Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1993
Publication Date: N/A
Interpretive Summary: Annual, national surveys of wheat and oat stem rust fungi to monitor changes in virulence are conducted at the Cereal Rust Lab. When a race with a new virulence gene or combination of virulence genes is detected, it is saved and used in selecting new cultivars with resistance to the new race as well as to previously identified races. For wheat stem rust, which also attacks barley, race Pgt-QCCJ was the most common race in 1992, comprising 50% of all isolates. Eighty percent of the isolates of QCCJ were from cultivated barley and 90% of all isolates from cultivated barley were race QCCJ. If only collections made from wheat were considered, the most common races were TPMK, QFCS and QCCJ, comprising 53, 21 and 16% of the isolates, respectively. Race NA-27 was again the predominant oat stem rust race comprising 90% of the population. In 1992, no major shift in races occurred and no new virulences were detected.
Technical Abstract: Wheat stem rust overwintered in southern and east central Texas, southern Louisiana, and southeastern Alabama. Yield losses to stem rust of wheat were traces; but a 1% yield loss in barley occurred in North Dakota. Race Pgt-QCCJ was the most common race making up 50% of the 450 isolates from 170 collections. If only the 89 collections from wheat were considered, the most common races were Pgt-TPMK, QFCS, and QCCJ, comprising 53, 21, and 16% of the isolates, respectively. Eighty percent of the isolates of QCCJ were from cultivated barley and 90% of all isolates from cultivated barley were race QCCJ. No virulence was found to wheat lines with "single" genes Sr13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 37, Gt, or Wld-1. Oat stem rust overwintered in southern Texas and southern Louisiana. Yield losses in 1992 were negligible. Race NA-27, virulent to Pg-1, -2, -3, -4, and -8, was again the predominant race in the United States, comprising 90% of the 279 isolates from 96 collections. NA-16, NA-5, and NA-23 were the other races isolated, comprising 7, 2, and 1% of the population, respectively. No virulence to Pg-9, -13, -16, or -a was found in the 1992 oat stem rust population.