First report of Puccinia graminis f.sp. tritici race TTKTT in Ethiopia.
Stem rust, caused by Puccinia graminis f.sp. tritici (Pgt), is one of the most important diseases affecting wheat production in Ethiopia, with crop losses of up to 100% during epidemic years. In recent years, different virulent races of Pgt have been identified in the major wheat production areas of the country. Ethiopia is considered as a hot spot for the development and spread of new Pgt races. During the 2018 main cropping season (June to December), wheat rust surveys were undertaken in major wheat growing regions of Ethiopia, and stem rust was recorded in 284 (39%) of the 727 wheat fields surveyed. A total of 333 stem rust samples were analyzed for race identity using 20 North American wheat lines to differentiate Pgt races following the standard protocol described by Jin et al. (2008). The analysis identified seven races, namely, TTTTF, TKTTF, TTKTT, TKKTF, TKPTF, TTRTF, and TTKTF. Of these, TTKTT was detected for the first time in Ethiopia. Race TTKTT was virulent to wheat differential lines containing Sr5, Sr6, Sr7b, Sr8a, Sr9a, Sr9b, Sr9d, Sr9e, Sr9g, Sr10, Sr11, Sr17, Sr21, Sr24, Sr30, Sr31, Sr38, SrTmp, and SrMcN and avirulent on lines with Sr36. This race was identified independently by AmARC and RCRRC in replicated tests from 18 isolates collected in Guji (southern Ethiopia), West Arsi (southeastern Ethiopia), Hararge (eastern Ethiopia), and East Wellega (western Ethiopia) zones of Oromia region and two isolates from East Gojam and South Wollo zones of Amhara region. Race TTKTT was identified from samples collected from commercial wheat cultivars Hulluka, Senate, Shorima, Ogolcho, Hidase and Danda'a.