The war on rust, a cereal killer

A University of Sydney team is fighting a destructive fungi.

Robert Park inspects wheat at the University of Sydney Plant Breeding Institute. Picture: The University of Sydney/ Stefanie Zingsheim

The rust lab at the University of Sydney saves Australian agriculturalists many millions of dollars every year.

Led by Robert Park, director of the Australian Cereal Rust Research Control Program at the university, a team of scientists uses pathology, genetics and pre-breeding to develop breeds of wheat, oats and barley that are resistant to the devastating parasitic fungi known as rust.

“Rust is probably one of the most important groups of plant pathogens,” says Park, who has been researching plant diseases for 40 years. “Especially because they can build up quickly and cause a lot of damage. They produce spores that are spread thousands of kilometres by the wind.”

Over the past 100 years, the rust lab has documented about 15 incursions of exotic wheat rusts from overseas. Park says some have arrived on high altitude winds carrying spores from central and southern Africa. In other cases, the spores have inadvertently been brought in on people’s contaminated clothing.

“These exotic incursions have caused hundreds of millions of dollars in damage and cost to the grains industry,” he says.

At the same time, rusts in Australia continue to evolve. The battle with rust waged by Park and his colleagues is never-ending. “These things mutate and change, and overcome the resistance we’ve put in there; just like bacteria developing resistance to antibiotics,” he says. “We have to stay one step ahead. It’s a bit like an arms race.” The Australian government’s Grains Research and Development Corporation estimates that genetic resistance to wheat and barley alone saves the Australian economy $1.09 billion annually. The co-operation of agriculturalists is crucial, Park says. “If some farmers decide to grow high-yielding but very rust- susceptible varieties, they’re putting sectors of the industry at risk,” he says.

Professor Robert Park inspecting wheat varieties at the University of Sydney Plant Breeding Institute in Camden. Picture: University of Sydney / Stefanie Zingsheim

Much of rural Australia has typically low-yield, low-fertility soils and erratic rainfall, meaning lower and variable yields. Agriculturalists do use fungicides to control rusts and other diseases on their cereal crops, but those add significantly to the cost of production, Park says.

Fungicides, a completely different type of rust control, have also been known to select for other fungicide-resistant fungi, some of which are opportunistic fungal pathogens of animals, including humans.

In recent years, the University of Sydney rust lab scientists discovered the first documented

example of fungicide resistance in a cereal rust.

A third potential weapon is biocontrol, using other organisms against pests (which in the past has occasionally produced spectacular backfires, such as the cane toad). “There are other fungi that parasitise rust,” Park says. “They do kill rust but scaling up has never been shown to be feasible on a commercial scale.”

For many years, Park says, genetics has been the mainstay of rust control. He and his colleagues import germ plasm from different parts of the world: they look for rust resistance in wheats from nations where rust is particularly devastating, such as Kenya. At the same time, they monitor rust pathogens in Australia and investigate the various strains, how they emerge and where they spread.

“We use that information to find sources of genetic resistance in these cereals,” Park says. “We can then incorporate that through selective breeding into new high- yielding varieties of wheat, oats and barley for farmers.”