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Disease Note

First Report of Soybean Naturally Infected with Leptosphaerulina briosiana.. A. P. Grybauskas, Department of Botany, University of Maryland, College Park 20742. Plant Dis. 70:1159. Accepted for publication 3 September 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1159e.

Leptosphaerulina briosiana (Poll.) Graham & Luttrell was identified as the causal agent of a leaf spot on soybean (Glycine max (L.) Merr. ‘Ware’) field-grown on the Wye Research and Education Center farm near Queenstown, Maryland, in 1982. An infected leaflet from lower canopy leaves bearing small necrotic lesions from which isolations were made has been deposited with the University of Maryland Herbarium (accession 45767). Ascocarps 102–147 μm in diameter (122 μm mean) and 96% muriform ascospores (3–4 × 0–2 septate) measuring 14.6–22.2 × 38.2–50.0 μm (16.6 × 44.1 μm mean), corresponding to L. briosiana (1), readily developed on V-8 juice agar. Koch’s postulates were completed in the greenhouse on soybean cultivars Ware and Miles. This is the first report of a field occurrence of this disease in the United States. The relative importance of this disease is still unknown, however, because subsequent surveys (1983–1985) failed to recover the pathogen from the field.