Resistance is the best cure

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Dr Francis C. Ogbonnaya, program manager protection traits

This Ground Cover Supplement outlines the three-pronged approach being taken by the GRDC to:
  • develop cereal varieties with greater resistance to cereal foliar fungal diseases;
  • keep abreast of fungal disease dynamics across the GRDC cropping regions; and
  • develop and extend management packages to control fungal diseases on-farm and prolong the useful life of Australia’s limited fungicide options.

Cultivar resistance is the most sustainable way to manage fungal disease – a principle that guides the GRDC’s ongoing and substantial commitment to finding new genes that confer disease resistance in Australian crop varieties.

The GRDC-funded Australian Cereal Rust Control Program (ACRCP), the Australian Centre for Necrotrophic Fungal Pathogens (ACNFP) and the National Barley Foliar Pathogen Variety Improvement Program (NBFPVIP) are the umbrella groups that together cover all major cereal foliar fungal diseases affecting Australian cropping systems.

Between 2007 and 2011, the research activities of the ACRCP characterised 33 new rust-resistance genes, 20 offering robust seedling resistance and 13 with durable adult plant resistance (APR). Since the 1970s, such resistance genes have been inserted into Australian cereal breeding lines and have been provided to plant breeding programs for development of cultivars with greater rust resistance (Surveillance the key to staying ahead of rust).

The work of the ACRCP also has a substantial impact internationally, sending rust-resistance genes to breeding programs in some of the world’s poorest nations to combat the growing threat of stem and stripe rust pathogens (Wild genes help tame rust pathogen). Research by the ACNFP has been instrumental in dealing with the fungicide resistance that has developed in Western Australian strains of barley powdery mildew (New rusts emerge in the west) and also in unravelling how the Septoria nodorum blotch and yellow spot fungal pathogens operate at a molecular level to cause disease (Fungal diseases foiled at molecular level).

The ACNFP activities and pre-breeding research into yellow spot resistance being managed through the Department of Agriculture and Food, WA (DAFWA), are on their way to developing durable resistance to necrotrophic pathogens – diseases that collectively cost Australian growers an estimated $30 million each year.

The NBFPVIP has documented virulences in the Australian populations of net form net blotch, spot form net blotch, spot blotch and powdery mildew, providing breeders with the knowledge to target resistances that are effective against these virulences. It also established differential sets appropriate to Australia that allow continuous monitoring of pathogen populations into the future. The program has established coordinated national screening of germplasm that allows industry to test breeding lines and sources of resistance against as wide a range of virulences as possible, assisting breeders to develop varieties with resistances that are effective across Australia and across several diseases. Now that the knowledge of the virulences that are present and the machinery for testing lines thoroughly is established, identifying superior resistances and moving these into adapted material can be achieved more rapidly (Multiple disease resistance the holy grail).

At the farm level, the work of plant pathology teams across Australia underpins the effective management and monitoring of cereal foliar fungal diseases. Surveillance work by such teams along with the disease monitoring activities of the ACRCP, ACNFP and NBFPVIP captures the changing dynamics of cereal fungal pathogens. This surveillance work is critical to the maintenance of an accurate disease rating system for Australian cereal cultivars and also drives the search for new resistance genetics and the development of fungal disease management packages.

With only a limited number of fungicides available to Australian growers, fungicide resistance is a constant threat. The GRDC is investing in research to find new fungicides and to extend the life of the few fungicides in use (Limited fungicides raise resistance fears).

Fungicides are just one component of an effective management strategy against disease and do not increase yield or retrieve lost yield if applied after infection is established.

New national GRDC research is developing fungicide decision-support tools based on the highly successful blackspot (field pea) and blackleg (canola) tools developed by DAFWA (Disease tools to lift profits). These tools will help growers make profitable decisions when it comes to fungicide applications and in doing so reduce unnecessary and unprofitable spray applications and extend the life of the limited chemical groups available for fungal disease control.

With wheat and barley foliar fungal diseases costing Australian growers an estimated $550 million* each year in lost yield and control costs, developing ways to reduce the need for fungicides and improve the durability of disease resistance in Australian farming systems will lift grower profits and the sustainability of the Australian cereal industry.

More information:

Dr Francis C. Ogbonnaya, program manager protection traits, GRDC,
02 6166 4500

 

Next:

Packaged genes offer durable resistance

* Murray, G.M. & Brennan, J.P. (2009) The Current and Potential Costs from Diseases of Wheat in Australia and The Current and Potential Costs from Diseases of Barley in Australia.

Region National, West, North, South