Peronospora farinosa

Peronospora farinosa is a plant pathogen. It causes downy mildew on leaves of wild and cultivated Amaranthaceae: Amaranthus, Atriplex, Bassia, Beta, Chenopodium, Halimione, Salsola, Spinacia, etc. In the past, the forms of Peronospora on these different genera, and their species, were given different species names, but these downy mildews are now generally considered to be forms of one species P. farinosa (see Index Fungorum). Some of the forms on important crop plants have been given names as formae speciales, notably f.sp. betae on sugar beet (= P. schachtii) and f.sp. spinaciae on spinach. Such host specialization possibly also exists with respect to the various wild amaranthaceous hosts of P. farinosa.