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Reactions of Smooth Bromegrass Accessions to Brown Leaf Spot Caused by Pyrenophora bromi. K. E. Zeiders, Research Plant Pathologist, USDA-ARS, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. R. T. Sherwood, Research Plant Pathologist, and C. C. Berg, Research Agronomist, USDA-ARS, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. Plant Dis. 70:324-326. Accepted for publication 25 September 1985. 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, 1986. DOI: 10.1094/PD-70-324.

Plants of 93 accessions from 13 foreign countries and the United States and five commercial cultivars of smooth bromegrass (Bromus inermis) were screened for resistance to brown leaf spot by inoculations with Drechslera bromi, the conidial state of Pyrenophora bromi. On a scale of 15, mean disease severity ratings for brown leaf spot ranged from 3.2 to 4.1 (overall mean 3.7), or from moderately to highly susceptible. No smooth bromegrass entry was highly resistant to P. bromi; however, 174 resistant plants (rating of 2 or lower) were selected from among 70 entries after the first inoculation. No resistant plants were selected from 28 of the entries. After a second inoculation, the overall mean disease rating of selected plants was 2.72 0.92, whereas the mean of 21 selected susceptible plants was 4.36 0.59. Mean disease ratings of five commercial cultivars were similar (range 3.53.7). The susceptibility of smooth bromegrass germ plasm to infection by P. bromi did not differ much in this broad-based population.

Keyword(s): disease resistance, Helminthosporium bromi.