New strains of clubroot, a disease that can kill canola crops, continue to emerge in Western Canadian fields, according to a recent study by University of Alberta researchers.
A sampling of more than 250 fields in Alberta, Saskatchewan and Manitoba conducted in 2019 and 2020 identified 25 unique clubroot pathotypes, including seven new strains — six of them capable of infecting canola plants bred to resist the disease.
"The findings really underscore how quickly pathotype shifts are occurring and how quickly we are finding new pathotypes. And it is likely we will continue to find new ones," says study lead Keisha Hollman, a PhD candidate in plant science in the Faculty of Agricultural, Life & Environmental Sciences.
Clubroot is caused by a parasite that infests field soil with resting spores that can survive up to 20 years. Canola and related plants such as cabbage that are grown in the infested soil develop tumours on the roots, which block water and nutrient uptake, causing stunted growth, yellowing, wilting and in worst cases, death of the plant.
Listed under Alberta's Agricultural Pests Act, clubroot can cause anywhere from 60 to 90 per cent canola crop yield loss in one of Canada's most valuable cash crops.
An ever-evolving adversary
The disease is continuing to evolve, according to the study.
In 2019 alone, 23 pathotypes were documented in prairie canola fields, showing "the most diversity we have ever found in a single year," Hollman says.
Along with that discovery, the research revealed that more resistance-breaking strains of clubroot are becoming predominant, meaning they are the most commonly found. Of the five most common pathotypes identified in Alberta as of 2020, three overcome genetic resistance.
