| Clubroot disease, caused by Plasmodiophora brassicae, poses a threat to the Canadian canola industry, and breeding of resistant cultivars is urgent. The objective of this study was to identify Brassica germplasm possessing resistance to Canadian P. brassicae pathotypes based on greenhouse screening. Germplasm resistant to local pathotype(s) is the prime requirement for breeding clubroot resistant cultivars. Race-specific to broad-spectrum resistance was identified in the diploid species B. rapa (AA) and B. oleracea (CC), and in the amphidiploid B. napus (AACC). The diploid B. nigra (BB) also showed race-specific to broad-spectrum resistance; however, the two amphidiploids with B. nigra as one of the parental species viz., B. juncea (AABB) and B. carinata (BBCC) were completely susceptible. The occurrence of resistance in the diploid and amphidiploid Brassica species is discussed in the light of their evolution, and a differential set for identification of Canadian clubroot pathotypes is proposed. |
