Development of Clubroot Resistant Spring Canola Germplasm and Mapping the Resistance Genes.

Clubroot disease caused by the soil-borne pathogen Plasmiodiophora brassicae Woronin is a major threat to the production of Brassica crops worldwide. Breeding for resistance requires the identification of resistance sources and successful introgression of the resistance gene(s) into crop germplasm. The European winter canola cv. Mendel show resistance to many P. brassicae isolates including pathotypes 3, 5, 6 and 8 that are prevalent in Canada. To introgress clubroot resistance into Canadian spring B. napus canola, crosses between Canadian spring and European winter canola cv. Mendel were done and several resistant lines were developed through pedigree breeding. Two of the resistant lines were further crossed with the clubroot susceptible spring canola line A07-26NR and doubled haploid (DH) populations were produced from the F₁’s. Simple sequence repeat (SSR) markers were used to study the resistance in two DH populations as well as in segregating F₃ and F₄ families derived from the original Canadian spring canola × Mendel cross. The inheritance and molecular mapping studies suggested that a single dominant gene is involved in the control of resistance. The resistance gene was mapped to the A3 chromosome and SSR markers linked to the resistance were identified for use in marker assisted breeding.