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Scientists Discover Gene to Combat Devastating Wheat Rust

USDA scientists and their partners have found a molecular tool that will help control wheat stem rust, a fungal disease threatening much of the world’s wheat supply.

First reported in 1999 in Uganda, wheat stem rust–caused by the Ug99 pathogen–is a devastating disease in several countries in Africa and the Middle East where losses can be up to 70 percent. Many experts predict this specific strain could spread rapidly, causing a wheat shortage affecting food security worldwide. Ninety percent of the wheat grown worldwide is susceptible, so if no preventive action is taken, it could cause wheat shortages and affect food security.

Current wheat varieties do not have resistance to this specific strain of Ug99.  However, USDA Agricultural Research Service (ARS) scientists in the Cereal Disease Laboratory in St. Paul, Minn., searched the USDA germplasm collections for wheat and its wild relatives to discover the resistance gene Sr35 that is effective against Ug99. The gene was found in Triticum monococcum, a close relative of pasta and bread wheat. Now, scientists with the Triticeae-Coordinated Agriculture Project (T-CAP) and Kansas State University have copied this gene.

The study, authored by Eduard Akhunov at Kansas State University and Jorge Dubcovsky at the University of California-Davis, was published in today’s issue of the journal Science. As part of the study, co-author Matt Rouse, an ARS plant pathologist at St. Paul, screened wheat varieties for Ug99 resistance at the only U.S. laboratory authorized to handle the Ug99 plant pathogens.

This research, funded by USDA’s National Institute of Food and Agriculture (NIFA) and ARS, represents an important milestone in the fight against this potentially devastating disease. The Sr35 gene, when bred into commercial varieties, confers near-immunity against Ug99 and other related strains. The gene has already been deployed by ARS wheat geneticists into U.S. wheat varieties.

Wheat lines transformed with Sr35 are resistant to Ug99, suggesting that biotechnological approaches can be used to control this disease. This work also builds a platform for further understanding the molecular mechanisms involved in the interactions between the stem rust pathogen and wheat. This work shows promise for developing more durable strategies to control this devastating disease.

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