Impact of verticillium stripe on canola
Verticillium stripe has garnered more attention recently, potentially due to favourable conditions for disease development. This attention has also identified an information gap on the disease and its impact on Western Canadian canola crops. Verticillium stripe, which affects Brassica plants, has led to devastating crop losses in Europe, but we have limited information on its impact in Canada. However, new research projects are underway to enhance understanding of this disease and how best to manage this emerging pest of concern.
Verticillium stripe in Canada
The Canadian Food Inspection Agency (CFIA) confirmed that the observation of Verticillium longisporum in a Manitoban canola field in 2014 was the first presence of this pathogen in any Canadian field crop. The following year a survey found it in five more provinces, including the Prairies. Disease symptoms were noticed in 2018 and 2019 crop years, and this past growing season some yield losses were actually attributed to the disease.
Verticillium stripe or wilt?
Although the vascular disease was initially referred to as “verticillium wilt”, the name has been changed to “verticillium stripe” to more accurately describe the stem striping symptom caused by the soil-borne fungus. This symptom is often accompanied by the presence of microsclerotia and peeling back of the epidermal layer.
New verticillium stripe research
To better understand this disease, three research projects – which can be found on the Canola Research Hub – have been launched via the Canola Agronomic Research Program (CARP) and the Canadian Agricultural Partnership (CAP) programs.
While final results of this four-year project won’t be available until 2023, the first field trial and three greenhouse experiments have already been completed on the four-year ‘Verticillium Stripe Management’ CARP project, led by Sheau-Fang Hwang and Stephen Strelkov at the University of Alberta.
These and the future experiments/trials are aimed at:
- Examining the relative virulence of V. longisporum and V. dahliae on commercial canola cultivars.
- Determining the effects of growth stage and inoculation techniques on infection.
- Evaluating the effects of disease severity on plant growth and yield at different inoculum concentrations.
The objectives of the ‘Verticillium disease etiology and nursery’ CAP project (which is scheduled to wrap up in 2023), led by Dilantha Fernando at the University of Manitoba, are to:
- Further develop tools for rapid identification of the pathogen in soil.
- Understand the longevity of the pathogen and microsclerotia in soil.
- Establish the endophytic nature of the pathogen in soil.
- Measure the diversity of V. longisporum and its lineage.
- Determine and quantify the relationship and interaction between V. longisporum and L. maculans.
- Develop and utilize a verticillium nursery to provide source materials.
- Understand the yield risk of V. longisporum.
- Foster awareness of the disease for its diagnosis, risks and control.
New research focus
The ‘Genetics and genomics of Brassica-Verticillium interaction’ CAP project, led by Hossein Borhan at the AAFC station in Saskatoon, is focused on:
- Identifying resistance against verticillium in Brassica germplasm.
- Understanding genome organization of Canadian isolates of the V. longisporum pathogen.
- Understanding the biology of V. longisporum virulence and identifying virulence factors in the V. longisporum genome that are vital to colonization of the host.
- Gaining insight into the molecular interaction between V. longisporum and B. napus.
In addition, the industry is working toward finalizing a verticillium stripe disease severity scale and continues monitor the disease spread and levels of infection through provincial surveys.