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TECHNICAL SESSION: Indirect Measurement of Disease Development / Spread

Linking sources and sinks in the long distance aerial dissemination of ubiquitous pathogens
Cindy Morris - INRA, Plant Pathology Research Unit. Addur Sigurbjörnsdóttir- University of Akureyri, Odile Berge- INRA, Caroline Guilbaud- INRA, Plant Pathology Research Unit, Paula Darwin- University of Reading, Biological Sciences, Oddur Vilhelmsson- University of Akureyri, Charlotte Chandeysson- INRA, P

The few cases where long distance aerial trajectories of plant pathogens from source to sink have been confirmed have specific traits: i) there are a limited number of sources, ii) sinks emerge along paths of air movement, and iii) sink and source populations have low enough genetic diversity to facilitate statistical comparisons of their population structures. Whereas rust fungi have all these traits, ubiquitous, highly diverse pathogens with broad host ranges do not - and this impedes understanding the dimensions of their natural spread. Our objective is to link sources, sinks and the long distance aerial trajectories of dissemination of ubiquitous pathogens. Here we have focused on Pseudomonas syringae because of its association with atmospheric processes of the water cycle. Its capacity to incite freezing of cloud water droplets and precipitation fosters its fall-out from long distance travel in air masses. For a sink where we collected P. syringae in snowfall - the observatory at Jungfraujoch, CH (46.5475° N, 7.9792° E, 3500 m altitude) - we examined the air mass trajectories of these snowfalls to identify possible sources. From one potential source – ground cover in northern Iceland – we have collected hundreds of strains of P. syringae. We present the comparison of the genetic diversity of Icelandic strains with strains from Jungfraujoch and other sites to assess if atmospheric connectivity between sites assures long distance dissemination of P. syringae.