of Mythimna separata Nucleopolyhedrovirus Infection with Viral Enhancing Factor from Spodoptera litura Granulovirus

M. CHAKRABORTY, K. NARAYANAN* AND M. K. SIVAPRAKASH

Department of Agriculture Microbiology, G.K.V.K., University of Agricultural Sciences, Bangalore 560065

Biopestic. Int. 1 (1,2): 109-113 (2005)

ABSTRACT

When the third instar larvae of Mythimna separata (Walker) were exposed to eight doses (2.6x101 to 2.6x108 POB’s/ml) of polyhedral occlusion bodies (POB’s) of nucleopolyhedrovirus of M. separata (MsNPV); the per cent mortality and survival time was found to range from 16 to 100 per cent and 14 to 9 days respectively, depending on the dose of POBs used. Viral enhancing protein fraction purified from Spodoptera litura (Fabricius) granulovirus used at 0.01ml (0.3 mg/ ml) significantly enhanced the mortality of M. separata exposed to varying concentrations of POB’s of MsNPV ranging from 2.6x102 to 2.6x106 POB’s/ml. The percent mortality ranged from 66 to 93 per cent and survival times were from 8 to 5 days. The enhancement index (log10) of the virus was found to be 3.33, i.e reduction of LC50 by nearly 2000 times. The mechanisms involved in viral enhancing protein factor (VEF) from S. litura granulovirus to enhance the infectivity of MsNPV have been discussed.

KEY WORDS : Nucleopolyhedrovirus, viral enhancing factor (VEF), S. litura GV, M. separata NPV.