A STUNNING breakthrough by South Australian and German researchers into disease resistant barley may help find new ways to protect all crops.
Cereal researchers from the University of Adelaide in partnership with a team at Germany’s Leibniz Institute have overturned 40 years of research to unlock the development of new lines of barley resistant to powdery mildew.
Although the absolute earliest Australia’s croppers can expect to benefit in the paddock is five years, the breakthrough is pointing researchers around the world down new pathways in areas from wheat to grapevines.
Senior research scientist Dr Alan Little says there is a real possibility it may eventually provide a key to the challenge of rust in wheat – Australia’s number one disease threat in the cereal industry.
“Powdery mildew is a significant problem wherever barley is grown around the world”
Dr Little and his team have discovered the composition of special growths on the cell walls of barley plants that block the penetration of the fungus into the leaf.
He says powdery mildew – one of the most damaging of barley diseases – feeds on the living plant.
“The fungus spore lands on the leaf and punches its way through cell walls and taking the nutrients from the plant,” he says.
“The plant tries to stop this penetration by building a plug of cell wall material – a papillae – around the infection site. Effective papillae can block the penetration by the fungus.
A cross section of a barley leaf (blue) showing the formation of a papilla in response to fungal infection. Both the fungal appressorium and the papilla are label with a callose specific antibody (green).
“But using new techniques, we’ve been able to show in the papillae that block fungal penetration, two other polysaccharides are present in significant concentrations and play a key role.
“It appears callose acts like an initial plug in the wall but arabinoxylan and cellulose fill the gaps in the wall and make it much stronger.
“For the past 30 or 40 years we have been aware of these components but never fully grasped their potential – it has long been thought callose is the main polysaccharide component of papilla.”
The discovery gives researchers new targets for breeding powdery mildew resistant barley lines.
Dr Little says from here genetic markers can be developed and used with conventional or modern breeding techniques to identify more resistant lines.
“Powdery mildew is a significant problem wherever barley is grown around the world,” Dr Little says.
“In recent times we’ve seen resistance in powdery mildew to the class of fungicide most commonly used to control the disease in Australia so barley with improved resistance to is now even more important.”
A scanning electron microscope image of a fungal haustorium (Blumeria graminis f. sp. hordei) taken from inside the barley epidermal cell.