Peronospora

Peronospora is a genus of downy mildews that are obligate plant pathogens. They can cause severe damage to many different cultivated crops, as well as wild and ornamental plants. Peronospora is most closely related to Pseudoperonospora, and together they form the clade of downy mildews with coloured conidia. Peronospora has far more species than any other genus of the downy mildews. However, many... (Wikipedia)