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Poster: Epidemiology: Population Biology Genetics


Stripe rust epidemics of wheat and barley and races of Puccinia striiformis identified in the United States in 2015
X. CHEN (1), A. Wan (2) (1) USDA-ARS, U.S.A.; (2) Department of Plant Pathologist, Washington State University, U.S.A.

In 2015, stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), occurred throughout the United States and caused severe yield losses in the Great Plains. Stripe rust of barley, caused by P. striiformis f. sp. hordei (Psh), occurred in California, Montana, Oregon, Utah, and Washington. For monitoring virulence changes of the pathogens, stripe rust samples collected from 21 states were tested on 18 wheat and 12 barley differentials to identify Pst and Psh races, respectively. From 32 Psh isolates, three previously existing races were detected, of which PSH-48 (virulent only on Topper among the 12 barley differentials) and PSH-33 (virulent on differentials Topper and Abed Binder 12) were the major races with frequencies of 53% and 54%, respectively, similar to 2014. From 310 Pst isolates, 32 races were detected including 5 new races (PSTv-140, PSTv-141, PSTv-142, PSTv-143, and PSTv-144). The top five frequent Pst races were PSTv-37 (36%), PSTv-52 (33%), PSTv-18 (5%), PSTv-53 (4%), and PSTv-48 (3%). PSTv-37 and PSTv-52 were detected in every epidemiological regions, while PSTv-18, PSTv-53, and PSTv-48 were detected only in the western U.S. High virulence frequencies (>50%) were detected for Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44, and YrExp2; moderate (10-50%) for Yr1, YrTr1, and YrTye; low (<10%) for Yr10, Yr24, Yr32, and YrSP; and none for Yr5 and Yr15. The information is useful for breeding for resistance and management of stripe rust.