The molecular characterisation of a baculovirus isolated from trichoplusia ni

Abstract

In South Africa there are more than 106 insects pests which attack a wide variety of crops. The top ten or twenty of these can seriously limit successful production on the farm. Costs involved in controlling these pests are considerable, often higher than the value of the crop itself. Trichoplusia ri (common name: cabbage looper) is a pest that can cause considerable damage to a wide variety of economically important crops. Although Trichoplusia ni has successfully been controlled with synthetic chemical pesticides, awareness about the negative impact of these control measures on the environment has necessitated the development of safer alternatives. Additionally, cabbage looper resistance to the commonly used pesticides has been reported. Since a Trichoplusia ni multiple nuclear polyhedrosis virus has previously been used in the effective control of the pest, the potential of characterizing a South African baculovirus isolate showed great potential. A latent baculovirus infecting a field population of Trichoplusia ni was isolated and characterised. Initial DNA and protein characterization identified it as a novel baculovirus. The aim of this research was to characterise the baculovirus at a molecular level. This could lead to future improvement of the viral insecticidal properties The family Baculoviridae include more than 600 viruses with only nineteen receiving species status (Murphy et ol., 1995). The genome sequencing and mapping of NPVs could prove important in determining the relationships between these viruses. Additionally, it could be useful in understanding the importance of gene arrangement and the essential domains of genes' This could provide insight into the crs- and trans-regulation among genes (Jin et al., 1997). The determination of gene order and arrangement of the novel baculovirus isolated from a field population of Trichoplusia ni was presented in Chapter 2. Data were used to construct a partial functional map of the TniSNPV genome. Subsequently, the order and homology of genes identified were used as a phylogenetic marker, identi$,ing TniSNpv as a putative member of the Group II NpVs.