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Title: Virulence races of Puccinia striiformis f. sp. in 2006 and 2007 and development of wheat stripe rust and distributions, dynamics, and evolutionary relationships of races from 2000 to 2007 in the United States

Author
item Chen, Xianming
item PENMAN, LAURA - WASHINGTON STATE UNIV
item WAN, ANMIN - WASHINGTON STATE UNIV
item CHENG, PENG - WASHINGTON STATE UNIV

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2010
Publication Date: 8/10/2010
Citation: Chen, X., Penman, L., Wan, A., Cheng, P. 2010. Virulence races of Puccinia striiformis f. sp. in 2006 and 2007 and development of wheat stripe rust and distributions, dynamics, and evolutionary relationships of races from 2000 to 2007 in the United States. Canadian Journal of Plant Pathology. 32:315-323.

Interpretive Summary: Stripe rust historically has been most frequently destructive on wheat in the western United States and has become more frequent in the central and southeastern states since 2000. Races of PST have been determined every year from rust infected leaf samples of wheat and grasses collected in the U.S. on a set of 20 differential wheat genotypes. A total of 115 races were detected, of which 78 were first detected from 2000 to 2007. The predominant races were the group with virulences on resistance genes Yr8 and Yr9 and some other genes, which were first detected in 2000. The group continued to evolve into races with various combinations of virulences on differential genotypes with various resistance genes. From 2000 to 2003, the predominant races were PST-78 and PST-80, which are virulent on differential wheat genotypes Lemhi, Heines VII, Lee, Fielder, Express, AVS/6*Yr8, AVS/6*Yr9, Clement, and Compair. Race PST-80 is also virulent on Produra. In 2003 to 2006, the predominant race was PST-100, with the same virulences as PST-80 plus virulences on Yamhill and Stephens. Starting in 2006, races with the virulences of PST-100 plus virulence on resistance gene Yr1 became predominant in California and races with the virulence of PST-100 plus virulence on Yr10 became predominant in the Pacific Northwest. During the eight-year period, races with more virulences became more predominant, indicating that races with more virulences have advantages for increasing in the pathogen population over those with fewer virulences because they are able to infect more wheat cultivars. The information on virulences of races and their distribution in various epidemiological regions, frequncy changes, and their evolutionary relationships should be useful for guiding breeding programs to use effective types and genes of resistance to control the devastating disease.

Technical Abstract: Strip rust, caused by Puccinia striiformis f. sp. tritici (PST), has been historically most frequently destructive on wheat (Triticum aestivum) in the western United States and has become more frequent in the central and southeastern states since 2000. Races of PST have been determined every year from rust infected leaf samples of wheat and grasses collected in the U.S. on a set of 20 differential wheat genotypes. A total of 115 races were detected, of which 78 were first detected, from 2000 to 2007. The predominant races were the group that was virulent on Lemhi (Yr21), Heines VII (Yr2 and YrHVII), Lee (Yr7, Yr22, and Yr23), Fielder (Yr6 and Yr20), Express (YrExp1 and YrExp2), AVS/6*Yr8 (Yr8), AVS/6*Yr9 (Yr9), Clement (Yr9 and YrCle), and Compair (Yr8 and Yr19), which were first detected in 2000. The group continued to evolve into races with various combinations of virulences on differential genotypes Chinese 166 (Yr1), Moro (Yr10 and YrMor), Paha (YrPa1, YrPa2, and YrPa3), Druchamp (Yr3a, YrDru, and YrDru2), Produra (YrPr1 and YrPr2), Yamhill (Yr2, Yr4a, and YrYam), Tyee (YrTye), Tres (YrTr1 and YrTr2), and/or Hyak (Yr17 and YrTye). From 2000 to 2003, the predominant races were PST-78 and PST-80, which are virulent on wheat genotypes Lemhi, Heines VII, Lee, Fielder, Express, AVS/6*Yr8, AVS/6*Yr9, Clement and Compair. Race PST-80 is also virulent on Produra. In 2003 to 2006, the predominant race was PST-100, with the same virulences as PST-80 plus virulences on Yamhill and Stephens. Starting in 2006, races with the virulences of PST-100 plus virulence on Yr1 became predominant in California and races with the virulence of PST-100 plus virulence on Yr10 became predominant in the Pacific Northwest. During the eight-year period, races with more virulences became more predominant, indicating that races with more virulences have advantages for increasing in the pathogen population over those with fewer virulences because they are able to infect more wheat cultivars.