Winter Wheat Genotype Responses to Cephalosporium gramineum Inoculum Levels. J. M. Martin, Associate Professor of Agronomy, Department of Plant and Soil Science, Montana State University, Bozeman 59717. D. E. Mathre, Professor, and R. H. Johnston, Research Associate, Department of Plant Pathology, Montana State University, Bozeman 59717. Plant Dis. 70:421-423. Accepted for publication 19 November 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-421.

Environmental factors influence grain yield and reactions of winter wheat to the soilborne fungus Cephalosporium gramineum. As a result, resistance of winter wheat genotypes can vary from trial to trial. One reason may be that genotypes respond differently to varying inoculum levels. Six genotypes ranging in susceptibility to C. gramineum were tested for their responses to varying levels of inoculum. Lenore, Winridge, Marias, MT 7579, PI 094424, and PI 278212 were inoculated with five levels (0, 5, 10, 15, and 30 g/3 m of row) of oat kernel inoculum in a replicated trial at Bozeman, MT, in 1983 and 1984. The genotypes responded differentially to increasing levels of inoculum. PI 278212 and PI 094424 were least susceptible and Marias was most susceptible. Lenore showed less yield reduction than Winridge and MT 7579, despite infection levels equal to or greater than those in these two genotypes. Resistance was not overcome at the inoculum levels used in this study, suggesting that the high yield reduction in resistant lines in some years is influenced more by an unknown environmental component than by inoculum level.