Fungal disease reveals multiple chemical defence
GroundCover™ Issue: 123 | Author: Dr Gio Braidotti
The cause of septoria nodorum blotch on wheat, Parastagonospora nodorum, can reduce wheat yields by 10 to 20 per cent despite the application of fungicides and a heavy focus on plant breeding over the past 30 years.
Researchers from the Centre for Crop and Disease Management (CCDM) at Curtin University believe they are close to understanding why the fungal disease septoria nodorum blotch persists in being so damaging despite all chemical and breeding efforts.
In a project co-funded by the GRDC, team leader Dr Kar-Chun Tan and colleague Dr Huyen Phan used gene technology to get a glimpse into the fungus’s genome and discovered a far more potent arsenal of disease-causing ‘effector’ genes than previously known.
Dr Tan reports that his team, particularly through the efforts of Dr Phan, was able to delete the genes that code for the three known effectors: ToxA, Tox1 and Tox3. Despite missing the ability to make and secrete the encoded proteins, the mutant fungal strain still retained the ability to infect wheat. The only real impact from the triple gene knockout was a lower infection rate.
“This research is significant because it shows there are other ‘effectors’ that are killing the leaf tissue besides the major three we know of,” Dr Tan says. “It is also well documented that wheat germplasm contains susceptibility genes that respond to particular effectors. If we can find all these effectors, and the corresponding susceptible genes within wheat, then this could become the tool to breed disease-resistant wheat.”
Dr Tan has developed DNA markers that pinpoint the approximate location of genetic resistance within wheat germplasm.
“As more effectors are discovered, we anticipate new genetic markers becoming available to breeders,” he says.
“Already by providing the option of effectors and markers to breeders, we have helped breed wheat with much better disease-resistant profiles, which has saved the industry millions of dollars through improved yields.”
More information:Dr Kar-Chun Tan,
08 9266 9916,
GRDC Project Code CUR00023