Submitted to: Oat Newsletter
Publication Type: Other
Publication Acceptance Date: June 15, 2000
Publication Date: N/A
Technical Abstract: There was less oat stem rust in the Southeast in 1999 than 1998, when stem rust was unusually prevalent. Losses to stem rust in the U.S. were light in 1999 with only Texas reporting measurable yield loss at 1%. Race NA27, the predominant race of oat stem rust in the U.S. for many years, made up 96% of the collections in 1999. A new stem rust race with virulence to Pg-1,-2,-3,-4, -8,-9, and -13, which was first found in 1998, was found again in South Dakota and Minnesota in 1999. Oat crown rust was widespread in the South in 1999 with yield losses ranging from 0.5% in Louisiana to 3% in Texas and North Carolina. Cool spring weather delayed the development of crown rust in the Midwest in 1999. Losses to crown rust in Minnesota, South Dakota, and Wisconsin at 2%, 3%. and 1% were similar to those in 1998, but losses in North Dakota were greater in 1999 at 5%. Frequencies of virulence to oat crown rust resistance genes in 1998 changed little from those in recent years. No virulence was found to Pc68 and only one isolate with virulence to Pc45 was found in 1999. Virulence to Pc58 remained low in Texas and the Midwest, but occurred at 21% in the Southeast. Oat cultivar TAM-O-393 remained resistance to nearly all isolates of crown rust from fields, but 20% of the aecial isolates from buckthorn in Minnesota in 1999 were virulent on TAM-O-393.