Mutant Wheat Rust Has Scientists Worried

Mutant Wheat Rust Has Scientists Worried

New Ug99 strains get past built-in genetic protections.

In a release issued ahead of a major conference in Russia this week, scientists from the Borlaug Global Rust Initiative announced the discovery of four new mutations of the Ug99 rust strain. What has wheat pathologists worried is that these mutants have overcome existing forms of genetic resistance.

Leading wheat experts from Australia, Asia, Africa, Europe and the Americas are in Russia for a global wheat event organized by the Borlaug Global Rust Initiative.

In a statement, Ravi Singh, senior scientist in plant genetics and pathology with the Mexico-based International Maize and What Improvement Center, notes: "With the new mutations we are seeing, countries cannot afford to wait until rust 'bites' them. The variant of Ug99 identified in Kenya, for example, went from first detection in trace amounts in one year to epidemic proportions the next year."

Most varieties planted in the world's wheat fields are susceptible to the original form of Ug99. Breeders will now work to make sure every new wheat variety released has resistance to the original form and the new races, Singh pointed out.

The reddish-brown, wind-borne fungus known as Ug99 has decimated up to 80 percent of Kenyan farmers' wheat during several cropping seasons, and scientists estimate that 90% of the wheat varieties around the world lack sufficient resistance to the original Ug99. Starting five years ago, in response to evidence of Ug99's virulence, researchers expanded breeding programs and collaborated with each other in a kind of "shuttle breeding diplomacy" to identify wheat varieties that could resist the new strain. But the new mutations - identified last year in South Africa - will make wheat crops more vulnerable as pathogens now will find new wind trajectories for migration.

First discovered in Uganda in 1999, the original Ug99 has also been found in Kenya, Ethiopia, Sudan, Yemen and Iran; a Global Cereal Rust Monitoring System, housed at the Food and Agriculture Organization of the United Nations (FAO), suggests it is on the march toward South Asia and beyond. Its trajectory and evolution are of particular concern to the major wheat-growing areas of Southern and Eastern Africa, the Central Asian Republics, the Caucasus, the Indian subcontinent, South America, Australia and North America.

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