Monday, 16 June 2008

::> Potentially devastating wheat rust spreading

Jun 11, 2008 9:38 AM, By David Bennett
Farm Press Editorial Staff

Since the 1950s, resistance genes bred into wheat varieties have held truly devastating stem rust epidemics in check. However, a new race of the rust, Ug99, has overcome many of those resistance genes and is marching east through southern Asia.

Ug99 first appeared in Uganda wheat in 1999 and spread to Kenya and Ethiopia during the next few years.

“At that point, many international scientists said, ‘This is something we need to check because this new race can overcome many of the effective resistances,’” said David Marshall, research leader with the USDA-ARS in North Carolina last spring.

“And that included the resistances that are in the international germ plasm out of the International Maize and Wheat Improvement Center near Mexico City. That’s alarming and this rust has become a front-burner issue.”

The spread of Ug99 through east Africa “raised a red flag and the USDA, in cooperation with CIMMYT and other international breeding centers, set up a program to identify germ plasm worldwide, based on how it fares — resistant, intermediate, or susceptible — with the new rust race,” said Marshall.

That research, done in large part with the Global Rust Initiative (see, continues to move forward.

Unfortunately, so does Ug99. By last year, the rust had leapt from Africa into Yemen. Now confirmed in Iran, wind patterns suggest Ug99 could have also reached the northern Middle East, Afghanistan, India and Pakistan. Some 20 percent of the world’s wheat is grown in India and Pakistan.


Milus is disappointed that Congress doesn’t understand what’s at stake with the disease. “On top of everything, our government has cut USAID (United States Agency for International Development) funding for just this sort of work. For this fiscal year, 2008, the money that’s been providing base support for international research centers — not just for wheat, but all crops — has been cut to zero. Congress cut next year’s funding, as well.”

This is shortsighted in the extreme, insists Milus. “The disease can be erratic but under the right environmental conditions, there can be 100 percent loss in infected fields. It can be devastating.”

Both men laud the Bill and Melinda Gates Foundation, which pledged $26.7 million towards monitoring and combating the rust for the next three years.


“UG99 took out many of the core resistance genes we’ve relied on for decades. That has left us extremely vulnerable. There are a small number of genes still effective. Right now, the strategy is to, as quickly as possible, move those into adapted varieties and get them into farmers’ hands.”

The International Maize and Wheat Improvement Center (CIMMYT) is “working frantically” to do just that, says Milus. “They have a small number of experimental lines already on seed increase with genes they think will provide effective resistance. They’ll deploy those in India, Pakistan and parts of Africa. But it takes time. Just to increase seed stocks to cover a couple of countries takes two or three years.”

Predicting the rust’s movement is very tricky, says Peterson. There have been attempts to match up information on wind flow and the disease’s progress out of Africa.

“CIMMYT has done a tremendous job predicting movement based on wind flow. But one event can throw everything off. Last year, one major wind event essentially moved the rust from Yemen into Iran. “

Disturbingly, additional wind events have since been recorded that “could have already moved the disease into India and Pakistan. That isn’t a definite — and nothing has been found on the ground. But the model says it’s possibly there.”

For more on Ug99 see


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