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POSTERS: Genetics of resistance

Races of Puccinia graminisf. sp. tritici with virulence to stem rust resistance genes effective against Ug99
Yue Jin - USDA-ARS Cereal Disease Laboratory. Pablo Olivera Firpo- University of Minnesota

Wheat stem rust, caused by Puccinia graminisf. sp.tritici(Pgt), is a reemerging disease posing threat to wheat production worldwide, as exemplified by the occurrence and spread of Sr31-virulent races in the Ug99 race group. In an effort to mitigate the impact of Ug99, several resistance genes effective against races in the Ug99 group were identified and bred into commercial varieties. In the last six years, several stem rust outbreaks and local epidemics have occurred in East Africa, Europe and Central Asia. Surprisingly, all of these recent stem rust events were caused by Pgtraces not related to Ug99. Some of these races, such as TKTTF and TTRTF, have been found with a wide geographic distribution, as they have been identified in the Caucasus, Europe, and East Africa. Besides causing severe damage on bread and durum wheat crops and significant losses to wheat farmers, many of these Pgtraces have significant virulence combinations on genes that are effective against races in the Ug99 race group. Virulence to Srgenes alone or in combinations have been observed on Sr13a, Sr22, Sr32, Sr35, Sr37, Sr40, Sr45, Sr53, and Sr1RSAmigo. These results highlight the need for continued efforts in identifying new stem rust resistance genes that are effective not only against races in the Ug99 group, but also effective against these newly emerged races with broad virulence combinations.