Identification of clubroot of crucifers on canola (Brassica napus) in Alberta

Clubroot, caused by Plasmodiophora brassicae, was detected for the first time on canola in Alberta. Galling, typical of the disease, was observed on the roots of canola (Brassica napus) plants in a dozen fields near St. Albert, Alberta. The presence of resting spores of the pathogen was confirmed by light and electron microscopy. Pathogen spores were isolated from diseased tissue and used to inoculate roots of B. napus 'Westar', on which they produced symptoms similar to those observed in the field. Resting spores were recovered from galls on inoculated plants. The identification of clubroot on the Alberta canola crop is a matter of concern, as the disease is associated with appreciable yield losses and can only be managed with extended intervals between host crops because other management strategies may be too expensive to implement or are of limited effectiveness. Further studies are underway to determine the extent of the problem.