Spreading and global pathogenic diversity of sunflower downy mildew Review

Since almost a century, sunflower cultivation is endangered by Plasmopara halstedii (Farlow) Berlese & de Toni, a biotrophic oomycete causing downy mildew symptoms. The pathogen has conquered four of the five continents, and through high genetic plasticity recurrently avoided being reliably controlled by the introduction of resistant host cultivars in sunflower production. This paper attempts to retrace the historic routes of sunflower downy mildew spreading from its North American origin into Europe, South America, Asia and Africa. An update of the global diversity of pathotypes will be provided and critically discussed. Finally, the limits of the currently applied bioassay-based techniques for diversity assessment are pointed out and an alternative for continuous and area-wide monitoring is discussed.