Europe as a bridgehead in the worldwide invasion history of the grapevine downy mildew Plasmopara viticola. Plasmopara viticola strain:Vitis species

Invasive pathogens cause devastating emerging diseases on crops worldwide. The invasiveoomycete Plasmopara viticola is responsible for grapevine downy mildew, a highly destructivedisease of cultivated grapevine ( Vitis vinifera ). The pathogen was introduced into Europe in the1870s with wild American Vitis species and is now present in all grape-growing regionsworldwide. Despite its economic impact, the grapevine downy mildew invasion history is stillpoorly understood. Here, we analysed ~2,000 samples from the most important wine-producingcountries worldwide using gene sequences and microsatellite markers. We found that allpopulations worldwide on the cultivated grapevine V. vinifera derived from a single of the fivecryptic species present in North America, P. viticola f. sp. aestivalis, parasitizing the wildsummer grape V. aestivalis . Compared to native populations, invasive populations displayed adrastic reduction of genetic diversity, with Europe showing the mildest bottleneck.