Emerging virulence arising from hybridisation facilitated by multiple introductions of the sunflower downy mildew pathogen Plasmopara halstedii

► Plasmopara halstedii is invasive in France, rising from 1 to 14 phenotypes in 40 years. ► Cluster analyses and mtDNA profiles of 147 samples revealed three distinct groups. ► Phenotypes were found to be spatially structured and samples within phenotype were closely related. ► Mixed ancestry observed in recently emerged endemic phenotypes indicates hybridisation.