In collaboration with
Marcroft Grains Pathology and Syngenta
Blackleg is the most damaging disease of canola crops in Australia, costing the industry millions of dollars annually. The disease is caused by the fungal pathogen Leptosphaeria maculans and primarily inflicts yield losses by restricting the uptake of nutrients and water at the crown of the stem and causing the plant to wilt and canker.
There are several important factors which influence the severity of the damage caused by the pathogen on a canola crop. These include climate, crop rotations, time of sowing, and fungicide applications.
To explain more about Blackleg and the best practices for managing it in your growing conditions, we’ve put together some helpful videos with the assistance of Dr Steve Marcroft from Marcroft Grains Pathology. You’ll also hear from our Regional Market Development Managers – Michael Hickey from Western Australia and Adrian Carter from Eastern Australia – as they explain how we manage Blackleg genetics in our canola varieties.
Blackleg genetics and major gene resistance
Major genes offer complete resistance against a range of difference strains of the Leptosphaeria maculans pathogen. In Australia, canola cultivars are assigned a blackleg resistance group based on their specific combination of major resistance genes. Several major genes have been identified through years of research and are an essential staple of the Australian canola industry.
However, major genes are prone to break down over-time as the pathogen evolves and adapts to overcome the single gene. This is where minor gene resistance, also known as quantitative resistance, becomes a critical component of the overall resistance package.
In this video:
- Dr Steve Marcroft: how major gene resistance works
- Adrian Carter: how growers should use Blackleg groupings
- Michael Hickey: how Nuseed manages Blackleg in our canola varieties
Quantitative resistance and Blackleg ratings
Quantitative or minor gene resistance can be influenced by a number of different regions or genes within the Brassica napus genome and has garnered recent attention as a potential target for molecular markers and a viable way to increase the base resistance of canola cultivars.
Individually, minor genes offer only moderate resistance against blackleg disease. However, the combination of several minor genes together in one cultivar could significantly minimise the plant deaths and yield losses caused by a blackleg infection. Importantly, due to its multi-gene basis, minor-gene resistance possesses increased complexity.
This complexity is much harder for the pathogen to overcome and therefore confers sustained resistance across many years. It may also increase the longevity of major genes if combined within the same cultivar.
In this video:
- Dr Steve Marcroft: quantitative resistance & Blackleg ratings
- Adrian Carter: how Nuseed tests Blackleg genetics in our canola varieties
Blackleg ratings and the use of fungicides
The GRDC operates a number of disease nurseries across all 4 canola growing states in Australia in order to determine their independent Blackleg ratings. Canola growers can use those ratings to help determine the most effective fungicide program for their growing conditions.
Refer to the GRDC Blackleg Management Guide to learn more about these ratings and what they mean.
In this video:
- Dr Steve Marcroft: how Blackleg resistance ratings are assigned, and the role of fungicides in Blackleg Management
Blackleg is an ongoing and evolving challenge for everyone in the canola industry. However, advances in molecular biology and biotechnology are helping fast-track the development of canola varieties with novel and improved resistance.
Plant breeders and researchers such as those at the Nuseed Innovation Centre (NIC) in Horsham have a critical role to play through the development and release of canola cultivars with superior and long-lasting blackleg resistance packages.
Our canola varieties go through a rigorous Blackleg screening process, and all Nuseed canola seed is protected against early season disease and insects through the use of seed treatments, such as Saltro® Duo from Syngenta.
