Races of Puccinia graminis in the United States during 1994

Wheat stem rust overwintered in southern Louisiana and Texas in the winter of 1993-94. Wheat stem rust caused negligible yield losses in wheat in the U.S. Race Pgt-TPMK was the most common race on wheat, making up 39% from 51 collections, while Pgt-QCCJ was most common from barley, making up 90% from 38 collections. Four collections from Hordeum jubatum yielded six isolates of race TMPK, four isolates of race QCCJ, and one each of races RKQQ and RTQQ. No virulence was found to wheat lines with genes Sr13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, or Wld-1. Oat stem rust was first found in mid-April in southern Texas and Louisiana. Yield losses due to oat stem rust in 1994 were negligible. Race NA-27, virulent to Pg-1, -2, -3, -4, and -8, was again the predominant race in the United States, constituting 87% of the 119 isolates from 41 collections. NA-5 and NA-16 were the two other races identified from the U.S., constituting 3 and 10% of the isolates, respectively. Only race NA-29 was found in 50 collections from central Mexico.