EL BATAN, Mexico and ALEPPO, Syria, -- 16 Jan 2007 -- A new form of stem rust, a virulent wheat disease, has jumped from eastern Africa and is now infecting wheat in Yemen in the Arabian Peninsula.
Researchers with the Global Rust Initiative (GRI) and the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) have confirmed conclusively the existence of the disease in Yemen. There is also evidence that the disease has spread into Sudan but more tests are needed to confirm the finding. Until this discovery, this new strain of stem rust, known as Ug99, had only been seen in Uganda, Kenya and Ethiopia.
The last major epidemic of stem rust occurred in North America in the early 1950s, when a strain of stem rust destroyed as much as 40 percent of the continent's spring wheat crop. Out of this crisis came a new form of international cooperation among wheat scientists worldwide, spearheaded by Nobel laureate wheat scientist Norman Borlaug. This international alliance of scientists led to the development of wheat varieties which resisted the onslaught of stem rust for more than four decades. But in 1999, a new strain of stem rust was discovered in Uganda and Kenya capable of destroying most previously disease-resistant wheat varieties.
A year and a half ago geographic information systems specialists working at CIMMYT plotted the probable trajectory of the fungus, whose spores can travel large distances on the wind. The wind models predicted that if the fungus crossed from eastern Africa to the Arabian Peninsula it could easily spread to the vast wheat-growing areas of North Africa, the Middle East, Pakistan and India.
There is precedence for this, from a virulent strain of another wheat disease, called yellow rust, which emerged in eastern Africa in the late 1980s. Once it appeared in Yemen, it took just four years to reach wheat fields of South Asia. On its way, this new strain of yellow rust cau
Contact: David Mowbray
International Maize and Wheat Improvement Center (CIMMYT)