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Researchers Launch 'Rust-Tracker' to Monitor Deadly Wheat Fungus

24 September 2012

The world's top wheat experts have reported a breakthrough in their ability to track Ug99 and related strains of a deadly and rapidly mutating wheat pathogen called stem rust that threatens wheat fields from East Africa to South Asia. With data submitted by farmers and scientists from fields and laboratories, the creators of the "Rust-Tracker" say they now can monitor an unprecedented 42 million hectares of wheat in 27 developing countries in the path of a windborne disease so virulent it could quickly turn a healthy field of wheat into a black mass of twisted stems and dried-up grains.

"Wheat rusts are global travellers with no respect for political boundaries, and it is highly likely that some of the virulent new strains related to Ug99 will eventually be carried across the Middle East and Central Asia and into the breadbaskets of Pakistan, China and India," said Dave Hodson, developer of Rust-Tracker and a scientist with the International Maize and Wheat Improvement Center (CIMMYT). "Effective control often depends on finding out what is happening in distant regions, and the Rust-Tracker can help scientists assess the status of stem rust and other rust diseases, not only in their own countries, but also in neighboring countries."

At the start of a four-day symposium organized in Beijing by the Borlaug Global Rust Initiative (BGRI), 1-4 September, scientists reported significant progress with developing and introducing 20 new varieties of rust-resistant wheat over the last few years. Seed for the new varieties is being deployed and multiplied in eight frontline nations to produce enough seed for farmers to plant to prevent massive crop loss in case of an epidemic. But the experts in Beijing warned that wheat fields in a significant number of countries remain largely unprotected from the dangerous pathogen.

"The research being presented at this meeting takes us significantly closer to our goal of protecting the global wheat crop from rust diseases," said Ronnie Coffman, principal investigator and director of the Durable Rust Resistance in Wheat Project and vice chair of BGRI. "But the vast wheat-growing region that stretches across North Africa and Central Asia all the way to the gateway to China—the world's largest wheat-growing nation—is still vulnerable."

Tracking the rusts

An estimated 85 percent of wheat now in production, including most wheat grown in the Americas, Asia and Africa, is susceptible to Ug99 and its variants. For now, however, only the original mutation, Ug99, has been found outside of Africa—in Yemen and Iran. Stem rust can cause farmers to lose their entire crop, but a second rust disease is already causing severe losses worldwide. Like stem rust, yellow rust (also known as stripe rust) has in recent years become more of an immediate threat, with the emergence of new, highly-aggressive strains that are able to knock out genetic resistance in many of the most popular varieties of wheat. Among the countries that have suffered devastating yellow rust epidemics are Azerbaijan, Ethiopia, Iraq, Morocco, Syria, Tajikistan and Uzbekistan, with yield losses as high as 40 percent.

"We need urgent concerted action to address yellow rust," said Mahmoud Solh, director general of the International Center for Agricultural Research in the Dry Areas (ICARDA). "It is a significant problem from the Middle East all the way to China. In any new varieties of wheat we develop, we need to build in durable resistance to both stem rust and yellow rust."

Using Rust-Tracker data, Hodson and his colleagues in Beijing are developing "risk maps" that can assist researchers in countries in the path of virulent strains of stem rust and yellow rust to assess the severity of the threat and prepare to resist it.

Taking the new wheat to the farmers

"The only manageable solution for farmers who cannot afford fungicides when rust hits is to replace their crop with new rust-resistant varieties," Coffman said. "And this is a challenge when the wheat looks healthy."

"Planting only five percent of a nation's wheat fields with seed from resistant varieties would allow replacement of susceptible varieties within a year, if Ug99 should appear," Coffman said.

Leading the efforts to accomplish that aim are Afghanistan, Bangladesh, Ethiopia, Egypt, India, Kenya, Nepal and Pakistan, which are choosing from among the more than 20 rust-resistant varieties developed by ICARDA and CIMMYT. All eight nations are expected to pass the 5 percent mark in the 2012-13 growing season. The new varieties are not only resistant to stem rust but to other rusts as well, Coffman said.

"It's frustrating," Coffman said. "We have the technology to prevent a tragedy that could destroy crops in one of the world's most important wheat-producing regions, an area that is already vulnerable to hunger and civil unrest. But the funding is not in place to get enough rust-resistant wheat seed multiplied fast enough and into the hands of the people who need it."

Further Reading

You can view the full report by clicking here.

September 2012

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