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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVEMENT OF HARD RED SPRING AND DURUM WHEAT FOR DISEASE RESISTANCE AND QUALITY USING GENETICS AND GENOMICS Title: Evaluation and Characterization of Seedling Resistances to Stem Rust Ug99 Races in Wheat-Alien Species Derivatives

Authors
item Xu, Steven
item Jin, Yue
item Klindworth, Daryl
item Wang, Richard
item Cai, X - NORTH DAKOTA STATE UNIV.

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2009
Publication Date: November 1, 2009
Citation: Xu, S.S., Jin, Y., Klindworth, D.L., Wang, R., Cai, X. 2009. Evaluation and Characterization of Seedling Resistances to Stem Rust Ug99 Races in Wheat-Alien Species Derivatives. Crop Science. 49:2167–2175.

Interpretive Summary: Stem rust, a devastating disease of wheat, has been effectively controlled worldwide for the past 50 years by deployment of stem rust resistance (Sr) genes in wheat cultivars. However, a new stem rust race, known as Ug99, emerged in eastern Africa, is a cause of concerns because this race overcomes most of the stem rust resistance genes currently deployed in wheat cultivars worldwide. To identify new sources of stem rust resistance genes that are effective against Ug99, we evaluated and characterized the seedling resistance to Ug99 of 65 wheat lines derived from the crosses of bread wheat or durum wheat with eight wild relative species, including two goatgrass species (Aegilops speltoides and Ae. caudata) and six perennial wheatgrass species (Thinopyrum intermedium, Th. ponticum, Th. elongatum, Th. junceum, Th. bessarabicum, and Elymus rectisetus). The result showed that 34 wheat-alien species derivatives had resistance to Ug99. The comparisons of wheat-alien species derivatives and their parental lines for reactions to different races suggested that several lines carry novel genes for stem rust resistance. The results from this study suggested that the wheat-alien species derivatives are an important germplasm base for sources of stem rust resistance. The resistance lines identified in this study provide useful materials for introducing novel stem rust resistance genes into wheat breeding.

Technical Abstract: Stem rust, a devastating disease (caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & Henn.) of wheat (Triticum aestivium L.), has been effectively controlled worldwide for the past 50 years by deployment of stem rust resistance (Sr) genes in wheat cultivars. However, a new stem rust race, TTKSK (known as Ug99 or TTKS) that emerged in eastern Africa, is a cause of concerns because this race has a broad virulence combinations against currently deployed Sr genes. To identify new sources of Sr genes that are effective against Ug99, we evaluated and characterized the seedling resistance to TTKSK of 65 wheat lines derived from the crosses of common or durum wheat with Thinopyrum junceum, Th. intermedium, Th. bessarabicum, Th. elongatum, Th. ponticum, Elymus rectisetus, Aegilops caudata, and Ae. speltoides. For stem rust evaluation, we first tested all lines for reactions to races TTTT and TTKSK. Those lines initially showing resistance to TTKSK were then re-tested with eight races, including three races in the TTKS lineage (TTKSK, TTKST, and TTTSK), and five North American races (QFCS, QTHJ, RCRS, RKQQ and TPMK). The result showed that 34 wheat-alien species derivatives had resistance to TTKSK. The comparisons of wheat-alien species derivatives and their parental lines for reactions to different races suggested that several lines, including seven wheat-Th. intermedium amphiploids, one wheat-Th. ponticum amphiploid, six durum-Ae. speltoides amphiploids, one wheat-Th. junceum disomic addition line, two wheat-Ae. caudata disomic addition lines, and a wheat-Th. bessarabicum 7J disomic addition line, might carry novel genes for stem rust resistance. These lines provide useful materials for introducing novel stem rust resistance genes into wheat breeding.

Last Modified: 10/23/2014