A Novel Alphabaculovirus from the Soybean Looper, Chrysodeixis includens, that Produces Tetrahedral Occlusion Bodies and Encodes Two Copies of he65.

Robert L Harrison,Holly J R Popham,Daniel L Rowley

doi:10.3390/v11070579

Robert L Harrison, Holly J R Popham + Show 1 more

Open Access

https://doi.org/10.3390/v11070579

Copy DOI

Abstract

Isolates of the alphabaculovirus species, Chrysodeixis includens nucleopolyhedrovirus, have been identified that produce polyhedral occlusion bodies and infect larvae of the soybean looper, Chrysodeixis includens. In this study, we report the discovery and characterization of a novel C. includens-infecting alphabaculovirus, Chrysodeixis includens nucleopolyhedrovirus #1 (ChinNPV#1), that produces tetrahedral occlusion bodies. In bioassays against C. includens larvae, ChinNPV #1 exhibited a degree of pathogenicity that was similar to that of other ChinNPV isolates, but killed larvae more slowly. The host range of ChinNPV#1 was found to be very narrow, with no indication of infection occurring in larvae of Trichoplusia ni and six other noctuid species. The ChinNPV#1 genome sequence was determined to be 130,540 bp, with 126 open reading frames (ORFs) annotated but containing no homologous repeat (hr) regions. Phylogenetic analysis placed ChinNPV#1 in a clade with other Group II alphabaculoviruses from hosts of lepidopteran subfamily Plusiinae, including Chrysodeixis chalcites nucleopolyhedrovirus and Trichoplusia ni single nucleopolyhedrovirus. A unique feature of the ChinNPV#1 genome was the presence of two full-length copies of the he65 ORF. The results indicate that ChinNPV#1 is related to, but distinct from, other ChinNPV isolates.

Highlights

The soybean looper, Chrysodeixis includens (Walker) (Lepidopera: Noctuidae), is a defoliating insect pest found throughout the Americas, from Quebec to southern South America [1]
Electron microscopy revealed that ChinNPV#1 occlusion bodies (OBs) possess a distinctive tetrahedral shape (Figure 1A,B) reminiscent of the OBs produced by Thysanoplusia orichalcea single nucleopolyhedrovirus (ThorSNPV), an alphabaculovirus isolated from Indonesian specimens of Thysanoplusia orichalcea [34]
The ChinNPV#1 OBs ranged in size from 0.82 to 1.62 μm per side, and contained virions consisting of singly-enveloped nucleocapsids measuring 230 × 27 nm (Figure 1C,D)

Summary

Introduction

The soybean looper, Chrysodeixis includens (Walker) (Lepidopera: Noctuidae), is a defoliating insect pest found throughout the Americas, from Quebec to southern South America [1]. Efforts to control soybean looper populations have relied primarily on chemical insecticides, but the occurrence of resistance to many different insecticides has prompted the search for alternative methods of control [4,5,6]. Lepidopteran pests such as C. includens have been controlled with biopesticides based on viruses of the family Baculoviridae [7,8].

Methods

Results

Conclusion