Selection of a Morphological Variant ofAutographa californicaNuclear Polyhedrosis Virus with Increased Virulence Following Serial Passage inPlutella xylostella

Difficulty in controlling diamondback moth,Plutella xylostella,has promoted interest in using baculoviruses such asAutographa californicamultiembedded nuclear polyhedrosis virus (AcMNPV) as a biocontrol agent. Selection of variants with increased virulence is an attractive option for increasing the...

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Bibliographic Details
Published in:Journal of invertebrate pathology 1997-05, Vol.69 (3), p.205-211
Main Authors: Kolodny-Hirsch, Douglas M., Van Beek, Nikolai A.M.
Format: Article
Language:English
Subjects:
Autographa californicaMNPV
baculoviridae
biological control
genotypic variant
Heliothis virescens
Plutella xylostella
serial passage
Spodoptera exigua
Trichoplusia ni
virulence
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Summary:Difficulty in controlling diamondback moth,Plutella xylostella,has promoted interest in using baculoviruses such asAutographa californicamultiembedded nuclear polyhedrosis virus (AcMNPV) as a biocontrol agent. Selection of variants with increased virulence is an attractive option for increasing the utility of AcMNPV as a viral insecticide. In this study, wild-type AcMNPV was serially passaged 20 times in third-instar diamondback moth and biological and biochemical properties of the passaged and parental isolates were assessed. Compared to wild-type AcMNPV, the virulence of polyhedral occlusion bodies (OBs) from passaged AcMNPV for second-instar diamondback moth was increased approximately 15-fold. In contrast, the bioactivity of the passaged isolate forSpodoptera exigua, Trichoplusia ni,andHeliothis virescensneonate larvae remained unchanged. After 1 passage inS. exigua,OBs of passaged AcMNPV retained their infectivity to diamondback moth. Restriction endonuclease analyses of DNA purified from occlusion bodies of the wild-type and the passaged AcMNPV showed marked differences between passaged and wild-type AcMNPV. Electron micrographs of OB thin sections revealed that OBs of passaged AcMNPV had a greater number of virions and fewer nucleocapsids per virion than OBs of wild-type AcMNPV. Also, singly enveloped nucleocapsids derived from passaged and wild-type AcMNPV were equally potent toward second-instar diamondback moth. These results suggest that increased virulence of serially passaged AcMNPV was based, at least in part, on changes in virus morphology.
ISSN:0022-2011
1096-0805
DOI:10.1006/jipa.1997.4659