Understanding the critical infection window that causes blackleg of canola in western Canada

Project Summary

Purpose

The study investigates the relative importance of cotyledons vs. lower true leaves for blackleg infection. It is also be of interest to understand how quantitative resistance (QR) affects the success of stem infection via cotyledons or lower true leaves. The information may help fine tune the timing of fungicide, including use of seed treatment as a new option.  

Results

The fungus Leptosphaeria maculans can cause blackleg more successfully via wounds on cotyledons than on lower true leaves. Cotyledon infection results in higher disease incidence and severity at canola maturity. Researchers also found that QR, without the direct involvement of major R genes, can reduce infection spread from inoculated cotyledons and lower true leaves to the stem, with substantially reduced levels of blackleg relative to susceptible canola. This demonstrates the value of using QR for the management of blackleg in Western Canada.
The importance of cotyledon infection suggests an opportunity to use seed treatment to manage blackleg. Fluopyram and pydiflumetofen are promising seed treatments.