Arable - Understanding phenotypic and genetic variation in wing polyphenism in an aphid virus vector

Aphids are among the world's most economically important group of insect pests, causing billions of US dollars of yield loss per annum to a wide range of food and commodity crops. Aphids are, in part, so damaging because they are highly efficient vectors of numerous plant viruses. A remarkable trait exhibited by aphids, that has a major impact on their ability to transmit viruses in crops, is their ability to produce completely different winged and non-winged forms in response to environmental cues. This developmental plasticity is termed wing polyphenism and allows aphids to produce offspring that are optimised for maximum reproductive output (non-winged form) or capable of dispersing via flight (winged forms) in response to environmental conditions.

We recently uncovered marked variation in the extent to which genetically distinct clones of the damaging aphid pest, Myzus persicae, produce winged forms under both crowded (which typically induces wing production) and non-crowded conditions (which typically results in the production of non-winged forms). This finding is important for two reasons. Firstly, the extent to which an aphid genotype produces winged forms will directly impact its capacity to disperse plant viruses through and between crops. Secondly, the identification of variation in aphid wing production in different aphid clones provides an opportunity to identify the genes and genetic variation underpinning this variation.
Despite the importance of this preliminary data, the extent of phenotypic variation in wing polyphenism across diverse populations of M. persicae, and its underpinning genetic basis, remains unknown. The aim of this project is to address this knowledge gap by exploiting a unique biological and genomic resource recently developed for this aphid pest comprising a living library of 110 fully sequenced genetically distinct clones of M. persicae.

In the first objective of the project, we will phenotype each individual M. persicae clone in the living library for wing polyphenism under crowded and uncrowded conditions. The data obtained will provide unprecedented insight into the extent of phenotypic variation in wing polyphenism in M. persicae collected from every continent where crops are grown. Understanding the extent of variation in this key trait will allow us, in future, to much more accurately predict virus transmission in crops. Furthermore, generating robust phenotypic information on wing polyphenism for each clone will allow us to investigate its underpinning genetic basis in Objective 2. For this we will leverage our existing sequence data for each M. persicae genotype in the clone library to identify genes and genetic variation associated with phenotypic variation in wing polyphenism in a way that has never been previously possible. The data obtained will provide fundamental insight into the molecular basis of this adaptive trait, and is a first step in the development of novel interventions that target key genes, or their products, involved in wing production in order to reduce virus transmission.

Aphids are among the world's most economically important agricultural pests. Their pest status is enhanced by their exceptional ability to transmit plant viruses, with aphids transmitting 50% of all insect vectored viruses. A key trait exhibited by aphids that impacts their ability to disseminate viruses in crops is wing polyphenism where a female aphid can asexually produce winged or wingless (flightless) forms dependent on environmental conditions. We have recently shown that genetically distinct clones of the aphid pest, Myzus persicae, can exhibit profound variation in the proportion of winged offspring produced under crowded (which typically induces wing production) and non-crowded conditions (which typically results in the production of non-winged forms). However, the extent of this variation in M. persicae populations and its genetic basis remains unknown. In this project we will exploit a living library of 110 fully sequenced globally sampled clonal lines of M. persicae to: a) understand how wing polyphenism varies across clones collected from every continent where crops are grown, and, b) identify genes and genetic variation associated with this phenotypic variation. The data generated will fundamentally advance our understanding of a key adaptive trait in aphids, and is a prerequisite for the development of accurate predictive models of aphid virus transmission in crops and interventions that target key genes involved in wing production in order to disrupt virus transmission.