If we asked you to list some of the most common fungal diseases for Australian wheat, chances are yellow spot and septoria nodorum blotch (SNB) are amongst the list.
There’s a lot about them we don’t like, including the economic impact they have and their crafty ability to resemble one another, which can prove to be quite the headache for researchers and growers alike.
So this is what we do know about these devilishly deceptive pathogens:
- Both infect the same host – wheat
- They share certain characteristics – both are stubble-borne, they flourish in similar growth environments (i.e. cool, humid conditions)
- The symptoms can often be difficult to tell apart visually
- Both are on the CCDM hit list
Previous research has already shown us that somewhere along the way of evolution, these two fungi have exchanged DNA, meaning one has taken up genetic materials of the other, allowing them to cause similar disease symptoms, making their diagnosis a lot more difficult.
So similar are they that even though growers and researchers have widely accepted that this troublesome duo actually co-exist, researchers have lacked the tools to simultaneously detect and quantify their presence or abundance.
Researchers at the Centre for Crop and Disease Management (CCDM) – a national research centre co-supported by Curtin University and the Grains Research and Development Corporation (GRDC) – have been putting their detection skills to the test, coming up with a high throughput quantification tool that is able to provide the diagnostic evidence that the pathogens for yellow spot and SNB do in fact co-exist when infecting wheat leaves.
Researchers compared a series of methods for diagnosing these diseases using multiple lab-based experiments with DNA from both fungi, and then progressed to naturally-infected wheat leaves collected from a farm site at Muresk in Western Australia.
The field samples all indicated typical yellow spot symptoms present in the leaves. However, when researchers tested the same naturally infected wheat leaf samples using their newly developed diagnostic method, in all cases the collected samples not only reconfirmed the yellow spot symptoms but showed signs of the presence of SNB as well. This was later shown to be consistent across multiple field sites.
CCDM PhD student Araz Abdullah undertook the testing, as part of his PhD research program. He says that by building on previous testing methods using quantitative Polymerase Chain Reaction (qPCR) technology, they developed a unique system where they were able to tag each pathogen DNA sequences with differentially fluorescing probes.
This allows both pathogens to be seen at the same time, but on different channels on the PCR machine – importantly marking the first time they’ve been able to detect, and quantify, these two fungi at once.
The research team also tested the method on samples that had very low presence of one disease, but with abundant presence of the other, to ensure that both diseases can be quantified even at low levels.
So what does this mean?
By enabling researchers to break down the relative contribution of each pathogen to the total infection in a sample, this new tool will allow more targeted testing, giving a clearer understanding of which pathogen is more prevalent across the season on different wheat varieties.
The testing is also expected to help us better understand how these pathogens interact when infecting wheat, and how best to then manage that interaction.
By putting this new method to use, researchers and industry will be able to work together to develop more effective management plans or strategies to tackle these diseases.
The research was recently published in Frontiers in Plant Science, with the full paper available online here.
The research team included the CCDM’s Araz Abdullah, Dr Ayalsew Zerihun, Dr Caroline Moffat, Chala Turo, Dr Fran Lopez-Ruiz, and Professor Mark Gibberd, with collaboration from UWA Institute of Agriculture’s Professor John Hamblin.
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