Verticillium Stripe - The Disease Management
Term: 5 years ending April 2024
Status: Complete
Researcher: Sheau-Fang Hwang, Stephen Strelkov, Rudolph Fredua-Agyeman, U of A
SaskCanola Investment: $416,760
Total Project Cost: $416,760
Grower Benefits
Soil inoculum of Verticillium longisporum inhibited canola emergence and growth.
Scales for assessing verticillium stripe severity at the seedling (Figure 1) and adult plant (Figure 2) stages in canola were generated. A foundation has been established for more accurate evaluation of host resistance.
Yield losses increased with disease severity, occurred without obvious symptoms under low moisture.
Infection with verticillium stripe exacerbated blackleg infections.
Project Summary
Verticillium stripe has moved into Alberta. Research shows that the disease affects seedling establishment and crop growth before affecting tissues in the stem to reduce yield. Significant yield losses can occur even when symptoms are relatively mild, and the relationship between yield loss and disease severity is described by second-degree quadratic equations. Seedling and adult stage disease look different and new disease assessment scales were developed for both. This will be necessary for determining host resistance.
This research has been an integrated and collaborative approach to addressing the major research priorities around the new disease, verticillium stripe, in Canada. It includes four specific objectives; to measure yield loss, monitor disease development, evaluate canola genotypes resistant to verticillium stripe and determine the interacting effects of verticillium stripe and blackleg.
Yield losses were measured by a) growing plants in micro-plots inoculated at different densities where yield losses were measured on a per-plant basis, and b) growing plants in 6m x 1.5m field plots harvested by small-plot combine. Disease was initiated in lab and greenhouse by root-dip method, while in the field, by sowing seed with grain inoculum. Greenhouse experiments were used to determine interactions between blackleg and verticillium stripe.
In 2020, weather conditions were moister than average in the early growing season and resulted in good disease development in field experiments. In 2021, precipitation was well below average in June and July and resulted in much lower disease development, however yield losses still occurred.
Infection of canola by verticillium stripe in the early stages inhibits crop establishment and growth. Later infection leads to deterioration of the stem and vascular tissues. Yield is more adversely affected as the infections become more severe but yield losses can occur under dry conditions with few symptoms. Plants that were inoculated 3 weeks after seeding using the root-dip method developed the most severe symptoms. Refined methods for the inoculation of V. longisporum on canola are important tools for screening germplasm and evaluating resistance phenotypes. Symptom severity appeared different at seedling and adult plant stages, and infection at both stages affected yield. Accurate assessment of symptom severity will assist at identifying disease resistance. This information will facilitate further research into breeding for resistance to verticillium stripe. Infection with verticillium stripe exacerbated the severity of blackleg in canola crops. Extra measures may be needed to control blackleg where verticillium stripe is present.
Fig. 1 Disease rating scale for canola seedlings infected by Verticillium longisporum, where: 0 = no symptoms; 1 = yellowing of cotyledons; 2 = yellowing and partial necrosis of cotyledons, some reduced growth of first true leaves; 3 = death of cotyledons, seedling stunted; 4 = death of cotyledons, seedling stunted, true leaves yellow; 5 = death of cotyledons, seedling stunted, little to no growth of true leaves; and 6 = seedling entirely necrotic.
Fig. 2 Disease rating scale for adult plants infected by Verticillium longisporum, where: 0 = no symptoms or signs of disease; 1 = some discolouration of main stem, with dark unilateral stripe; 2 = discolouration of main stem, microsclerotia on ≤ 25% of the surface, slight stunting of entire plant; 3 = discoloration of main stem, some shredding of the epidermis, microsclerotia on ≤ 75% of the surface, stunting of entire plant; 4 = stem entirely necrotic and covered with microsclerotia, shredding of the epidermis, plant severely stunted.
Final Report PDF: Verticillium Stripe - The Disease Management