Virulence of Puccinia coronata in Relation to Available Genes for Resistance in Oats. L. J. Michel, Agricultural Research Technician, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, Iowa State University, Ames 50011. M. D. Simons, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, Iowa State University, Ames 50011. Plant Dis. 67:197-200. Accepted for publication 9 July 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-197.

Isolates of Puccinia coronata collected in the United States during 1976–1980 were assayed for virulence on 32 oat (Avena sativa) cultivars and lines having different genes for resistance. Most of the isolates that had been collected on oats were virulent on cultivars Trispernia, Bondvic, and Ukraine. Average percentage of isolates virulent on the others ranged from 0.1 to 46%. Virulence among the isolates showed no tendency to increase on two components of Iowa multiline cultivars IA X421 and IA X434 but did increase significantly on another, IA X475. Of three southern cultivars of oats, virulence increased markedly on TAM 0-312, moderately on TAM 0-301, and did not increase on Coker 234. Virulence of isolates from buckthorn (Rhamnus cathartica) generally paralleled that of isolates from oats. The number of virulence combinations represented by the isolates from oats varied from 36 in 1978 to 86 in 1976. Coker 234 and FL 723A2 were shown to probably carry the same gene for resistance to the crown rust pathogen.