Impact of synergistic interaction between V. Longisporum and L. maculans on canola yield 

Key Result

This project is still in progress, but aims to explore the compound effect of blackleg and verticillium stripe on susceptible and blackleg-resistant canola. This project will also discover new sources of resistance for verticillium stripe, develop susceptible and resistant control check lines for verticillium pathology tests, and develop and test the durability of B. napus introgression lines with multiple resistance genes against blackleg.

Project Summary

Blackleg and verticillium stripe, caused by the fungal pathogens Leptosphaeria maculans (Lm) and Verticillium longisporum (Vls), respectively, are two important canola diseases in Canada and other canola-growing countries. Blackleg was a severe disease in the 70s and 80s in Canada, that has been effectively controlled by the introduction of resistant cultivars. However, the breakdown of disease resistance genes due to the emergence of new virulent isolates is a cause for concern. Combining several resistant genes (R gene pyramiding) could offer more long-lasting protection against blackleg disease.

In Canada canola yield losses due to blackleg is estimated at 17% on average (1). The impact of Vls on canola production in Canada is not known but an average yield loss of 10-50% has been reported in other countries (2). Blackleg and verticillium stripe are often seen together however the impact of co-infection of Vls and Lm on canola is not known.

To address these questions and provide tools and resources for better management of blackleg and verticillium stripe, we will generate canola lines with multiple resistance genes against blackleg and compare the durability of these lines with single resistance gene lines.

New sources of genetically-resistant canola lines will be identified and used in breeding against verticillium stripe disease. The researchers will also compare the effect of co-infection by Vls and Lm on the growth and seed production of canola susceptible to both pathogens compared to Vls or Lm infection alone.

It is well documented that plants pre-exposed to non-virulent pathogens are immunized against infection by subsequence infection. To find out if this applies to blackleg and verticillium stripe, the researchers will inoculate canola resistant to blackleg but susceptible to Vls, first with Lm and then with Vls. Similarly, canola resistant to verticillium stripe but susceptible to blackleg will be inoculated with Vls and then with Lm. Disease will be evaluated to determine the effect of resistance to Lm on Vls and vice versa. Finally, the blackleg and/or verticillium stripe-resistant lines will be made available to the industry and researchers to be used as standard checks in field trials.