June 13, 2011


Wheat fungus invades Middle East and Africa



A devastating wheat fungus is active in 11 countries in Africa and the Middle East, according to scientists striving to develop resistant varieties before the fungus can attack fields around the globe.


Up to 90 % of the world's wheat is susceptible to the strain of stem rust, called Ug99, first detected in Uganda in 1999. The oval, brick-red lesions of stem rust sap wheat plants and cut yields by 50-70 % over wide areas and can destroy entire fields.


Ahead of a meeting of scientists next week in St. Paul, Minnesota, researchers said they are close to producing rust-defeating varieties that also boost yields. Wheat is the most widely grown food grain in the world and is second only to rice as a food staple.


"We're pretty confident," said Ronnie Coffman of Cornell University, of endowing wheat with three or four genes that resist rust, a virtually unbeatable combination. Still, it can be years, even a decade, before resistance can be transferred into local varieties and grown widely.


The new varieties would not be genetically modified. Wheat growers have resisted using GMO seeds because of consumer concerns, especially in Europe.


Meanwhile, the wind-borne Ug99 fungus could continue to spread, first to South Asia and eventually, said a panel of rust experts in 2005, to East Asia and the Americas.


"I am confident Ug99 is not in South Asia at the moment but it is really only a matter of time," said rust-tracker David Hodson. The fungus is identified in Uganda, Kenya, Ethiopia, Sudan, Yemen, Iran, Tanzania, South Africa, Zimbabwe, Mozambique, and Eritrea.


Ironically, the campaign to avert catastrophic losses threatened by Ug99 stem rust may get a boost from farmers trying to end the smaller but repeated losses inflicted by yellow rust. Also known as stripe rust, the fungus has spread rapidly over the past few years and infected new regions.


"They (farmers) appear willing to change to get something resistant to yellow rust," Coffman said. Coffman is part of a Cornell project that coordinates the fight against stem rust.


Ravi Singh of the International Maize and Wheat Center, based in Mexico, and colleagues from the Kenya Agriculture Research Institute and the USDA, will report at St. Paul on wheat varieties being developed by the center that show strong resistance to the three rusts - stem, stripe, and leaf. Some of them yield 10-15 % more wheat as well.


"We have made tremendous strides on the science side but now we need to see progress on the development side," Singh said. The next steps are to produce large supplies of resistant seeds and foster use of them, and to create jobs performed by national agencies and development groups.


Rust-resistant seed "is the only viable option" for poor farmers because they cannot afford fungicides, said scientists in 2006 when the Global Rust Initiative was beginning work. Otherwise, "stem rust disease could once again become the cause of food shortages and famines in Africa, the Middle East, and Asia if the spread of race Ug99 remains unchecked."


The last major outbreak of stem rust in the US in the 1950s cut the wheat crop in the Northern Plains by 40%, a loss of 70 million bushels.


The campaign to develop new varieties of rust-resistant wheat is budgeted at nearly US$70 million through mid-decade, much of it coming from the Gates Foundation.

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