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Scientists Breed New Wheat to Resist Disease


International teams of plant scientists are stepping up their efforts to breed hardier types of wheat, a global food staple used to make bread, cereals and pasta. They're hoping the new wheat varieties will better resist the fungal diseases that are attacking wheat crops all over the world and threatening widespread food shortages.

Stem rust and other fungal crop diseases have been ravaging wheat crops in Kenya and Uganda for nearly a decade and are now threatening to infect millions of hectares of wheat and barley crops in other countries in Africa, across the Middle East and Asia.

Jorge Dubcovsky, an expert on wheat at the University of California at Davis, says it's vital that the world's wheat crops be protected from these aggressive fungal epidemics because wheat is so important to human nutrition:

"We cannot afford to keep losing 10 or 20 percent of our crops to pathogens. And 20 percent of their calories everyday is coming from wheat. So, either you produce 620 pounds (281 kilograms) in wheat ever year, or a lot of people will go hungry," he said.

Chemical fungicides offer some protection from rust diseases but they are costly and pose threats to the environment. The most profitable and environmentally friendly strategy for farmers, Dubcovsky believes, is to grow genetically resistant wheat varieties.

Dubcovsky is co-author of a paper published this week in the journal Science reporting the discovery of a novel resistance gene in wild wheat in Israel. When bred into commercial varieties, the gene gives bread and pasta grains protection against a destructive fungal disease called stripe rust.

Dubcovsky says the stripe rust is so aggressive that even with the modified gene, the wheat plant is only partially protected from the withering effects of the fungus.

"But it will be a lot slower, the infected areas will be smaller and at the end of the day if you have some infections, your varieties will be able to produce more," he said.

In a second study published in Science, an international group of researchers at the International Maize and Wheat Improvement Center, or CIMMYT in Mexico City, along with Australian and Swiss scientists, have concluded that a wheat gene called Lr34 that can give the plant long-term resistance to leaf rust, stripe rust, and powdery mildew.

They say they would first like to use it extensively to impart disease resistance to wheat bread crops, and then try to protect crops that are used to make pasta. Co-author Ravi Singh, one of the world's leading plant scientists, is also involved in a project to stop the spread of perhaps the most aggressive of the wheat diseases, stem rust, which can destroy crops in a matter of weeks. Singh says the Lr34 gene was probably involved in efforts 30 years ago to breed stem-rust resistant wheat.

"So, we have to still work on how it can also enhance the level of resistance to stem rust in the new wheat varieties," he said. "There are obviously other resistance genes, but we don't know at the genetic level what they do. CIMMYT is heavily engaged with many other institutions now in developing and testing wheat materials which are resistant."

Singh says he's hopeful the new rust-resistant wheat varieties will be available in at least eight affected countries, stretching from Africa to Asia, within the next two to three years.

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