Africa Sees New Stem Rust Strain

Global Rust Initiative formed to monitor Ug99 strain; genetic resistance identified for every market class of U.S. wheat

The most virulent new strain of wheat stem rust in 50 years, tabbed Ug99, has been identified in Africa, but a Global Rust Initiative hopes to keep the new strain in check.

Kay Simmons, USDA-ARS national program leader for grain crops, presented an overview of the new strain of rust at the recent Grain Congress, the annual meeting of the National Association of Wheat Growers.

Ug99 was first identified in Uganda in 1999, and has since spread to Kenya and Ethiopia. Little resistance to the new strain has been found in India, Pakistan, and China, says Simmons, and preliminary tests show that U.S. wheat varieties could be susceptible, if the strain ever reached this continent.

Simmons says it is common for cereal rust pathogens to overcome genetic resistance. The key is to stay ahead of the game, being vigilant about assessing for vulnerability, monitoring changes in rust pathogens, and persistently breeding for rust disease resistance.

Last spring, the International Maize and Wheat Improvement Center (CIMMYT) along with Nobel Laureate Norman Borlaug initiated efforts to form a Global Rust Initiative, (www.globalrust.org) to prevent a pandemic. Cooperators intend to monitor the pathogen as well as identify and characterize new sources of resistance to stem rust race Ug99.

The cooperative research will help preserve wheat production in developing countries. The research will also result in basic information that USDA -ARS may need some day, should Ug99 ever appear in the United States.

Simmons says the good news in the U.S. is that genetic resistance to Ug99 has been identified for every wheat market class and in the U.S. Small Grains Seed Repository in Aberdeen, Idaho. “We know there is resistance, and can start to breed for it,” she says.