Pythium-Polymastum Pathogenic On Oilseed Rape And Other Crucifers

Pythium polymastum has been found in the roots of oilseed rape (Brassica campestris and B. napus), Capsella bursa-pastoris, and Lunaria annua, grown in field soil from widely separated localities in Saskatchewan. It is virulent on rape and 18 other crucifers, and avirulent or only slightly virulent on numerous cultivated plants belonging to other families. This is the first report of the fungus as a pathogen on crucifers. It is suggested that it may play a part in a root-rot complex, that it is indigenous, and that cruciferous weeds act as alternative hosts.