Whitehead, Mark 
ORCID: 0000-0002-0452-1511
(2020)
Genomics for Optimal Aphid Biocontrol.
PhD thesis, University of Liverpool.
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Abstract
Many aphid species cause the reduction of crop yield and monetary loss through feeding and pathogen vectoring. Current pest management strategies for aphids require a range of control methods. However, increased resistance to these methods in certain populations of aphids could impact successful control of these pests. This thesis focuses specifically on the Potato aphid, Macrosiphum euphorbiae, and its innate resistance to the parasitic wasp, Aphidius ervi, a common natural enemy of multiple aphid species. I first discuss population dynamics of M. euphorbiae within the UK and its existence as a handful of strictly asexual genotypes. The distribution is skewed towards genotypes potentially linked to increased host range, while the genotype with low susceptibility to A. ervi (genotype 1) has lower frequency in comparison. A cost associated with A. ervi parasitism-resistance in potato aphids has yet to be demonstrated, while also exhibiting no detrimental effects on fitness in a response to A. ervi challenge as well as potentially having increased tolerance to sub-zero temperatures. To further study innate parasitoid resistance, I generated a draft genome of the genotype 1 Potato aphid (and its obligate symbiont Buchnera aphidicola) using a mixture of long-read sequencing and chromosome scaffolding techniques. Comparative genomics between this aphid genotype with other genotypes of Potato aphid and other aphid species provides a list of immune functioning genes that could play a role in immunity, either through sequence variation or copy number aberrations. However, it is difficult to highlight any specific pathway as the cause of parasitism-resistance to A. ervi. Metabolome comparison between Potato aphid genotypes 1 and 2 highlights variance between genotypes and in response to parasitoid challenge, and suggests the mounting of an immune response through the increased conversion of trehalose to glucose, previously observed in cellular immunity. The data generated over the course of this project will provide useful information for integrated pest management of Potato aphids, as well as providing more resources for further comparative genomics studies within Aphididae.
| Item Type: | Thesis (PhD) |
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| Divisions: | Faculty of Health and Life Sciences > Faculty of Health and Life Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 04 Mar 2020 10:28 |
| Last Modified: | 19 Jan 2023 00:05 |
| DOI: | 10.17638/03073236 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3073236 |
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