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Ug99 — threat to world’s wheatUg99 — threat to world’s wheat

David Bennett

April 17, 2009

11 Min Read

In recent years, a virulent strain of stem rust called Ug99 has largely overcome resistances bred into the vast majority of the world’s wheat varieties.

Over the last decade, the wind-borne rust has moved east from Africa into Yemen and Iran and is expected to next hit Afghanistan, India and Pakistan. Researchers studying the stem rust say an epidemic would not only cause hunger in the developing world, but could move unstable countries onto even shakier political ground.

If, as the adage goes, man is unable to live on bread alone, he also can’t live without it. Early civilizations developed hand-in-hand with wheat cultivation. Bread wheat is only about 10,000 years old and stem rust has been along for the entire ride.

Archaeological finds in the Middle East have included spores of the rust. Some biblical scholars have interpreted Old Testament references to “blasting winds and blight” to be stem rust. The Romans actually worshipped a god believed to ward off stem rust.

As North American wheat acreage increased in the last 150 years, there were recurring stem rust epidemics. Wheat improvement efforts by Canada and the United States were, in large measure, driven by the need to genetically protect the crop against stem rust.

In the mid-1940s, agronomist Norman Borlaug (who would later receive a Nobel Prize) was sent to Mexico by the Rockefeller Foundation to help develop wheat varieties that were, among other things, stem rust-resistant.

In 1950, Canadian and U.S. scientists doing annual surveys discovered a stem rust race that would later spread across the United States. Although it didn’t reach damaging levels immediately, the race was expected to cause epidemics in subsequent years. And it did: from 1951 through 1953, there were dramatic stem rust epidemics, including the near-annihilation of the U.S. durum crop.

In 1953 alone, 20 percent of North America’s spring wheat was lost to stem rust.

By that time, there had been 40 years of science-based research on both the stem rust pathogen and wheat itself. Using Borlaug’s capacity and contacts, Americans and Canadians began an international effort to initiate international rust nurseries. Their efforts in bundling resistance genes with everything else needed in a wheat variety suppressed the disease for over 50 years.

Then, in 1998, a Ugandan trained by CIMMYT (the International Maize and Wheat Improvement Center), found something interesting in his home country. While not much wheat is grown in Uganda, the researcher located a race of stem rust that had overcome the wheat resistance genes. The race was named Ug99.

Alarmed at the potential of the rust to harm global food security, the Global Rust Initiative — now known as the Borlaug Global Rust Initiative and largely funded by the Bill and Melinda Gates Foundation — was launched in 2005.

Rick Ward, a veteran U.S. agronomist who has worked on stem rust for decades and is currently running the initiative while based at Cornell University, spoke with Delta Farm Press in mid-March shortly before a CIMMYT-sponsored meeting drew 300 researchers from over 40 countries to discuss stem rust. Among his comments:

On the initial find and why Africa is so important…

“CIMMYT, the South Africans and Ugandans reported on this in 2000. At that time, it didn’t get much traction in terms of funding or attention. It was also possible that the (rust) variant was adapted to very specialized conditions to Uganda and wouldn’t spread.

“Well, by 2003, Kenya was having significant epidemics. By 2005, wheat couldn’t be grown in Kenya without fungicides.

“The Great Lakes region of Africa — Rwanda, Burundi, northern Tanzania, Kenya and Uganda — is close to the equator. Many people think that isn’t a wheat region. However, it has high elevation. There are 125,000 hectares — about 300,000 acres — of wheat in Kenya. Any day of the year you can find wheat in a vulnerable stage (between heading and harvest) there.

“One feature of stem rust that’s important is that it’s an obligate parasite. It must have a host and there is no resting stage as with something like fusarium. Head blight in wheat can stay dormant in wheat straw or maize for years. Stem rust, when it generates clouds of spores, must have its spores land on wheat (there are other grass hosts, but there isn’t a lot of spore production on them) at the right growth stage.

