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Genetic technique leads industry closer to disease resistant wheat

Media release

Researchers from the Centre for Crop and Disease Management (CCDM) have taken further steps towards developing wheat varieties with improved resistance to disease, after a recent study ‘deleted’ three disease-causing genes in a strain of fungus.

The fungus Parastagonospora nodorum is a highly destructive pathogen that causes septoria nodorum blotch on wheat. It is responsible for reducing wheat yields by 10 to 20 per cent across the Australian agricultural industry despite the application of fungicides and a heavy focus on plant breeding over the past 30 years.

Dr Kar-Chun Tan and his team of the CCDM, an initiative co-funded supported by Curtin University and the Grains Research & Development Corporation (GRDC), was able to uncover evidence of new ‘effectors’ – proteins secreted by the fungus that cause disease symptoms – by deleting genes that code for the three currently-identified effectors: ToxA, Tox1 and Tox3.

Dr Tan said the triple gene knockout mutant strain still infected wheat without the three major effectors, albeit at a reduced level.  The removal of the three known major effectors allow researchers to focus of processes that are otherwise difficult to delineate.

“This research is significant because it has shown that there are other key effectors that are killing the leaf tissue besides the major three we know of,” Dr Tan said.

“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 ultimate breeding tool to breed disease resistant wheat.”

Dr Tan said his research team regularly supplied effectors to breeding organisations to help breeders reproduce wheat without susceptible disease genes.

Effector proteins can be directly infiltrated onto a wheat leaf, and in a matter of days breeders can see if the wheat carries the susceptible gene by the presence of leaf damage.

“The team also supplied genetic markers that can pinpoint the approximate location of genetic resistance within wheat germplasms,” Dr Tan said.

“As more effectors are discovered, we anticipate new genetic markers to become available to breeders.

“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. I’m pretty proud to see my research team make such a difference to Australian growers.”

This technology is being developed for other necrotrophic diseases studied at the CCDM, including yellow spot of wheat, net blotch of barley and ascochyta blight of pulses.

Breeding companies are encouraged to contact Dr Kar-Chun Tan for effectors, genetic markers or for more information on 08 9266 9916; kar-chun.tan@curtin.edu.au

The paper, titled Functional redundancy of necrotrophic effectors – consequences for exploitation for breeding, can be found at http://journal.frontiersin.org/article/10.3389/fpls.2015.00501/abstract