Pathogen cycle knowledge provides potential for tackling fungicide resistance in wheat SNB

Wheat disease boom and bust cycle discovered in battle against resistance

Diseases
Centre for Crop and Disease Management (CCDM) research fellow, Dr Huyen Phan, says researchers have discovered a low amplitude 'boom and bust' cycle in the Septoria nodorum blotch (SNB) pathogen population following the introduction of more resistant varieties. PHOTO CCDM

Centre for Crop and Disease Management (CCDM) research fellow, Dr Huyen Phan, says researchers have discovered a low amplitude 'boom and bust' cycle in the Septoria nodorum blotch (SNB) pathogen population following the introduction of more resistant varieties. PHOTO CCDM

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Latest research uncovers a disease cycle that could hold the key to managing SNB.

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Latest research, led by the Centre for Crop and Disease Management (CCDM), has uncovered a 'boom and bust' pathogen cycle that may be the key to developing new and improved management strategies and disease ratings for the damaging wheat disease Septoria nodorum blotch (SNB).

Using a statistics-based method, the research team from CCDM - a national research centre co-supported by Curtin University and the GRDC - observed evidence of a distinct genetic structure in Western Australian isolates of the SNB pathogen collected over a 44-year period from 25 wheat growing sites in WA.

They grouped the isolates into five clusters based on genetic similarity and, through analyses of their collection year, were able to track the pathogen's emergence and prominence.

Access to such a large pathogen collection is extremely rare, so until now worldwide studies of the evolving SNB pathogen have been limited by a narrow sampling timeframe.

Full results from this research can been found in the paper 'Low amplitude boom-and-bust cycles define the septoria nodorum blotch interaction', available in the Frontiers in Plant Science journal.

Pathogen behaviour

CCDM research fellow and the paper's lead author, Dr Huyen Phan, says the team discovered a low amplitude 'boom and bust' cycle in the SNB pathogen population following the introduction of more resistant varieties.

"Our research team identified many cases where the SNB resistance of wheat varieties declined over successive seasons, prompting their replacement with new and more resistant varieties - only to see the resistance of the older varieties begin to improve," Dr Phan says.

"This change in resistance often coincided with the mass adoption of popular wheat varieties and a shift in the pathogen population."

CCDM senior research fellow and paper co-author Dr Kar-Chun Tan, says this is valuable information for the Australian grains industry looking to maximise disease resistance in current wheat varieties.

"Breeders are doing a great job releasing wheat varieties with improved resistance to SNB, but as our research shows, we're dealing with an ever-evolving pathogen," Dr Tan says.

"The best we can hope for is to find strategies to help prolong SNB resistance in modern wheat varieties."

Dr Tan says the research indicates that diversity in varietal selection and regularly rotating wheat varieties may be good strategies growers can adopt to limit the build-up of specialised and highly aggressive isolates of the SNB pathogen.

Impact on disease ratings

The research also suggests that the testing of modern isolates of the pathogen makes for more accurate SNB resistance ratings of commercial wheat varieties.

"Genetic markers are now available to help identify relevant modern isolates," Dr Tan says.

CCDM Director Professor Mark Gibberd says research such as this has a crucial role in helping the Australian grains industry achieve better disease resistance.

"Fungal pathogens are highly complex, so we need to understand the mechanisms behind their impact and how they evolve, so that we can improve disease resistance," he says.

"The challenge is.then to develop effective management strategies for their control, whilst also working to provide stronger preventative measures by working with breeders to help create more resistant varieties."

GRDC Research Code CUR00023

More Information: Carole Kerr, CCDM, 0437 538 541, carole.kerr@curtin.edu.au

Useful Resource: Full results from this research can be found in the paper - 'Low amplitude boom-and-bust cycles define the Septoria nodorum blotch interaction' available in the Frontiers in Plant Science journal.

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