Introgression of Resistance to Multiple Pathotypes of Plasmodiophora brassicae from Turnip (Brassica rapa ssp. rapifera) into Spring B. napus Canola

Clubroot disease resistance has been introgressed from Brassica rapa into canola following different approaches including a B. napus x B. rapa interspecific cross; however, the details of this cross are not available. To extend our knowledge of this cross for the introgression of resistance to multiple pathotypes, we crossed a clubroot-resistant turnip with a susceptible canola and backcrossed the F-1's to canola. The backcross population was subjected to pedigree breeding with selection for clubroot resistance and canola-quality traits; selection for resistance to pathotype 3H and 3A was performed in the early and advanced generations, respectively. The advanced generation lines were also evaluated for resistance to 3H, 3A, 2B, and 5x, and for field resistance to clubroot, and agronomic and seed quality traits. Following this, we developed canola lines carrying resistance to multiple pathotypes and nuclear DNA content similar to B. napus. Resistance to 3H showed a weak correlation with other pathotypes whereas resistance to 3A showed a strong positive correlation with 5x indicating that resistance to these pathotypes was under a similar genetic control. Thus, the results demonstrate that resistance to multiple pathotypes can be introgressed from a turnip into a canola even when selection for resistance to single pathotype is performed in early generations.