The causal agent of wheat stem rust, produced large epidemics in North America and other parts of the world in the early 1950s. These epidemics were controlled by the deployment of stem rust resistance genes that have provided adequate resistance for the last several decades. Unfortunately, these genes are no longer effective against a new race of stem rust, Ug99, which was identified in Uganda in 1999.
The identification and mapping of new resistance genes effective against Ug99 is a high priority. Crop scientists have now mapped and characterized the stem rust resistance gene Sr35. This gene is effective against Ug99 and its derivatives, providing a useful tool to fight this new stem rust epidemic.
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