Affiliation:
1. Departamento de Producción Agraria, Universidad Pública de Navarra, Pamplona, Spain
2. Laboratoire de Pathologie Comparée, UMR 5087, INRA-CNRS-Université de Montpellier II, Saint Christol-lez-Ales, France
Abstract
ABSTRACT
A Nicaraguan field isolate (SfNIC) of
Spodoptera frugiperda
nucleopolyhedrovirus was purified by plaque assay on Sf9 cells. Nine distinct genotypes, A to I, were identified by their restriction endonuclease profiles. Variant SfNIC-B was selected as the standard because its restriction profile corresponded to that of the wild-type isolate. Physical maps were generated for each of the variants. The differences between variants and the SfNIC-B standard were confined to the region between map units 9 and 32.5. This region included PstI-G, PstI-F, PstI-L, PstI-K and EcoRI-L fragments. Eight genotypes presented a deletion in their genome compared with SfNIC-B. Occlusion body-derived virions of SfNIC-C, -D and -G accounted for 41% of plaque-purified clones. These variants were not infectious per os but retained infectivity by injection into
S. frugiperda
larvae. Median 50% lethal concentration values for the other cloned genotypes were significantly higher than that of the wild type. The variants also differed in their speed of kill. Noninfectious variants SfNIC-C and -D lacked the
pif
and
pif-2
genes. Infectivity was restored to these variants by plasmid rescue with a plasmid comprising both
pif
and
pif-2
. Transcription of an SfNIC-G gene was detected by reverse transcription-PCR in insects, but no fatal disease developed. Transcription was not detected in SfNIC-C or -D-inoculated larvae. We conclude that the SfNIC population presents high levels of genetic diversity, localized to a 17-kb region containing
pif
and
pif-2
, and that interactions among complete and deleted genotypic variants will likely influence the capacity of this virus to control insect pests.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology