If the deadly Ug99 stem rust arrived in Australia tomorrow, a significant proportion of the country’s wheat varieties would be susceptible and have no effective resistance to the debilitating disease.
Thankfully, scientists like Dr Ian Dundas from the University of Adelaide’s cytogenetics laboratory are working on preventing this occurring by developing new rust resistant genes to be bred into modern wheat varieties. For several years, he has been investigating wild wheat relatives from around the world to find suitable resistance to stem, leaf and stripe rust in the hopes of successfully transferring that resistance into Australian and international wheat varieties.
To date, his team has already sent at least nine Ug99-effective rust-resistant genes from his Adelaide base to wheat breeders in 14 countries, including Pakistan, Kenya, South Africa, Iran and India, for incorporation into locally adapted breeding lines.
“The best place to find effective resistance genes is in the wild related species which are usually found in Middle Eastern countries,” he said.
“Because grassy relatives of wheat have been growing out in the tough wild environment, only the hardiest and most disease resistant plants survive, however they also possess a lot of weedy characteristics such as low yield and poor quality which make them unsuitable for agriculture. The aim is to incorporate a segment of the alien chromosome into a modern wheat chromosome and to then refine the genes down to only include those with rust resistance.
“When we share a resistance gene with plant breeders, we request that they don’t use any one gene on its own, but rather in combination with another effective stem-rust resistant gene to extend the durability of the resistance effort.”
Dr Dundas explains that the most practical, cost-effective and environmentally friendly way of protecting wheat crops from the rust diseases is through the use of resistant cultivars.
“We cannot afford to be complacent as rust can mutate and evolve and can affect any of the existing wheat varieties,” he said.
“Many growers rely on fungicide for rust control and spray as a matter of course however fungicides will not always be an option. Plant diseases are best controlled preventatively. High yielding and rust resistance must be characteristics developed together in a wheat variety.”
In addition, Dr Dundas explains the importance of global food security and Australia’s role in ensuring the security of food to the poorest nations.
“It is our global responsibility to provide the rust-resistant genes to any country which requests them, ultimately it is in Australia’s interest to prevent these rust diseases entering the country,” he said.
“Rust spores are carried in the wind and on clothing so travellers to Africa could potentially bring the disease back into Australia.
“This is an international problem with an international response. Our stem rust resistant lines are being shared with International researchers with the goal of protecting the food supply of the World’s poorest people.
“Rust is always going to be present and is continually evolving, so the wheat varieties grown need to evolve also to continue to offer resistance.”