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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #334424
Title: Characterization of Puccinia graminis f.sp. tritici isolates derived from an unusual wheat stem rust outbreak in Germany in 2013

Author
item OLIVERA, OLIVERA - University Of Minnesota
item NEWCOMB, MARIA - University Of Minnesota
item FLATH, KERSTIN - Julius Kuhn Institute
item Szabo, Les
item Rouse, Matthew - Matt
item Gale, Sam
item Carter, Melissa
item Luster, Douglas - Doug
item Jin, Yue

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2017
Publication Date: 10/1/2017
Citation: Olivera, O., Newcomb, M., Flath, K., Szabo, L.J., Rouse, M.N., Gale, S.W., Carter, M.L., Luster, D.G., Jin, Y. 2017. Characterization of Puccinia graminis f.sp. tritici isolates derived from an unusual wheat stem rust outbreak in Germany in 2013. Plant Pathology. 66:1258-1266.

Interpretive Summary: Stem rust of wheat is an import disease impacting yield and quality. The disease had been absent in Western Europe for more than 40 years until recently. An unusual stem rust infestation occurred in German wheat fields in summer 2013. We analyzed 48 isolates of the stem rust pathogen Puccinia graminis f. sp. tritici (Pgt) derived from 16 stem rust samples. Six races were identified: TKTTF, TKKTF, TKPTF, TKKTP, PKPTF, and MMMTF. None of these races belongs to the TTKS (Ug99) race group. German isolates of race TKTTF are phenotypically different to the ones responsible for the stem rust epidemic in Ethiopia in 2013/14 season. Phylogenetic analysis showed that these isolates represented two distinct lineages (clade IV and clade V). Thirty-eight isolates clustered into clade IV, which previously was defined by Ethiopian isolates of race TKTTF. Race TKKTP is of special concern due to its combined virulence to resistance genes Sr24, SrTmp and Sr1RSAmigo that are important for resistance to Ug99 in North American germplasm. Evaluation of US and international winter wheat breeding germplasm revealed that a high portion (55%) of Ug99 (or TTKSK)-resistant breeding lines are susceptible to race TKKTP. This research confirmed the presence of important virulence in Germany. This information should be useful for breeders to select diverse and effective resistance genes in order to provide more durable stem rust resistance and reduce the use of fungicides.

Technical Abstract: An unusual stem rust infestation occurred in German wheat fields in summer 2013. We analyzed 48 isolates derived from 16 Puccinia graminis f. sp. tritici (Pgt) samples and six races were identified: TKTTF, TKKTF, TKPTF, TKKTP, PKPTF, and MMMTF. Infection type and genotypic data confirm that none of these races belongs to the TTKS (Ug99) race group. German isolates of race TKTTF are phenotypically different to the ones responsible for the stem rust epidemic in Ethiopia in 2013/14 season. Forty isolates were genotyped using a custom SNP array. Phylogenetic analysis showed that these 40 isolates represented two distinct lineages (clade IV and clade V). Thirty-eight isolates clustered into clade IV, which previously was defined by Ethiopian isolates of race TKTTF. Race TKKTP is of special concern due to its combined virulence to Sr24, SrTmp and Sr1RSAmigo. The vulnerability to race TKKTP in US and international winter wheat is confirmed as 55% of North American and international cultivars and breeding lines resistant to race TTKSK (Ug99) became susceptible to TKKTP. Races identified in Germany in 2013 confirmed the presence of virulence to important stem rust resistance genes that are effective against race TTKSK. This information should be useful for breeders to select diverse and effective resistance genes in order to provide more durable stem rust resistance and reduce the use of fungicides.