Wheat stem rust can attacks mostly the stem, leaves and inflorescence of plants. Wheat stem rust risks Australia’s $6 billion grain crop.

Scientists might have had a breakthrough in the battle against a threat which could decimate Australia’s valuable wheat crop.

Researchers are developing wheats capable of resisting a new strain of rust disease which risks huge losses to Australia’s $6 billion annual grain crop.

Wheat stem rust can attack all above-ground parts of the plant, including the stem, leaves and inflorescence.

Infected wheat plants may also produce shrivelled grain, while an untreated infection could reduce grain yield by up to 90 per cent.

The new strain Ug99 (found in Uganda in 1999) is a virulent strain of wheat stem rust first detected in Africa and the Middle East that has overcome 17 out of 34 stem rust resistance genes found in wheat.

Around 30 per cent of current wheat varieties are susceptible to the Ug99 strain, and scientists are working to ensure Australian crops are protected against the disease.

Ug99 has not been detected in Australia, but an outbreak could cost the industry up to $1.4 billion over a decade, according to the CSIRO.

A previous major stem rust outbreak in Australia in 1973 affected crops across four states and cost the wheat industry between $1.8 billion and $2.7 billion (in 2014/15 dollars).

Desperate to avoid a Ug99 outbreak, scientists are working to develop wheats with a stronger and potentially more durable level of resistance by “stacking” five resistance genes together.

Researchers combined and inserted five different wheat resistance genes to make it much harder for rust pathogens to attack wheat successfully.

“Our approach is like putting five locks on a door – you’re making it very difficult to get in,” Lead CSIRO researcher Dr Mick Ayliffe said.

“Rigorous field testing showed that our gene stack approach provided complete protection against the rust pathogens we were targeting.”

Dr Ayliffe said the approach could be used globally to protect crops.

“This promising gene stacking technology is a way we could rust-proof not only Australia but international crops as well,” Dr Ayliffe said.

“It’s a valuable insurance policy in case we face mutations in wheat rust with catastrophic virulence, with the ability to deploy long-lasting solutions to the field much sooner than we would have in the past.”

Wheat provides around 20 per cent of the world’s calorie intake, making crop protection vitally important for world food security, with cereal rusts also affecting barley, oats, rye and triticale crops.

Dr Ayliffe said the international study had targeted stem rust. Still, the same technology can breed against stripe and leaf rust diseases as well, and in different existing wheat varieties to add resistance.

Wheat rust can rapidly mutate, making it difficult for wheat breeders to respond quickly using conventional breeding.

The disease spreads from plant to plant by spores, which are small, light, and survive for several days.

In addition to being spread by wind, spores can easily attach to clothing, machinery and tools allowing movement and spread between farms and regions.

Adoption of this new in-built resistance technology would also be a valuable tool for integrated pest management, lowering the need for fungicides and increasing the durability of the management tools for farmers.

Originally published at 7 News