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).
Researchers from the CCDM, a national research centre co-supported by Curtin University and the Grains Research Development Corporation (GRDC), worked with European collaborators to discover that the pathogen Parastagonospora nodorum, that causes SNB, evolves over time in response to patterns in wheat variety adoption.
Using a statistics-based method, the research team 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.
CCDM research fellow and the paper’s lead author Huyen Phan, said 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 said.
“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 Kar-Chun Tan, said this was 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. The best we can hope for is to find strategies to help prolong SNB resistance in modern wheat varieties,” Dr Tan said.
“Our 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.
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 said.
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,” Professor Gibberd said.
“The challenge then is 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.”
The full results are available in a just-published paper titled ‘Low amplitude boom-and-bust cycles define the septoria nodorum blotch interaction’ available in the Frontiers in Plant Science journal.
Featured Image: CCDM’s Dr Huyen Phan. Image courtesy of CCDM