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Septoria nodorum on Barley and Relationships Among Isolates from Several Hosts. Barry M. Cunfer, Department of Plant Pathology, University of Georgia, Georgia Station, Experiment 30212; John Youmans, Department of Plant Pathology, University of Georgia, Georgia Station, Experiment 30212. Phytopathology 73:911-914. Accepted for publication 20 December 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-911.

The causal agent of a leaf spot and glume blotch of barley and little barley (Hordeum pusillum) in Georgia was identified as Septoria nodorum. Symptoms are described. Conidial morphology of isolates from both hosts was identical to that of isolates from wheat and triticale. Isolates from barley and wheat were highly virulent to their original host but weakly virulent to the opposite crop in reciprocal inoculations. Isolates from H. pusillum were pathogenic to all four plant species. Isolates from triticale were similar to those from wheat by all criteria tested. S. nodorum was isolated from seeds of all four hosts. Isolates from wheat, triticale, and H. pusillum were fluorescent under near-ultraviolet light on unrefined media and when grown on autoclaved wheat and barley seeds placed on oxgall agar whereas most isolates from barley were nonfluorescent. Fluorescent isolates from barley were identical to isolates from wheat in cultural characters on six media and in pathogenicity. Isolates from wheat and barley with differing characters are considered to be biotypes of S. nodorum. Colony characters must be noted carefully during assays from barley seed on oxgall agar since most isolates are nonfluorescent.