Genetic and biological variation among nucleopolyhedrovirus isolates from the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

A PCR-based method was used to identify and distinguish among 40 uncharacterized nucleopolyhedrovirus (NPV) isolates from larvae of the moth Spodoptera frugiperda that were part of an insect virus collection. Phylogenetic analysis was carried out with sequences amplified from two strongly conserved loci (polh and lef-8) from the 40 isolates in the collection and from eight previously studied S. frugiperda NPV (SfMNPV) isolates. To further distinguish these isolates, analysis was also carried out with sequences from two less-conserved loci, hr4 and hr5. Phylogenetic inference from the sequence data could distinguish among several of the individual isolates and between different groups of isolates from Georgia (USA) and Colombia, South America. A stronger degree of bootstrap support for the phylogenetic trees was obtained with the hr4 and hr5 homologous repeat sequences. Sequencing and phylogenetic analysis detected a relatively high degree of larva-to-larva sequence divergence occurring among isolates of SfMNPV collected from the same field in Missouri, USA. Restriction endonuclease analysis of viral DNA from larvae infected with five isolates from Georgia, Missouri, Louisiana, Florida (USA), and Colombia allowed for further comparison with other previously reported isolates of SfMNPV. Bioassays with these five geographically distinct isolates detected minor differences in virulence. This study highlights the use of PCR to rapidly distinguish and characterize large numbers of historical baculovirus isolates from the same host using minimal quantities of material, and the use of sequences from homologous repeat regions to distinguish closely related isolates of the same NPV species.

Genetic variation and virulence of nucleopolyhedroviruses isolated worldwide from the heliothine pests Helicoverpa armigera, Helicoverpa zea, and Heliothis virescens

“…Template preparation from polyhedra, PCR amplification, and sequencing were carried out as previously described (Rowley et al, 2010). Briefly, polyhedra from the samples were diluted to a concentration of 10 6 polyhedra/ll and solubilized with 1/10 volume 1 M Na 2 CO 3 (pH 11.4) at room temperature for 30 min.…”

High levels of genetic variation within core Helicoverpa armigera nucleopolyhedrovirus genes

“…A major limitation of the cloning and sequencing approach is that the detection of the SNPs is limited to those present within the sequenced clones. Rowley et al [26] used the method, direct sequencing of amplicons after PCR using degenerate primers for highly conserved genes and subsequent phylogenetic inference, developed by Lange et al [27] to distinguish between closely related NPV isolates collected from the same host species in different geographical and temporal regions. Direct sequencing, using traditional capillary-based sequencing, of PCR amplicons has several limitations that reduce its application during viral typing, including the fact that only the most dominant polymorphism will be detected if there are any genetic polymorphisms present within the amplicons.…”

Isolation and identification of a new Bombyx mori nucleopolyhedrovirus strain isolated from Yunnan, China

“…The BmNPV polyhedrin gene is non-essential late gene for BmNPV replication and the ORF contains 738 nucleotides 6 . The polh gene has not only been used in phylogenetic studies but also in the molecular identification of baculoviruses specific to lepidoptera [7][8][9][10] . Baculovirus-repeated ORFs (bro) are widespread among invertebrate viruses.…”