Stripe rust ‘devastating’ wheat crops worldwide

Global - rust TD Farm
ABOVE: Early stages of stem rust symptoms on wheat. (Photo: USDA)

THE first major resistance genes have been isolated for stripe rust disease that is devastating wheat crops worldwide.

The breakthrough by Australian and British scientists in cloning three related rust resistance genes called Yr7, Yr5, and YrSP will allow the genes to be integrated into breeding programmes in the fight against pathogens that could kill 70 per cent or more of wheat crops.

Wheat rust is one of the most widespread devastating diseases and stripe rust is the most problematic because it easily adapts to different climates and environments, and there are not many effective genes breeders can use.

The University of Sydney’s cereal rust research team created mutation populations in 2015 and identified mutants for each gene.

Unknowingly in parallel, sc-ientists at the John Innes Centre and the National Institute of Agricultural Botany in the UK were working on two of the genes.

They found out about each other’s work and started collaborating.

“This work finally resolves the relationships between these three genes and has provided an answer to a question that is more than 30 years old,” University of Sydney researcher Peng Zhang says.

“Our work represents the first authenticated molecular isolation of major resistance genes against stripe rust.”

Zhang says the breakthrough could make possible the editing of genes rendered ineffective to the rust pathogen. This could switch on their effectiveness again as a way of protecting against rust pathogens while minimising the use of fungicide.

“Diagnostic markers have been developed so that these genes can be utilised promptly in wheat breeding programmes around the world,” she says.

The breakthrough comes as the Australian Bureau of Agricultural and Resource Economics and Sciences estimated a nation-wide outbreak of the wheat rust strain Ug99 could cost Australia up to A$1.4 billion (£769.5 million) over 10 years.

Executive director Steve Hatfield-Dodds says this highlights the importance of keeping Australia’s A$6-billion (£3.3 billion) wheat industry free of the wheat disease.

“It is a highly virulent strain of wheat stem rust that has overcome 17 of 34 stem rust resistance genes found in wheat,” he says.

“The Ug99 strain … poses a major risk to the wheat industry in terms of revenue losses and increased production costs, should it arrive in the country.

“Significant work is being done in surveillance, monitoring pathogen populations over time to track potential virulence evolution, and pre-breeding for germplasm resistance.”


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