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POSTERS: Genetics of resistance

Stripe rust epidemics of wheat and barley and races of Puccinia striiformis identified in the United States in 2018
Xianming Chen - USDA-ARS. Meinan Wang- Washington Sate University

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), occurred in more than 16 states and stripe rust of barley, caused by P. striiformis f. sp. hordei (Psh), occurred mainly in the western U.S. For monitoring virulence changes of the pathogens, stripe rust samples were tested on 18 wheat and 12 barley differentials to identify Pst and Psh races, respectively. Twelve Psh races were detected, including 11 previously existing and one new race, of which PSH-33 (virulent on barley differentials Topper and Abed Binder 12) and PSH-97 (virulent on Topper, Abed Binder 12, and Bancroft) were the predominant races with frequencies of 20.0% and 17.1%, respectively. Of 26 Pst races identified, 24 were previously existing and two new races, PSTv-378 virulent on Yr1, Yr6, and Yr8 and PSTv-379 virulent on Yr1, Yr6, Yr9, Yr27, YrSP, YrTr1, and Yr76. The five predominant races were PSTv-37 (41.4%), PSTv-52 (11.9%), PSTv-322 (6.6%), PSTv-39 (6.1%), and PSTv-201 (5.7%) with PSTv-37 detected in all sampled states, PSTv-52 in five eastern and western states, and PSTv-39, PSTv-201, and PSTv-322 almost restrictively in the western states. The frequencies of virulence to Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44, YrTr1, and YrExp2 were high (60.4-89.3%) while those to Yr1, Yr10, Yr24, Yr32, YrSP, and Yr76 were low (2.2-27.6%). No virulence was detected to either Yr5 or Yr15. The results are useful for breeding resistant cultivars and control of stripe rust.