Fruit host selection by the olfactory system in the agricultural pest Drosophila suzukii

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This project investigates how the olfactory system of the emerging agricultural pest Drosophila suzukii encodes host odours, and aims to identify attractive ligands and their mixtures that can be used as baits in traps. Endemic to eastern Asia, D. suzukii was first recorded in Spain in 2008 and has since invaded northwards in Europe, reaching the UK in September 2012. D. suzukii is an extreme generalist feeder: the fly lays its eggs in fruit from diverse plant families including strawberry, grape and blueberry. How a generalist insect selects its hosts is a central question in insect-plant relationships. By electrophysiology at the resolution of single sensory neurons, we will test hypotheses of how the olfactory system encodes odours from fruit hosts. Are there shared key ligands in the bouquets emitted by the different hosts, which thereby activate common subpopulations of sensory neurons in the olfactory system that mediate behavioural attraction, or do different host bouquets activate mutually exclusive groups of sensory neurons? Our knowledge of the olfactory system of the model organism Drosophila melanogaster will inform our research on D. suzukii. Assays measuring behavioural attraction to pure single odorants and to multicomponent blends will provide quantitative readouts of processing of olfactory information, and a mathematical model which relates output to input will give insight into the importance of blend recognition. Blends that are attractive in the laboratory are valuable candidate baits for traps to monitor and control D. suzukii populations in orchards. This interdisciplinary project will provide training in aspects of insect behaviour, analytical chemistry and antennal electrophysiology. In the rotation at Rothamsted, the student will acquire skills in behavioural experiments with insects using a Pettersson four-arm olfactometer, focussing on the development of quantification of attractive response to odour dose, and will be trained in biological chemistry methods, including volatile capture from plants and fruits in the field and analysis using high resolution gas chromatography (GC) / coupled GC-MS. The student will participate in lab meetings focussed on Chemical Ecology, which is an area of particular expertise in Rothamsted. The subsequent rotation in Cardiff will introduce the student to the physiology of Drosophila, and the student will learn techniques for extracellular recordings from insect sensory neurons. In Cardiff, the student will interact with a research environment formed by four Drosophila groups, which co-operate closely. Supervisors: Dr Wynand Van der Goes van Naters, Dr Mike Birkett (Harpenden, Rothamsted Research)