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United States Department of Agriculture

Agricultural Research Service

Title: Resistance in U.S. wheat to recent Eastern African isolates of Puccinia graminis f. sp. tritici with virulence to resistance gene Sr31

Authors
item JIN, YUE
item Singh, Ravi - CIMMYT, MEXICO

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 2005
Publication Date: November 8, 2005
Citation: Jin, Y., Singh, R. 2005. Resistance in U.S. wheat to recent Eastern African isolates of Puccinia graminis f. sp. tritici with virulence to resistance gene Sr31. Plant Disease. 90:476-480.

Interpretive Summary: The stem rust of wheat historically was one of the most destructive plant diseases. A stem rust resistance gene, Sr31, has been used as the main component for stem rust resistance in many wheat cultivars worldwide. Isolates of the stem rust pathogen, Puccinia graminis f. sp. tritici with virulence on Sr31, was identified from Uganda in 1999. Similar virulence was observed in Kenya in 2003 and 2004. Studies were undertaken to identify resistance to the African race in U.S. wheat. Four hundred fifty cultivars and advanced breeding lines of various wheat classes from the United States were tested against two stem rust isolates. Resistance to this new stem rust race was detected in all classes of wheat with the following frequencies: 16% of hard red spring wheat, 48% of the hard red winter wheat, and 27% of soft winter wheat. Genes conferring resistance in the U.S. spring wheat are unknown. Resistance in spring wheat cultivars was likely derived from Thatcher, and resistance in cultivar Ivan was likely due to Sr24. Resistance in the hard red winter wheat was primarily due to Sr24, and resistance in soft winter wheat was primarily due to Sr36. The identification of new sources of resistance in the adapted germplasm may present an opportunity to improve wheat with resistance to this new virulence and to lessen the vulnerability of wheat to the new stem rust race.

Technical Abstract: The stem rust resistance gene Sr31 derived from rye has been used as an important source of stem rust resistance in many wheat cultivars worldwide. Isolates of Puccinia graminis f. sp. tritici with virulence on Sr31 were identified from Uganda in 1999. Stem rust susceptibility in wheat lines with Sr31 was observed in Kenya in 2003 and 2004. An isolate collected from Uganda in 1999 and an isolate collected from Kenya in 2004, identified to be race TTKS, were used in the rust evaluations. Cultivars and advanced breeding lines of various wheat classes from the United States (450 in total) were tested against these two stem rust isolates. Resistance to race TTKS was detected in all classes of wheat with following frequencies: 16% of hard red spring wheat, 48% of the hard red winter wheat, and 27% of soft winter wheat. The genes that conferred resistance in the U.S. spring wheat have not been conclusively identified. Resistance in spring wheat cultivars Chris, Guard, Wheaton, Norm, Stoa, and Keene was likely derived from the cultivar Thatcher, and resistance in cultivar Ivan was likely due to Sr24. Resistance in the hard red winter wheat was postulated to be primarily due to Sr24, and resistance in soft winter wheat was postulated to be primarily due to Sr36. The 1AL.1RS translocation present in many U.S. winter wheat cultivars and breeding lines appears to carry an effective resistance gene different from Sr31. The identification of resistance to race TTKS in the adapted germplasm presents an opportunity to improve stem rust resistance in wheat and to lessen the vulnerability of wheat to the new stem rust race.

Last Modified: 9/29/2014
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