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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETICS, POPULATION BIOLOGY, AND HOST-PARASITE INTERACTIONS OF CEREAL RUST FUNGI AND THEIR DISEASES

Location: Cereal Disease Laboratory

Title: Sources of resistance to stem rust race Ug99 in spring wheat germplasm

Authors
item Rouse, Matthew
item Wanyera, Ruth -
item Njau, P -
item Jin, Yue

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2011
Publication Date: June 7, 2011
Citation: Rouse, M.N., Wanyera, R., Njau, P., Jin, Y. 2011. Sources of resistance to stem rust race Ug99 in spring wheat germplasm. Plant Disease. 95:762-766.

Interpretive Summary: Wheat stem rust is an important disease of wheat. Race TTKSK (Ug99) and its variants from Africa possess virulence to many important stem rust resistance used in wheat breeding. In order to protect wheat from this rapidly spreading and adapting pathogen, multiple resistance genes are needed, preferably from improved germplasm. Preliminary screening of over 700 spring wheat older breeding lines and cultivars in Njoro, Kenya identified 88 accessions with field resistance to Ug99. The accessions were also screened with a bulk of North American isolates of P. graminis f. sp. tritici (Pgt) in the field in St. Paul, Minnesota. In order to further characterize the resistance in these accessions, we obtained seedling phenotypes for ten races of Pgt, including two races from the race TTKSK complex. This phenotyping led to the identification of accessions with either adult-plant or all-stage resistance to race TTKSK and often North American races of Pgt as well. Resistance to Ug99 identified in these accessions could be usd for improving wheat for stem rust resistance.

Technical Abstract: Wheat stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks & E. Henn.) race TTKSK (Ug99) with virulence to the majority of the world’s wheat (Triticum aestivum L.) varieties has spread from Uganda throughout eastern and southern Africa, Yemen, and Iran. The identification and spread of variants of race TTKSK with virulence to additional stem rust resistance genes has warned breeders and pathologists of the danger of deploying major resistance genes alone. In order to protect wheat from this rapidly spreading and adapting pathogen, multiple resistance genes are needed, preferably from improved germplasm. Preliminary screening of over 700 spring wheat older breeding lines and cultivars identified 88 accessions with field resistance to Ug99. We included these resistant accessions in the stem rust screening nursery in Njoro, Kenya for two additional seasons. The accessions were also screened with a bulk of North American isolates of P. graminis f. sp. tritici (Pgt) in the field in St. Paul, Minnesota. In order to further characterize the resistance in these accessions, we obtained seedling phenotypes for ten races of Pgt, including two races from the race TTKSK complex. This phenotyping led to the identification of accessions with either adult-plant or all-stage resistance to race TTKSK and often North American races of Pgt as well. Resistance to Ug99 identified in these accessions can be introgressed into current breeding germplasm.

Last Modified: 8/27/2014
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