Helping western Canadian canola growers win the long-term battle with blackleg is the goal of a new, three-year study.
Funded by the Western Grains Research Foundation, the study is designed to build a new base of knowledge on changing populations of the pathogen that causes blackleg. This will allow producers to better select canola varieties that have resistance to the pathogens of most concern to their growing area. It will also fuel the development of new canola varieties that have better resistance against the ever-shifting pathogen population.
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“There are many commercial varieties available to growers that have some form of resistance to blackleg, but the pathogen population has evolved to the point that there are now at least several strains in isolated areas of Western Canada that show the ability to overcome this resistance,” said Roger Rimmer, who is leading the study.
“We do not know what the basis of resistance is in most cultivars. Thus, these new strains will potentially be damaging on some cultivars but probably not all. To avoid losses, we need the ability to define and monitor the different types of the pathogen that are out there.”
Blackleg, caused by the pathogen L. maculans, is the world’s most important canola disease, Rimmer said. About 100 blackleg-resistant canola cultivars are now registered in Canada, but the genetic basis of the resistance in individual cultivars is unknown. With new types of the pathogen now prevalent in Western Canada and showing virulence on some forms of the resistance, researchers need a better understanding of the pathogen populations and the types of resistance that are available.
“This knowledge will help maintain the economic viability of canola production by providing farmers with better information on which cultivars to select for production in their location,” Rimmer said.
To date, research to define and monitor the types of the blackleg pathogen present in Western Canada was done using a pathogen-based system. The system that was used was based on testing with two cultivars known to have resistance to four pathogen types.
“The challenge with this system is that it only discriminates between four types of the pathogen – PG2, PG3, PG4 and PGT – all of which occur in all or some of the canola growing regions of the Prairies,” Rimmer said.
“However, genetic analysis here and elsewhere has identified nine genes for resistance that occur in Brassica napus. These defined genes can be used to develop a more informative system for describing the pathogenicity of populations of the blackleg pathogen in Western Canada.”
As part of the project, Rimmer and his colleagues plan to develop canola lines that exhibit each of the nine forms of single-gene resistance to blackleg.
“Developing single gene differential lines will provide materials to evaluate more precisely the resistance in new cultivars.”
