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Understanding Phytophthora infestans populations at local and global scales

David Cooke: James Hutton Institute

<div>Late blight, caused by <em>Phytophthora infestans</em>, continues to threaten potato and tomato crops on a global scale. The timing and effectiveness of blight management depends on the pathogen’s response to the environment, primary inoculum type, virulence to host resistance and sensitivity to fungicide active ingredients. The evolving <em>P. infestans</em> population requires management approaches that are tailored to the local population. The need to track the pathogen prompted the Euroblight consortium to collect data on the diversity of <em>P. infestans</em>, analysed with simple sequence repeat (SSR) genetic markers. Surveys of late blight infected crops by collaborators from 2013-2016 has resulted in over 5200 geo-tagged samples from 34 European countries. Standardised protocols and a single data format has allowed a flexible and powerful isolate database, associated analysis tools and a mapping interface to be built. A complex population structure is observed with 70 to 80% of the population dominated by a few widely disseminated clonal lineages; see maps at <a href=""></a>;. The SSR diversity within lineages such as EU_13_A2 has been tracked over time and highlights the local spread of some sub-clonal variants. In contrast to the clones, 20-30% of the sampled European population comprises genetically diverse pathogen populations consistent with local, ephemeral oospore-derived sexual populations. Analysis via an interface with <em>poppr</em>, an R-based population genetics application appropriate for such mixed ploidy and mating system data, is allowing insights into the diversity of the potato late blight pathogen in Europe. Euroblight partners collaborate widely with other regional blight networks that have adopted our approach.</div>

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