Resynthesizing Brassica napus with race specific resistance genes and race non-specific QTLs to multiple races of Plasmodiophora brassicae

Abstract Clubroot disease in canola (Brassica napus) continues to spread across the Canadian prairies. Growing resistant cultivars is considered the most economical means of controlling the disease. However, sources of resistance to clubroot in B. napus are very limited. In this study, we conducted interspecific crosses using a B. rapa line (T19) carrying race-specific resistance genes and two B. oleracea lines, ECD11 and JL04, carrying race non-specific QTLs. Employing embryo rescue and conventional breeding methods, we successfully resynthesized a total of eight B. napus lines, with four derived from T19 × ECD11 and four from T19 × JL04. Additionally, four semi-resynthesized lines were developed through crosses with a canola line (DH16516). Testing for resistance to eight significant races of Plasmodiophora brassicae was conducted on seven resynthesized lines and four semi-resynthesized lines. All lines exhibited high resistance to the strains. Confirmation of the presence of clubroot resistance genes/QTLs was performed in the resynthesized lines using SNP markers linked to race-specific genes in T19 and race non-specific QTLs in ECD11. The developed B. napus germplasms containing clubroot resistance are highly valuable for the development of canola cultivars resistant to clubroot.