Occurrence of a granulosis virus from two populations of Plutella xylostella (L.) in India

Populations of the diamondback moth Plutella xylostella (L.) larvae from two locations : Ooty and Oddanchatram (Tamil Nadu State) were found to be infected by a granulosis virus (GV). The virus was highly pathogenic to P. xylostella larvae and was responsible for the collapse of laboratory colonies of the insect. Restriction endonuclease analysis of the viral DNA with Pst 1, Hind 3, Bam H1 and EcoR 1 showed similar profiles indicating that both the isolates of the GV are identical. Pst 1 produced the maximum number of 16 bands, Hind 3 showed 13 and Bam H1 and EcoR 1, both recorded 10 bands. The molecular weight of the viral DNA was found to be 64.05 ± 2.07 X 106 daltons. Results of bioassays showed that the GV was highly pathogenic to P. xylostella larvae with an LC50 of 5.89 occlusion bodies/ mm2 of leaf surface for the second instar larvae. The LT50 was 5.67 days for the highest dose of 2.8 X 104 OB/mm2 and it increased with decreasing concentration of the virus.