The world's leading wheat experts from Australia, Asia, Africa, Europe and the Americas—invited to Mexico by Nobel Prize Winner Norman Borlaug—report significant progress in developing new varieties of wheat capable of resisting a virulent form of an old plant disease that threatens wheat production worldwide.
But research released at the Borlaug Global Rust Initiative 2009 Technical Workshop also confirmed that the dangerous and newly-emerged stem rust race known as Ug99 is now in Kenya, Uganda, Ethiopia, Sudan, Yemen and Iran, and is on the march toward South Asia. According to scientists at the four-day conference in Ciudad Obregón, longer distance movement to other regions cannot be excluded. They estimate that 90 percent of the varieties planted in farmers' fields around the world lack resistance to the pathogen. Named for its discovery in Uganda ten years ago, Ug99 is well established already in Kenya, where in some areas the reddish, wind-borne fungus has decimated 80 percent of the wheat in farmers' fields.
"We should keep a close eye on any movements into southern Africa as well, because there is historical evidence that high altitude winds and even hurricanes can transport plant pathogens from that region into the Americas and Australia, although these would be rare events," said David Hodson, a Geographic Information Systems (GIS) expert who is involved with the Global Cereal Rust Monitoring System and works with the Mexico-based International Maize and Wheat Improvement Center (in Spanish: Centro Internacional de Mejoramiento de Maíz y Trigo, or CIMMYT).
Every region of the world is represented at the meeting in Ciudad Obregón, which was organized by the Borlaug Global Rust Initiative, a group led by, among others, CIMMYT, the Syria-based International Center for Agricultural Research in the Dry Areas (ICARDA), Cornell University, the Food and Agriculture Organization of the United Nations (FAO), and the Indian Council of Agricultural Research (ICAR). Both CIMMYT and ICARDA are supported by the Consultative Group on International Agricultural Research (CGIAR).
New Varieties Showing Resistance to Ug99
In a new study released at the event, researchers from CIMMYT, ICARDA, the Kenya Agricultural Research Institute (KARI), and the Ethiopian Institute for Agricultural Research (EIAR) described a breakthrough in their efforts to develop new varieties of wheat that are not only resistant to Ug99, but also produce more grain than today's most popular varieties.
Ravi Singh, a CIMMYT wheat geneticist and pathologist and lead author of the study, said high-yielding, Ug99-resistant spring wheat varieties are rapidly emerging through an intensive international "shuttle breeding program." Breeding materials under development in CIMMYT's test fields in Ciudad Obregón and Toluca—and at ICARDA fields in Aleppo, Syria—are sent to Kenya and Ethiopia, where they are exposed to Ug99 in real world conditions. They are then sent back to Mexico or Syria for further refinement and then back to Kenya and Ethiopia for more exposure.
Through this approach, scientists—also shuttling between continents —have produced new types of high-yield wheat that contain what plant breeders call "multiple minor genes" that have resistance to Ug99. Though this strategy may not provide the same level of protection as that provided by one or two major genes, it is high enough to be effective, and the researchers believe that by forcing the fungus to overcome a larger array of genetic barriers, these new wheat varieties could provide long-term protection against future stem rust mutations.
There are numerous examples in the last century of stem rust mutating and "defeating" wheat plants that have contained single major resistance genes. One of the alarming hallmarks of Ug99 is that in Kenya it has mutated and overcome two additional major stem rust resistance genes called Sr24 and Sr36 that had been effective against the original form of Ug99.
"We believe that this approach of endowing a plant with many minor resistance genes in combination can provide resistance comparable to the best single major resistance gene, giving us the potential to end this dangerous arms race against wheat stem rust," Singh said, noting that many countries have contributed plant materials and expertise to the program.
Higher Yields Key in Promoting Resistant Varieties in at-Risk Regions
A significant achievement with the varieties produced in the project is that they provide superior yields. This is of major importance, as the battle against Ug99 appears to be shifting from a scientific challenge to a logistical one. Averting a crisis will require farmers to replace their existing varieties with resistant ones, even though they may not face an immediate threat from Ug99. But convincing the farmers to switch requires offering resistant varieties that also produce higher yields.
