Crop and Pasture Science Crop and Pasture Science Society
Plant sciences, sustainable farming systems and food quality
RESEARCH ARTICLE (Open Access)

Insights into fighting against blackleg disease of Brassica napus in Canada

Xuehua Zhang A and W. G. Dilantha Fernando A B
+ Author Affiliations
- Author Affiliations

A Department of Plant Science, University of Manitoba, 66 Dafoe Road, Winnipeg, MB, R3T 2N2, Canada.

B Corresponding author. Email: Dilantha.Fernando@umanitoba.ca

Crop and Pasture Science - https://doi.org/10.1071/CP16401
Submitted: 25 October 2016  Accepted: 15 June 2017   Published online: 15 August 2017

Journal Compilation © CSIRO Publishing 2017 Open Access CC BY-NC-ND

Abstract

Blackleg disease, caused by the ascomycete fungal pathogen Leptosphaeria maculans, is a devastating disease of canola (Brassica napus) in Australia, Canada and Europe. Although cultural strategies such as crop rotation, fungicide application, and tillage are adopted to control the disease, the most promising disease control strategy is the utilisation of resistant canola varieties. However, field populations of L. maculans display a high evolutionary potential and are able to overcome major resistance genes within a few years, making disease control relying on resistant varieties challenging. In the early 1990s, blackleg resistance gene Rlm3 was introduced into Canadian canola varieties and provided good resistance against the fungal populations until the early 2000s, when moderate to severe blackleg outbreaks were observed in some areas across western Canada. However, the breakdown of Rlm3 resistance was not reported until recently, based on studies on R genes present in Canadian canola varieties and the avirulence allele frequency in L. maculans populations in western Canada. The fact that Rlm3 was overcome by the evolution of fungal populations demands canola breeding programs in Canada to be prepared to develop canola varieties with diversified and efficient R genes. In addition, frequent monitoring of fungal populations can provide up-to-date guidance for proper resistance genes deployment. This literature review provides insights into the outbreaks and management of blackleg disease in Canada.

Additional keywords: avirulence, Leptosphaeria maculans, resistance.


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