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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #366606
Research Project: Cereal Rust: Pathogen Biology and Host Resistance

Location: Cereal Disease Lab

Title: First report of TTRTF race of wheat stem rust, Puccinia graminis f. sp. tritici, in Ethiopia

Author
item TSEGAAB, TESFAYE - Ethiopian Institute Of Agricultural Research
item ALEMAYEHU, CHALA - Hawassa University
item SHIKUR, ELFINESH - Hawassa University
item HODSON, DAVID - International Maize & Wheat Improvement Center (CIMMYT)
item Szabo, Les

Submitted to: Plant Disease Notes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2019
Publication Date: 10/28/2019
Citation: Tsegaab, T., Alemayehu, C., Shikur, E., Hodson, D.H., Szabo, L.J. 2019. First report of TTRTF race of wheat stem rust, Puccinia graminis f. sp. tritici, in Ethiopia. Plant Disease Notes. 104(1):293-293. https://doi.org/10.1094/PDIS-07-19-1390-PDN.
DOI: https://doi.org/10.1094/PDIS-07-19-1390-PDN

Interpretive Summary: Stem rust caused by Puccinia graminis f. sp. tritici is an important disease of bread and durum wheat in Ethiopia. The frequent emergence of new virulent races of wheat stem rust pathogen remains a major constraint to wheat production. Wheat stem rust surveys are carried out annually during both the main (late August through October) and off-seasons (June and July) in Ethiopia. During the annual 2017 main season survey, a total of 60 stem rust samples were collected from farmer's field in the major wheat growing areas of Oromia and Amhara Regions. Forty-eight single pustule isolates were derived from these samples and test on wheat stem rust differential lines to determine race types. Ten isolates collected from different regions were determined to be race TTRTF. Isolates belonging to this race were derived from stem rust samples from commercial wheat cultivars Digelu, Danda'a, Pavon 76, and Israel, as well as, Triticale. DNA genotyping was used to confirm the race phenotype data. Severe epidemics of wheat stem rust on durum wheat in Italy in 2016 and 2017 were caused by this new race of the wheat stem rust pathogen and has been detected in Egypt. These results show that this new virulent race of the wheat rust pathogen with complex virulence is spreading rapidly and has now become established in Ethiopia. Further spread is considered likely and close monitoring is required.

Technical Abstract: Stem rust caused by Puccinia graminis f. sp. tritici is an important disease of bread (Triticum aestivum L.) and durum (T. turgidum spp. durum) wheat in Ethiopia. The frequent emergence of new P. graminis f. sp. tritici virulent races remains a major constraint to wheat production. Wheat stem rust surveys are carried out annually during both the main (late August through October) and off-seasons (June and July) in Ethiopia. During the annual 2017 main season survey, a total of 60 stem rust samples were collected from farmer's field in the major wheat growing areas of Oromia and Amhara Regions. Forty-eight single pustule isolates were derived from these samples at Ambo Plant Protection Research Center (Ethiopia) and multiplied on susceptible wheat cultivar McNair 701. Physiological race analysis was performed using the 20 North American stem rust differential lines following the standard protocol by Jin et al. (2008). Race analysis was repeated up to seven times until the race was confirmed. Ten isolates collected from different zones were determined to be race TTRTF (Supplementary Table S1). Isolates belonging to this race were derived from stem rust samples from commercial wheat cultivars Digelu, Danda'a, Pavon 76, and Israel, as well as Triticale. Urediniospores of the 48 isolates were sent to the Cereal Disease Laboratory (CDL) St. Paul, Minnesota for genotyping. DNA was extracted from spores using the OmniPrep kit as described by Olivera et al. (2015) and genotyped using 17 selected single nucleotide polymorphism markers. All P. graminis f. sp. tritici isolates that were race typed as TTRTF, were genotyped as MLG.04 (clade III-B) and were identical to reference isolates for P. graminis f. sp. tritici race TTRTF. Virulence tests revealed that the race is virulent to 17 stem rust resistance genes (Sr5, Sr21, Sr9e, Sr7b, Sr11, Sr6, Sr8a, Sr9g, Sr36, Sr9b, Sr17, Sr9a, Sr9d, Sr10, SrTmp, Sr38, SrMcN) and avirulent to three stem rust resistance genes (Sr30, Sr24, Sr31). Severe epidemics of wheat stem rust on durum wheat in Italy in 2016 and 2017 were caused by race P. graminis f. sp. tritici TTRTF (Patpour et al., 2018). The same race has been also reported in Egypt from samples collected in 2016 (Samar and Szabo, 2018). However, this is the first confirmation of P. graminis f. sp. tritici race TTRTF in Ethiopia. These results indicate P. graminis f. sp. tritici TTRTF with complex virulence is spreading rapidly and has now established in Ethiopia. Further spread is considered likely and close monitoring is required.