CpGV-M Replication in Type I Resistant Insects: Helper Virus and Order of Ingestion Are Important.

Aurélie Hinsberger,Miguel Lopez-Ferber,Sean Moore,Caroline Knox,Tamryn Marsberg,Christine Blachère-Lopez

doi:10.3390/v13091695

Abstract

The genetic diversity of baculoviruses provides a sustainable agronomic solution when resistance to biopesticides seems to be on the rise. This genetic diversity promotes insect infection by several genotypes (i.e., multiple infections) that are more likely to kill the host. However, the mechanism and regulation of these virus interactions are still poorly understood. In this article, we focused on baculoviruses infecting the codling moth, Cydia pomonella: two Cydia pomonella granulovirus genotypes, CpGV-M and CpGV-R5, and Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV). The influence of the order of ingestion of the virus genotypes, the existence of an ingestion delay between the genotypes and the specificity of each genotype involved in the success of multiple infection were studied in the case of Cydia pomonella resistance. To obtain a multiple infection in resistant insects, the order of ingestion is a key factor, but the delay for ingestion of the second virus is not. CrpeNPV cannot substitute CpGV-R5 to allow replication of CpGV-M.

Highlights

The use of pathogens is a well-known approach for biological control of insect pests.Among them, members of the baculovirus family are widely used as crop protection products [1,2].The most common way of infection for baculovirus-based biocontrol products is the oral ingestion of the virus by host larvae
Polyhedra are found in the genera Alphabaculovirus, Gammabaculovirus and Deltabaculovirus, previously classified as nucleopolyhedroviruses (NPVs), while granules are found only in the Betabaculovirus that are called granuloviruses (GVs)
In some alphabaculoviruses, called multiple nucleopolyhedroviruses (MNPV), occlusion derived viruses (ODVs) can be polyploid, each ODV containing a variable number of nucleocapsids [5]

Summary

Introduction

The most common way of infection for baculovirus-based biocontrol products is the oral ingestion of the virus by host larvae. Two types of OB can be found in baculovirus, polyhedra and granules. Polyhedra are found in the genera Alphabaculovirus, Gammabaculovirus and Deltabaculovirus, previously classified as nucleopolyhedroviruses (NPVs), while granules are found only in the Betabaculovirus that are called granuloviruses (GVs). When an OB is ingested, the basic pH conditions of the insect midgut induce its solubilisation and liberation of the virions they contain, called occlusion derived viruses (ODVs). In some alphabaculoviruses, called multiple nucleopolyhedroviruses (MNPV), ODVs can be polyploid, each ODV containing a variable number of nucleocapsids [5]. Baculovirus genomes are dsDNA, circular, and around 100 kbp in size. Complete or defective genomes can be present in a nucleocapsid

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