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This study is still in progress but it aims to create a better understanding of the pathosystem, and instill new discussions aiming for more efficient blackleg management that serves in the best interests of canola growers in western Canada.
Project Summary
Background
Blackleg, mainly caused by the fungus Leptosphaeria maculans, is the most serious disease of canola (Brassica napus) worldwide. In western Canada, strategies such as selecting resistant (R) varieties, R gene rotations, and longer rotations with non-host crops, early flea beetle control and the newly implemented fungicide seed treatments are currently used in restricting blackleg disease.
Environment plays a major role in determining a disease (i.e. disease triangle). The nature of spores liberated, the spore movement and infection, are all part of this and a thorough understanding is required to mitigate any crop disease. Interactions between the type of spores of the pathogen (blackleg fungus) and canola varieties in the Prairies is (especially) unknown. Pycnidiospores (asexual spores) are believed to be the major inoculum source causing blackleg disease of canola in western Canada. However, there is lack of understanding in relation to how pycnidiospores and ascospores (sexual spores) will interact with existing canola varieties (R and MR) in western Canada. In addition, there is a knowledge gap in the efficacy of fungicide seed treatments in confronting these different types of spores to mitigate the disease to economical levels. Seed treated fungicides are a new class of fungicides for Canada.
This proposed research targets to address this knowledge gap by conducting a three-part research project that scrutinizes interactions of ascospores and pycnidiospores with blackleg resistance in canola and efficacy of seed applied fungicides in these specific interactions in western Canada.
Purpose
This study will improve the understanding on the pathosystem, especially how ascospores and pycnidiospores may interact with blackleg resistance in existing canola varieties. Information from the study can help growers to make decisions on using varieties carrying specific R genes. If nonspecific resistance plus a fungicide seed treatment can be sufficiently effective against both inoculum types, growers may not have to rotate their varieties frequently. It will provide a new angle to manage blackleg more efficiently when both ascospores and pycnidiospores are present.
Objectives
The objectives of this study are to:
- Develop a protocol to efficiently produce ascospore and pycnidiospore inoculum with defined Avr profile for inoculation of canola seedlings in research and resistance screening by industry;
- Assess potential interactions of inoculum types (ascospores and pycnidiospores) with blackleg resistance (major and minor);
- Evaluate the efficacy of seed applied fungicides against the infection by ascospores and pycnidiospores influenced by genetic resistance.
