Protecting canola against blackleg by introducing novel genes and developing R gene specific markers

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This project is still in progress and aims to introduce novel sources of blackleg disease resistance genes and to develop gene-specific markers that will be used as tools for precision breeding of resistant cultivars.

Project Summary

Blackleg disease of canola (Brassica napus) caused by the fungus Leptosphaeria maculans (Lm) occurs in almost all canola growing countries. The disease starts as soon as young canola seedlings emerge from the ground. Lm spores land on the cotyledon and young leaves, germinate and penetrate into the tissue. Early symptoms of the disease include the appearance of greyish lesions with spores seen as black dots on the leaves.

Canola varieties that have resistance (R) genes against blackleg are able to block the pathogen spread at the site of infection. However, in the susceptible canola cultivars, Lm continues to grow and reaches the stem causing crown canker seen as a black lesion at the base of the stem. Stem canker is the main cause of yield losses estimated at 10-15% when disease severity is low and to nearly complete loss of crop on the highly blackleg susceptible canola cultivars1. R genes against blackleg are the best and most effective method to completely protect canola against Lm.

The main goals of this research are to:

  • Introduce novel sources of R genes against blackleg disease.
  • Develop race-specific markers for Rlm and LepR genes in B. napus.

These R genes will provide new sources of blackleg resistance to Canadian farmers. The R gene markers will be used as a tool for precision breeding of resistant cultivars by canola breeders and as a genotyping tool to help canola farmers with selecting the most suitable canola cultivar with matching R genes against the prevalent Leptosphaeria maculans races.

In addition, R gene-specific markers will facilitate the implementation of R gene labelling recently introduced by the Canola Council of Canada. Management of blackleg disease by the deployment of the most suitable R gene based on the regional distribution of Lm races will provide farmers with the choice and flexibility to rotate resistant varieties without risking the breakdown of R genes. These R gene collections will ensure improved yield and quality of canola and lower production cost (due to elimination of fungicide) for the Canadian canola farmers.

Reference

1 YixiaoWang, Stephen E.Strelkov, and Sheau-FangHwang. Yield losses in canola in response to blackleg disease. Canadian Journal of Plant Science. 100(5): 488-494. https://doi.org/10.1139/cjps-2019-0259