An update from the Global Cereal Rust Monitoring System shows that the mutated fungus could be headed for South Asia, where farmers, many of them poor subsistence growers, produce 19 percent of the world's wheat for a population of 1.4 billion people. The monitoring system also has implemented wind models showing that Ug99, which has moved out of eastern Africa to the Middle East, could soon travel to the Caucasus, Central Asia, or Afghanistan.
'Massive Effort" Needed to Combat Old Foe, Says Borlaug
Borlaug, whose call to action inspired the creation of the stem rust initiative, said that new findings regarding the expected trajectory of Ug99—and its wily ability to mutate quickly—reinforces the need for ongoing research and for supporting a massive effort to scale up production and distribution of resistant varieties in vulnerable nations.
"Our scientists are making incredibly rapid progress, but we should have no illusions: a global food crisis is still a distinct possibility if governments and international institutions fail to support this rescue mission," said Borlaug, who warned that, even in today's environment of dwindling resources, governments cannot afford to jeopardize a crop that provides 20 percent of the world's food calories.
Stem rust has plagued wheat farmers for thousands of years, but for the last 50 years it has been largely forgotten thanks to resistant varieties developed by a group of scientists lead by Borlaug. Their work, undertaken just a few miles from the site of the Obregón conference, is credited with launching a Green Revolution that saved billions from starvation and earned Borlaug a Nobel Peace Prize.
But in 1998, the stem rust variant discovered in Uganda showed itself able to overcome the resistance that had been established by Borlaug's team and refined over the years by a growing cadre of wheat breeders at national and international research centers. These experts watched with growing alarm as Ug99 quickly moved to Kenya, where it has undergone mutations and proven capable of cutting wheat yields by 20 to 80 percent, with isolated incidents of 100 percent destruction.
Producing and Introducing Resistant Varieties in Nations at Risk
The response on all fronts has been swift and is producing results far faster than anyone had expected. For example, researchers in Iran noted they have begun producing seed of the new varieties for testing in more extensive field trials. And scientists from India reported the results of an intensive campaign underway in different regions to convince farmers that they will need to switch to Ug99-resistant wheat before the disease arrives in the country.
Other efforts are underway to spur testing and seed production in Egypt, Bangladesh, Nepal, Ethiopia, and Afghanistan as part of the Famine Fund Wheat Rust Project funded by the US Agency for International Development (USAID).
GPS Tracking Units to Monitor Ug99 Migration; Warming Trends May Affect Path
Hodson said the monitoring project, which emerged from the BGRI partnership and will soon be under the auspices of FAO, recently distributed GPS tracking units and surveillance protocols to teams in 29 countries. The goal is to expand and accelerate the flow of real-time surveillance data to an online monitoring system that keeps track of Ug99 and provides timely information to decision-makers.
Scientists at the conference also considered new evidence that global warming could send stem rust into parts of the world where it has never been seen before. For example, Ug99 already has been found in a part of Iran where no wheat stem rust of any type had ever been documented. However, it is not clear whether its spread to that particular region is connected to climate change.
A team of researchers from the Southern Cone region of South America, where there are approximately 9 million hectares of wheat under cultivation, said there is intense interest in both the spread of Ug99 and the effort to develop resistant varieties. They noted that studies completed last year show that most of the wheat in the region is susceptible to Ug99.
Global Collaboration on Stem Rust Benefiting Science, Public
Many people involved in the conference said that the unprecedented effort to combat Ug99 has resulted in a new level of international scientific collaboration that could provide a range of benefits for global food production.
"What you see in Obregón is that we have put together a very powerful team for fighting Ug99, but its value extends well beyond this threat," said Ronnie Coffman, Director of the Durable Rust Resistance in Wheat project at Cornell. "Farmers also need more productive varieties to feed a growing population and they will need varieties that can survive any new stresses induced by climate change."
Thomas Lumpkin, Director General of CIMMYT, noted that the lack of investment over the last decades in wheat breeding programs and facilities has put the world in a weak position to combat newly emerging dangers such as Ug99. "It's a classic case in which few are aware of these deficiencies until the capabilities and innovations are needed," Lumpkin said. "The BGRI, through its coordinated efforts so evident in this meeting, is pulling us back from the brink of a Ug99 disaster. But the funding base for R&D is still too small to tackle problems such as emerging new disease strains and the increasing temperatures and water scarcity that are resulting from climate change in major wheat-producing areas."
Materials provided by Borlaug Global Rust Initiative. Note: Content may be edited for style and length.
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