For years, scientists have bred clubroot resistant canola varieties to combat issues with the disease, but researchers have found some new virulent clubroot pathotypes that can overcome resistance.
Steven Strelkov, a Professor of Plant Pathology at the University of Alberta, says they have found 11 distinct strains of clubroot that have broken resistance.
Strelkov says since 2013, they've found 24 fields with such issues.
"They have slightly different characteristics. That seems to suggest that it wasn't just that the resistance broke down in a single field and the strains spread from there.
Likely, different strains were independently selected for individual fields, distinct from each other," he said.
Strelkov also explains crop rotation can help in combating this issue.
"In most cases where we found resistance had been defeated, the resistance canola was being grown in a short rotation - often 1 or 2 years.
Often they had heavy clubroot infestation, so that's putting tremendous selection pressure on the pathogen to adapt to the new resistance.
If one could move out of such a short rotation, particularly where clubroot is prevalent, it reduces pressure and will help to ensure the longevity of that resistance," he said.
Strelkov notes the issues of broken clubroot resistance have only been documented in Alberta at this point.