Clubroot, caused by the obligate parasite Plasmodiophora brassicae Woronin, is an important disease of crucifers. In Canada, clubroot has traditionally occurred on cruciferous vegetables in British Columbia and the eastern provinces, where it can result in major losses (Rimmer et al. 2003). Its discovery in 2003 on 12 canola (Brassica napus L.) fields in the Edmonton, Alberta region was a cause for concern, as this was the first report of clubroot on canola in the Canadian prairies (Tewari et al. 2005). Infection by P. brassicae results in the formation of galls on affected roots, which interfere with water and nutrient uptake and can lead to significant yield and quality losses. Moreover, the pathogen produces resting spores that can remain viable in the soil for many years, serving as inoculum for the infection of future crops.