“In almost all parts of the world, there is either a dry, warm period between wheat crops or a winter. What’s unique about Kenya and a few other places in the world is there’s no such break.

“I have a photograph of 4-inch-tall wheat that’s heading and a combine cutting wheat — all commercial fields — within 500 meters of each other. You can’t see that in many places.

“Once stem rust takes hold in Kenya, it’s like living in a petri dish. It multiplies continually.”

On research difficulties and stem rust mutations…

“In the field, we can’t work with this strain of rust except where it’s endemic in Kenya and Ethiopia. Uganda doesn’t have enough wheat to focus research on. Working closely with the Kenyan and Ethiopian governments, we’ve jointly established screening facilities, brought the world’s wheat to Kenya and showed empirically that roughly 80 percent of the wheat varieties being planted are susceptible to Ug99.

“In 2005, we knew most of the resistance genes (some 50 are recognized) in wheat were being defeated. This rust race had mutations that rendered it able to thrive on more of the 50 resistance genes than any race ever detected before in almost a century of research.

“That still didn’t show how vulnerable the world is, though. Stem rust has dropped off the radar of almost all wheat breeding programs because it hadn’t been a problem in so long. Breeders must prioritize, especially when faced with limited resources. And there was complacency too — we concede we dropped the ball.

“In 2006, we detected a mutant of Ug99 that knocked out a resistance gene, Sr24. It turned out that gene, if it hadn’t been knocked out, was the one we were most relying on to combat the rust. That pushed the percentage of vulnerability up to 90 percent.

“Another mutant has been found since. So, either this rust race is spawning mutants rapidly. Or, it already had many low-frequency mutants that are now being amplified.”

How the rust moves…

“About 30 years ago, a stem rust strain migrated to Australia from either South Africa or Angola. There have been similar spore-size, wind-borne diseases that have come to the Americas from Africa.

“We predicted (Ug99) would move to Ethiopia from Kenya. It did. We predicted it would jump the Red Sea to Yemen. It did, two years ago. In 2008, it was found in Iran.

“Now that Ug99 is in central Asia, it can migrate north and west into, effectively, the plains and steppes of the former Soviet Union. Kazakhstan and Serbia are huge wheat producers.

“If it moves east, it’ll be in Afghanistan, Pakistan and the rest of south Asia. India is the world’s second largest wheat producer after China. The United States is third.

“It has been historically documented that wind patterns took yellow rust — a disease similar to stem rust — on the same path: from Kenya to Yemen into the Middle East and then moved to (the subcontinent region).

“There’s no evidence Ug99 has spread (east beyond Iran) but we don’t have a great deal of surveillance available. There are so few people looking for this rust. In my opinion, the likelihood of Ug99 having stopped in Iran is almost zero. Almost surely, it’s moved into neighboring countries — maybe Turkey and Afghanistan.”

On the Borlaug Global Rust Initiative set-up…

“The BGRI is an advocacy group that, at its core, is led by the Food and Agriculture Organization (FAO) of the United Nations, CIMMYT, ICARDA — based in Syria after plans to place it in Lebanon were cancelled due to war — Indian officials and Cornell University. The BGRI executive committee includes leaders of agriculture research in the United States, Canada, Australia, Turkey, Kenya, Ethiopia, India and China. That means almost all countries (excepting Russia and several South American nations) that produce 1 million, or more, hectares of wheat are represented.

“The BGRI doesn’t have a bank account, doesn’t give out money. It serves to advocate for rational investments (to fight disease).

“The meeting we’re having is a gathering for people interested in defending world wheat against not only stem rust, but the other rusts, as well. However, Ug99 is the poster child.

“At Cornell, I’m supposed to manage one project that addresses most of the BGRI agenda. That is to fundamentally replace the world’s wheat with resistant varieties, preferably those not vulnerable to one race of rust that can wipe out the world’s wheat crop.

