Reducing insect pests on cereal crops by exploiting beneficial species interactions

The changing climate is expanding insect pest range distributions and shifting insect phenology leading to desynchronization with natural enemy populations and resulting in increased chances of pest outbreaks. With increasing levels of insecticide resistance, we need to find alternative solutions for pest control in our cropping systems. Promising strategies include manipulating soil microbiomes for increased plant resistance to pests and promoting recruitment of natural enemies for pest control services in crop fields. The soil bacterium Acidovorax radicis N35 can promote the growth of barley plants while simultaneously reducing the growth rates of cereal aphid pests. The effect on sap-sucking aphids is indirect, occurring via plant physiological changes, yet we do not know how this might alter interactions with aphid natural enemies, such as parasitic wasps. Preliminary data from an outside pot experiment suggests that inoculation of plants with this bacterium increases parasitism rates on some barley cultivars while decreasing rates on others. Potentially this is driven by differential changes in plant volatiles that are used by parasitic wasps to locate infested plants, or through changes in the plant resulting in the aphids being better or worse hosts for the wasps.
In this project, we will combine the expertise of the Liverpool PI (Early Career Researcher) on the molecular basis of plant-insect-microbe interactions with Newcastle Co-I (Established Researcher) on the biochemical bases of plant-pest interactions. We will use controlled greenhouse experiments (Liverpool) to determine the role of microbe-mediated plant changes in altering aphid-parasitic wasp interactions across different barley cultivars that vary in the response to aphids and the bacterium. Plant volatiles will be examined (Liverpool) as these are used by the wasps to locate aphid hosts and their expression can be altered by root bacteria. We will then use functional genomics to examine the transcriptome of the aphid pest (Newcastle) to identify genes that are differential expressed across treatments with consequences for the aphid-wasp interaction.

Objective
To determine how beneficial soil bacteria alter barley plant and sap-sucking insect pest chemistry, and the consequences for the natural enemies of insect pests.
Novelty
The drive to find new solutions for sustainable agriculture kick-started a burst of research on the benefits of manipulating the plant microbiome. Here we expand on this to determine wider effects on the interacting community of natural enemies that can exert top-down control on pest populations to complement bottom-up control by the microbes. This will create a step-change towards a more holistic approach to pest control in agroecosystems.
Timeliness
The impact of climate change on the dynamics of pests and soil health are a key priorities identified by the Intergovernmental Panel on Climate Change (IPCC; August 2019), BBSRC, UKRI, the Soil Association, and Horizon 2020. We must produce research outputs that identify key important processes allowing development of practical solutions for future farming. This PhD project also fits within the scope of a BBSRC David Phillips Fellowship at Liverpool (2019-2024), and will benefit from the knowledge of the barley-aphid-microbe system that is central to both projects.