Researchers have identified a gene that can help fend off a new devastating strain of stem rust, a fungal disease that is now "at the door of the Punjab region", the breadbasket of Asia. The discovery could help breeders more quickly develop varieties that can resist the deadly pathogens and halt a worldwide wheat epidemic, according to the study published in the journal Proceedings of the National Academy of Sciences.
Wheat and stem rust have been in an evolutionary arms race for more than 10,000 years. In the 1950s, a major epidemic of the disease spread through North America and destroyed up to 40 per cent of the wheat crop, the world's second most important grain next to rice. Since then, scientists have developed rust-resistant varieties to boost wheat's immunity to stem rust. But the pathogens are making a comeback.
A new strain of the stem rust — called Ug99 after it was discovered in Uganda in 1999 — is spreading throughout the region. About 90 per cent of the wheat varieties grown worldwide are susceptible to Ug99, according to the researchers. "Ug99 has expanded to most of the wheat-growing regions in Africa and has crossed the Red Sea to Yemen and Iran," said Jorge Dubcovsky, Professor at University of California, Davis in the US.
"Ug99 is now at the door of the Punjab region — the bread basket of Asia — and identification and deployment of effective resistance genes are critical to mitigate this threat," Dubcovsky added. The researchers identified three different resistance forms of Sr13, a gene from pasta wheat that is effective against Ug99 and another group of virulent stem-rust strains from Yemen and Ethiopia. "We hope that a better understanding of the wheat-rust pathosystem will speed the development of new strategies to control this devastating pathogen," Dubcovsky said.