2011. Breeding for clubroot resistant spring canola (Brassica napus L.) for the Canadian prairies: Can the European winter canola cv. Mendel be used as a source of resistance? Can. J. Plant Sci. 91: 447Á458. Canola (Brassica napus L.) cultivars resistant to clubroot disease, caused by Plasmodiophora brassicae, are desired by the Canadian canola growers. Different genotypes of its two parental species B. rapa and B. olaeacea carry resistance to this disease. Furthermore, the European winter canola cultivar Mendel, which was bred through introgression of resistance from its parental species, also carries resistance to P. brassicae pathotypes prevelent in Europe. The objective of this study was to investigate the usefulness of resistance of Mendel for the development of clubroot-resistant canola cultivars for the Canadian prairies. For this, crosses between Mendel and two Canadian spring canola lines were made and pedigree breeding was followed. Plants with spring growth habit and resistant to P. brassicae pathotype 3 were recovered in the F 2 generation, apparently due to the involvement of major genes in the control of clubroot resistance and vernalization requirement. However, repeated selection over several generations was needed for the improvement of earliness. Most of these resistant lines also showed resistance to P. brassicae pathotypes 5 and 6, and had oil, protein, glucosinolate and saturated fatty acids acceptable to meet the Canadian canola standard. The test hybrids produced using the resistant F 6 lines and a male sterile line of the Male Sterility Lembke (MSL) system showed resistance to all three pathotypes in most cases. Furthermore, conversion of these clubroot resistant lines into cytoplasmic male sterile (CMS) line of the INRA-Ogura system and evaluation of the BC 2 CMS families for resistance revealed the possibilities of using clubroot resistant CMS lines for the development of clubroot resistant F 1 hybrid cultivars. However, despite rigorous selection for resistance performed in different generations, a small number of plants with visible disease symptoms appeared in some of the advanced generation pedigree lines and test hybrids, which is possibly due to the involvement of additional gene(s) in the control of clubroot resistance in these lines. Thus, data presented in this paper demonstrate the possibility of using the clubroot resistance of Mendel for the development of open-pollinated as well as hybrid canola cultivars for the Canadian prairies.