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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #321735
Title: Emergence of virulence to SrTmp in the Ug99 race group of wheat stem rust, Puccinia graminis f.sp. tritici in Africa

Author
item PATPOUR, MEHRAN - Aarhus University
item HOVMOLLER, MOGENS - Aarhus University
item JUSTESEN, A - Aarhus University
item NEWCOMB, MARIA - University Of Arizona
item OLIVERA, PABLO - University Of Minnesota
item Jin, Yue
item Szabo, Les
item HODSON, DAVID - International Maize & Wheat Improvement Center (CIMMYT)
item SHAHIN, ATEF - Kafrelsheikh University
item WANYERA, RUTH - Kenya Agricultural Research Institute
item HABARUREMA, I - Rwanda Agriculture Board (RAB)
item WOBIBI, S - National Agricultural Research Organization - Uganda

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2015
Publication Date: 7/1/2016
Citation: Patpour, M., Hovmoller, M., Justesen, A.F., Newcomb, M., Olivera, P., Jin, Y., Szabo, L.J., Hodson, D., Shahin, A., Wanyera, R., Habarurema, I., Wobibi, S. 2016. Emergence of virulence to SrTmp in the Ug99 race group of wheat stem rust, Puccinia graminis f.sp. tritici in Africa. Plant Disease. 106:729-736.

Interpretive Summary: The Ug99 race (TTKSK) of wheat stem rust was first detected in Uganda in 1998, and since then seven additional variants have been reported. In this study, 84 stem rust samples from the 2014 surveys of wheat fields in east Africa were sent to the Global Rust Reference Center (GRRC, Denmark) for race analysis. Puccinia graminis f. sp. tritici (Pgt) isolates were recovered on cv. Morocco, and resulting urediniospores of 53 single-pustule isolates were inoculated onto 20 the North American stem rust differential lines set using standard procedures. The pathotyping was repeated in two or three independent experiments using single-pustule isolates. Twelve of the derived isolates were also typed at the USDA-ARS Cereal Disease Laboratory (USA) for an independent confirmation. A new race, TTKTK, similar to TTKSK except for additional virulence to SrTmp was found in Kenya, Uganda, Rwanda, and Egypt. A second new race, TTKTT with virulence to SrTmp and Sr24, was found in Kenya. The emergence identification of SrTmp virulence in the Ug99 race group in several countries in one year emphasizes the need for relevance of coordinated international surveillance efforts and the utilization of diverse sources of resistance to control stem rust in wheat. Further studies are in progress to determine the detailed relationship of the newly emerged races and other Pgt isolates identified in the Ug99 lineage group. The information obtained through this study is important for agricultural scientists and producers in rust surveillance and in breeding for stem rust resistance.

Technical Abstract: The Ug99 race (TTKSK) of wheat stem rust was first detected in Uganda in 1998, and since then seven additional variants have been reported, i.e., TTKSF, TTKST, TTTSK, TTKSP, PTKSK, PTKST, and TTKSF+. In this study, 84 stem rust samples from the 2014 surveys of wheat fields in east Africa (Kenya, 9; Uganda, 28; Rwanda, 41; and Egypt, 6) were sent to the Global Rust Reference Center (GRRC, Denmark) for race analysis. Puccinia graminis f. sp. tritici (Pgt) isolates samples were recovered on cv. Morocco, and resulting urediniospores of 53 single-pustule isolates were inoculated onto 20 the North American stem rust differential lines set using standard procedures. The pathotyping was repeated in two or three independent experiments using single-pustule isolates. Twelve of the derived isolates were also typed at the USDA-ARS Cereal Disease Laboratory (USA) for an independent confirmation. Among the Kenyan samples, four collected from Njoro (Central Rift, cvs. Robin and Kwale) and two from Ntulumeti and Olgilai (South Rift, cv. Robin), were typed as TTKTK. Race TTKTK was is similar to TTKSK except for additional virulence to SrTmp. An additional single-pustule isolate derived from one of the samples from Njoro showed a high infection type on LcSr24Ag and CnsSrTmp, testers for Sr24 and SrTmp, respectively, and was typed as TTKTT. These isolates were also tested on Siouxland (PI 483469, Sr24+Sr31), Sisson (PI 617053, Sr31+Sr36), and Triumph 64 (CI 13679, donor of SrTmp) to confirm their virulence/avirulence combinations to Sr24, Sr31, Sr36, and SrTmp. Race TTKTK was also detected at two locations in Uganda (Rubaya and Muko in Kabale region) and at five locations in Rwanda (Kinigi, Rwerere, Rufungo research stations, Gatebe and Kamenyo). Three isolates derived from stem rust samples collected on cv. PBW343 (carrying Sr31) in Sakha in the Nile Delta region in Egypt were also typed as TTKTK. The emergence identification of SrTmp virulence in the Ug99 race group in several countries in one year emphasizes the need for relevance of coordinated international surveillance efforts and the utilization of diverse sources of resistance to control stem rust in wheat. Further studies are in progress to determine the detailed relationship of the newly emerged races and other Pgt isolates identified in the Ug99 lineage group.