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Acquisition of Erwinia amylovora by Drosophila melanogaster

Matthew Boucher: Cornell University

<div>Fire blight, <em>Erwinia amylovora</em>, is an economically significant disease of rosaceous plants that causes major loss of apple and pear crops across the globe. Diseased tissues ooze a mixture of plant sap, <em>E. amylovora</em>, and bacterial exopolysaccharide, which collectively serves as the primary source of inoculum for new infections. Insects have long been implicated as passive vectors of <em>E. amylovora</em>, but recent research suggests that insects, notably flies, play a more intimate role in the evolutionary history of this disease. The purpose of this project is to evaluate interactions between flies and ooze to understand whether <em>E. amylovora </em>manipulates insects as alternative hosts or vectors. Here, we begin detailing how flies acquire <em>E. amylovora</em> using <em>Drosophila melanogaster</em> as a model. Flies were fed ooze out of a capillary tube for 3, 6, 12, 24, and 48 hours to evaluate the effect of exposure time on acquisition. Flies were homogenized and plated on Crosse-Goodman media to obtain <em>E. amylovora </em>colony forming units. We tested whether mating status, hunger state, fly sex, and/or amount of ooze consumed affected <em>E. amylovora </em>counts in individual flies. We expect exposure time to positively affect the overall rate of positive samples, while other variables will affect CFU. The effect of bacterial phytopathogen exudates on insect behavior and vectoring capability is relatively understudied, and a better understanding of such interactions may lead to better vector control strategies in agricultural systems.</div>