Field Resistance of Oats to Puccinia graminis f. sp. avenae Measured via Yield and Seed Weight Reduction. A. H. Epstein, Professor of Plant Pathology, ARS, U.S. Department of Agriculture, Department of Plant Pathology, Iowa State University, Ames 50011. M. D. Simons, K. J. Frey, and P. G. Rothman. Research Plant Pathologist, ARS, U.S. Department of Agriculture, Department of Plant Pathology, C. F. Curtiss Distinguished Professor in Agriculture, Department of Agronomy, Iowa State University, Ames 50011; and Research Plant Pathologist, ARS, U.S. Department of Agriculture, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 72:154-156. Accepted for publication 29 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0154.

To determine whether currently grown, seedling-susceptible oat (Avena sativa) lines varied in field resistance to stem rust (Puccinia graminis f. sp. avenae), we tested 150 lines in the field in 1982 and 240 in 1983 and 1985. Data were expressed as resistance indexes obtained by dividing yields and 200-seed weights of diseased plots by corresponding values from rustfree plots. Infection and resulting damage were severe. Ranges of resistance indexes for yield were 0.11–0.76, 0.23–0.84, and 0.32–0.99 in 1982, 1983, and 1985, respectively. Corresponding ranges of resistance indexes for seed weight were 0.23–0.66, 0.34–0.68, and 0.40–0.79. Variation among lines for indexes was significant (P = 0.01) in all 3 yr.

Keyword(s): disease tolerance, slow rusting.