“We’re also creating a rust-monitoring surveillance system. The FAO runs a desert locust monitoring program. Every day of the year, they’re aware of where swarms of locusts are located in the Sahara, Arabian Peninsula or parts of western India. They monitor 20 percent of the earth’s surface.

“We’ve taken that model — national teams going out searching for disease while holding GPS units — for stem rust.

On breeding wheat varieties with resistance to Ug99…

“We must foster an environment where varieties will be taken up easily by farmers. A farmer in India won’t take up a Ug99-resistant variety just because it’s resistant. He probably has never heard of it. The resistant variety needs to be better in yield and other attributes than the current varieties.

“It’s a numbers game, and that means there’s a lot of luck in plant breeding. CIMMYT has had some good luck and extraordinary scientists. There are varieties currently in multiplication in Egypt, Pakistan, India, Bangladesh, Nepal, Ethiopia, Kenya, Iran and other countries. That’s the final stage of the project we’re involved in.”

On Congress funding stem rust research efforts…

“My understanding is Congress did, in the omnibus bill, appropriate $1.5 million this year. The request was for $5 million. Our project costs $9 million annually.

“Dr. Borlaug supplied a letter to the National Association of Wheat Growers in which he endorsed their efforts. It’s hard to tell what the impact was, but my guess is it helped.

“On one hand, that’s good news. On the other, $1.5 million for something so dangerous, something that destroyed 20 percent of the U.S. spring wheat crop in North America, is peanuts. That’s particularly true in the face of writing (Wall Street bailout) checks for $70 billion without knowing exactly where it’ll be spent. It’s pretty frustrating. Dr. Borlaug calls it short-sightedness.”

On the destabilizing potential of Ug99…

“There are two things we focus on. Take Ethiopia — 1.5 million hectares of wheat with the average farm size being 1 hectare. Most of those 1.5 million farmers exist on $1 per day, or less, of family income. If their wheat crops fail, the elderly and babies will be dying. That’s the first concern: the humanitarian costs.

“Many people — although not your readers, I suspect — believe there are years’ worth of wheat and other commodities in storage. When you tell them it’s actually only a couple of months, they ask, ‘How the hell did we get into this situation?’

“It’s a delicate balance we’re involved with here. A major disease that hits yield would have devastating consequences.

“China is also vulnerable. Eventually derivatives of Ug99 will reach China. China and India combined represent over half the world’s population. China, India and Pakistan are three nuclear powers.

“If India’s government is facing dramatic civil unrest because of escalating wheat prices — or they don’t have the wheat — it is unlikely U.S. or Australian wheat will simply be airlifted over. It could take a year to fill a shortfall by diverting ships.

“And only 10 percent of the world’s wheat crop is traded internationally, anyway. The vast majority of wheat is consumed in-country.”

On preparing for coming “Katrinas” in agriculture…

“Neither as a nation, nor as a globe, have we matured in our governance to the extent that we can see the agricultural Katrinas and mobilize resources in a rational manner.

“Frankly, the United States’ situation is embarrassing and showing a lack of leadership. Last year, the United States attempted to withdraw all core support from all 15 international research centers studying crops.

“To spend billions of dollars in a war on terror and to ignore Mother Nature’s war on us — which is perpetual and forever — isn’t wise. We’re not going to defeat this rust, we’ll only manage it. And it’s only one of many emergent diseases we’re facing.

“Agricultural research must be accountable — I’m in complete agreement. But research is essential. We don’t question that we need road maintenance, teachers in school or a strong military. But agriculture research in the public sector?

“We aren’t talking about billions of dollars. Why Congress has to nitpick over a few million dollars that the U.S. scientific community, growers and millers believe is essential is (frustrating). We need to get our priorities straight.”

e-mail: [email protected]

About the Author(s)

David Bennett

Associate Editor, Delta Farm Press

David Bennett, associate editor for Delta Farm Press, is an Arkansan. He worked with a daily newspaper before joining Farm Press in 1994. Bennett writes about legislative and crop related issues in the Mid-South states.

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