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Species specific resistance in aphids to infection by Verticillium lecanii

Species specific resistance in aphids to infection by Verticillium lecanii
Species specific resistance in aphids to infection by Verticillium lecanii

Species of aphid vary in their susceptibility to the entomopathogenic fungus Verticillium lecanii (Zimm) Viégas, attributed to differences in host behaviour, mobility and feeding site (Hall, 1975; Hall and Burges, 1979). However, the degree of susceptibility to infection by the fungus may also be determined in part by host anatomy and physiology. The aim of this investigation was to identify possible mechanisms of species-mediated resistance expressed in the initial stages of fungus infection using six species of aphid.

Significant differences in the number and density of conidia of V. lecanii adhering to aphid cuticle were observed, according to host species, using fluorescence microscopy and image analysis. These were related possibly to the arrangement and amount of epicuticular lipids, which varied widely between the six aphid species studied here. Species of aphid receiving the lowest densities of conidia during spraying had the highest levels of prominent epicuticular lipid and vice versa. There were indications that lower percentage germination of V. lecanii conidia occurred on species with higher levels of prominent epicuticular lipid, although preliminary experiments to measure the effects of epicuticular lipid extracts on the germination of conidia in vitro were inconclusive.

Significantly more conidia (p<0.005) adhered to the siphunculi of the aphids than to any other part of the body, which may make them important areas for infection by V. lecanii. During bioassay work, it was noted that the siphunculi, together with the antennae and leg joints, often had mycelia growing over them before the aphids had died.

The combination of fluorescence microscopy, image analysis and SEM may reveal a link between the dose of conidia received by the aphid and the physical characteristics of the cuticle.

University of Southampton
Girard, Karen
Girard, Karen

Girard, Karen (1996) Species specific resistance in aphids to infection by Verticillium lecanii. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Species of aphid vary in their susceptibility to the entomopathogenic fungus Verticillium lecanii (Zimm) Viégas, attributed to differences in host behaviour, mobility and feeding site (Hall, 1975; Hall and Burges, 1979). However, the degree of susceptibility to infection by the fungus may also be determined in part by host anatomy and physiology. The aim of this investigation was to identify possible mechanisms of species-mediated resistance expressed in the initial stages of fungus infection using six species of aphid.

Significant differences in the number and density of conidia of V. lecanii adhering to aphid cuticle were observed, according to host species, using fluorescence microscopy and image analysis. These were related possibly to the arrangement and amount of epicuticular lipids, which varied widely between the six aphid species studied here. Species of aphid receiving the lowest densities of conidia during spraying had the highest levels of prominent epicuticular lipid and vice versa. There were indications that lower percentage germination of V. lecanii conidia occurred on species with higher levels of prominent epicuticular lipid, although preliminary experiments to measure the effects of epicuticular lipid extracts on the germination of conidia in vitro were inconclusive.

Significantly more conidia (p<0.005) adhered to the siphunculi of the aphids than to any other part of the body, which may make them important areas for infection by V. lecanii. During bioassay work, it was noted that the siphunculi, together with the antennae and leg joints, often had mycelia growing over them before the aphids had died.

The combination of fluorescence microscopy, image analysis and SEM may reveal a link between the dose of conidia received by the aphid and the physical characteristics of the cuticle.

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Published date: 1996

Identifiers

Local EPrints ID: 459807
URI: http://eprints.soton.ac.uk/id/eprint/459807
PURE UUID: b5fcb956-fb4c-435f-b2c3-5bcea3a245ca

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Date deposited: 04 Jul 2022 17:19
Last modified: 04 Jul 2022 17:19

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Contributors

Author: Karen Girard

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