The genetic diversity of natural populations of Myzus persicae, a polyphagous aphid species

Wouters, Roland (2021) The genetic diversity of natural populations of Myzus persicae, a polyphagous aphid species. Doctoral thesis, University of East Anglia.

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The green peach aphid Myzus persicae has a broad plant host range of over 400 plant species from over 40 families and is a significant insect pest of many crops. Furthermore, M. persicae transmits approximately 100 plant viruses and has developed resistance to more than 70 insecticides. So far, knowledge of crop resistance mechanisms to aphids is limited. Sugar beet productions are particularly challenged by insect-vectored viruses and specifically those transmitted by M. persicae. The objectives of the research described in this thesis were (i) to identify resistance to M. persicae within existing sugar beet germplasm and (ii) to investigate the genetic diversity of M. persicae found on sugar beet in field plots around Europe. It was found there is variation in resistance to M. persicae among sugar beet lines and varieties. Moreover, M. persicae clones vary in their ability to colonise sugar beet in laboratory conditions. M. persicae genotype 4106a does have a lower fecundity and survival rate on sugar beet in comparison to the three other tested M. persicae genotypes (US1L, UK_SB and O). Existing microsatellite markers were not specific enough for aphid genotyping. I added to the current population genetics studies of M. persicae by a whole-genome sequencing approach of 99 M. persicae samples collected world-wide. I contributed to obtaining a chromosome-level M. persicae genome assembly of M. persicae genotype O, which was used as the reference genome in a genomics population approach to study the genetic diversity of 99 M. persicae genotypes. Between 8 to 10 populations were predicted within the sampleset of which 5 of the populations were further analysed. There was a considerable degree of differentiation among populations found with FST values ranging from 0.218 and 0.436. Population genetics analyses methods identified 11 selective sweeps, among the 5 populations. These 11 selective sweep areas were further investigated for the underlying genes involved. Multiple genes were found within the selective sweep areas. One of the sweeps associated with M. persicae plant host preference to nicotianae included candidate effector genes. In conclusion, research conducted in this PhD project showed that there is a level of resistance in sugar beet germplasm to some M. persicae clones and that field populations of M. persicae that colonise sugar beet in fields across Europe are highly diverse. These findings represent a significant step towards the identification of new approaches to obtain stable sugar beet resistance.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 18 Oct 2021 14:14
Last Modified: 18 Oct 2021 14:14

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