September 11, 2005
From: FinFacts Business News, 8 Sep 2005 [edited] <http://www.truthabouttrade.org/article.asp?id=4400>

New strain of wheat rust appears in Africa

Biologists warned Thursday [8 Sep 2005] that a virulent new strain of a previously controlled plant disease had emerged in East Africa and could wipe out 10 percent of the world's wheat production if its spread is not halted.

The fungus that causes wheat stem rust (WSR), _Puccinia graminis_ f. sp. _tritici_, produces a rusty color on wheat stems and slowly destroys the plant. It was controlled in the late 1950's and 1960's through the groundbreaking work of Norman Borlaug, an American who won the Nobel Peace Prize in 1970 for developing high-yield grains that led to the green revolution. Dr. Borlaug, now 91, spoke at a news conference on Thursday [8 Sep 2005] in Nairobi and called attention to the new threat. "Nobody's seen an epidemic for 50 years, nobody in this room except myself," he said. "Maybe we got too complacent."

After the new WSR strain fungus emerged -- named Ug99, for Uganda 1999 -- it seemed to disappear for a couple of years. It re-emerged in Kenya in 2001 and in Ethiopia 2 years later, said Ravi Singh, a plant pathologist
with the International Maize and Wheat Improvement Center (CIMMYT), a nonprofit research group that convened an expert panel to study the resurgent disease. The panel's report, to which Dr. Borlaug contributed,
was released at the news conference.

"It's spreading, and that's why we're sounding the alarm now," Dr. Singh said. WSR spreads by wind-borne spores or on the clothing of travelers. The panel's report warns that urgent action is needed if the world's wheat
producers are to be spared. A 10 percent reduction in global wheat yield would mean a crop loss of 60 million tons, worth USD 9 billion, said Ronnie Coffman, chairman of the panel and a professor of plant breeding and
genetics at Cornell University.

"It is only a matter of time before Ug99 reaches across the Saudi Arabian peninsula and into the Middle East, South Asia and, eventually, East Asia and the Americas," the report said.

A Global Rust Initiative has been set up in Nairobi to monitor the progress of the disease and begin the process of breeding and disseminating new resistant wheat varieties. In the 1950's, wheat rust devastated crops in North America, affecting 3/4ths of some varieties. Since then, scientists have worked to develop high-yielding varieties that resist ever-emerging diseases.

Wheat grown in East Africa had been resistant to the disease for the last 40 years. But the new strain has decimated local varieties.

Industrial farmers grow most of Kenya's wheat, and they have been spraying their crops several times a year to control WSR. But wheat rust could have a devastating effect in countries like Ethiopia and India, where local farmers grow the bulk of the wheat, and chemicals might prove too costly. Dr. Masa Iwanaga, the Director-General of CIMMYT, said his organization had compiled 165 000 different genetic varieties of wheat over the years, giving scientists a head start in searching for strains resistant to the new variety.

[Byline: Marc Lacey]

--
ProMED-mail
<promed@promedmail.org>

[The origin of strain Ug99 was not unexpected. Evolution of new strains of pathogens is a constant process, and the arrival of a new strain, Ug99, presents a challenge to wheat producers worldwide. The new strain was detected in a test group of about 30 percent of experimental wheat lines growing in Uganda, a "hot spot" notorious for rust diseases. The concern is that spores of Ug99 are undoubtedly destined to reach susceptible wheat cultivars in the Saudi Arabian peninsula and the Middle East, South Asia and, eventually, East Asia and the Americas. Wheat cultivars grown in East Africa have remained resistant to WSR for the past 40 years, but Ug99 has decimated local cultivars. WSR occurs wherever wheat is grown, and yield losses can range up to 70 percent over a large area, and infected fields can be totally destroyed. Damage is greatest when the disease becomes severe before the grain is completely formed. In areas favorable for disease development, susceptible cultivars cannot be grown. Grain is
shriveled due to the damage to the conducting tissue, resulting in less nutrient being transported to the grain. Severe disease can cause straw breakage, resulting in a loss of wheat spikes during combine harvesting.

Links:
<http://www.cdl.umn.edu/> <http://www.planetark.com/dailynewsstory.cfm/newsid/32441/story.htm>
<http://www.finfacts.com/irelandbusinessnews/publish/article_10003193.shtml>
- Mod.DH]

[see also in the archive:
2002
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Wheat stem rust fungus, new virulence genes - So Afr 20020814.5049 2000
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Wheat stem rust in resistant wheat lines - Uganda (02) 20000713.1162 Wheat stem rust in resistant wheat lines - Uganda 20000702.1092 1999
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Stem-rust fungus, mutant, wheat - Uganda 19990519.0812]

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