Introgression of clubroot resistance from <i>Brassica oleracea</i> into <i>B. napus</i> by interspecific cross

Cultivation of resistant cultivars is an efficient way of managing clubroot disease in Brassica napus (AACC, 2 n = 38) canola. All available clubroot-resistant cultivars carry resistance in the A genome and some of the resistance genes have become ineffective when used singly after a few years due to the evolution of new Plasmodiophora brassicae pathotypes. This highlighted the need for introducing quantitative resistance from Brassica oleracea (CC, 2 n = 18) into canola . In this study, interspecific crosses between clubroot-susceptible B. napus canola and clubroot-resistant B. oleracea were carried out to develop a canola quality B. napus genotype carrying resistance in the C genome. Selection of progeny from this cross resulted in a gradual increase in resistance over several generations suggesting that multiple loci are involved in its control. Several B. napus genotypes with nuclear DNA content similar to the B. napus parent and showing resistance to P. brassicae were obtained from this cross. A relatively simpler genetic control of the canola quality traits enabled the identification of low erucic acid and low glucosinolate plants among the progeny from this interspecific cross. Thus, the results from this study demonstrated the feasibility of developing clubroot-resistant, spring growth habit B. napus genotype carrying resistance in the C genome. The knowledge and the plant materials from this research will be useful for the development of clubroot resistant canola cultivars and to understand the C genome resistance of B. oleracea in the AC genome background of B. napus.