Wheat Stem Rust: Heading Off World Wheat Threat

The fungal strain was named for its discovery in Uganda in 1999.

The disease spreads by wind-blown fungal spores. Planting highly resistant wheat varieties in the southern United States where stem rust fungus can survive winter could prevent the disease from taking hold in the South and then spreading to the rest of the country.

Ug99 has overcome most of the stem rust resistance genes bred into wheat varieties during the past several decades. Last year, ARS Cereal Disease Laboratory (CDL) plant pathologist Yue Jin confirmed a new, even more virulent variant of Ug99 in Kenya. His colleague, geneticist Les Szabo, also at the CDL in St. Paul, Minn., leads the stem rust genome project.

The CDL is the nation's primary facility for identifying various forms of stem rust and other cereal rusts, such as wheat leaf rust and oat crown rust.

Jin and Szabo are part of a team of ARS scientists in laboratories across the United States working with breeders to put resistance genes into wheat and barley varieties. They rely particularly on four ARS regional small-grains genotyping laboratories for their capacity to search for breeder-friendly DNA markers for locating resistance genes.

Nationally, ARS scientists and university cooperators have planted susceptible and resistant wheat varieties at various locations around the country to watch for new rust strains.

Internationally, ARS provided funds and expertise to the Global Rust Initiative formed in 2005 by two international organizations to fight the new strain of the disease.