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Identification of Resistance to Cephalosporium Stripe in Winter Wheat. J. B. Morton, Department of Plant Pathology, Montana State University, Bozeman 59717, Current address of senior author: Cargill PAG Research, P. O. Box 146, Lubbock, TX 79408; D. E. Mathre, Department of Plant Pathology, Montana State University, Bozeman 59717. Phytopathology 70:812-817. Accepted for publication 1 March 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-812.

Seven winter wheat cultivars were examined for resistance to Cephalosporium gramineum. Two types of resistance were observed: exclusion of the pathogen and restriction of spread of the pathogen following successful colonization of the host. The former was expressed as a reduction in the percentage of diseased plants. The latter was expressed as a reduction in the percentage of diseased tillers per infected plant and also as a reduction in the rate and severity of disease development. Both types of resistance were expressed independently. PI 278212 exhibited a low infection percentage, but was rapidly and completely invaded after successful ingress. Crest LRC 40 demonstrated a high percentage of diseased plants, but restricted infection between tillers, and had a moderate rate of systemic invasion. Each type of resistance may be identified and evaluated separately if seeding rates permit recognition of individual plants. Maximum resistance would be attained if both types of resistance were incorporated into a single genotype. Infection occurred only in soils undergoing frost-heaving, confirming that broken roots are essential for ingress of the fungus into the host. Differential responses between cultivars to pathogen exclusion could not be attributed to gross changes in either propagule levels in the soil or root mass. Cumulative effects of microhabitat interactions between the soil-root interface or differential responses to wound-healing are suggested as possible explanations for dissimilarities between cultivars.