Disease Note.

First Report of Wheat Soilborne Mosaic Virus in Oregon. M. L. Putnam, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. T. W. Carroll, Department of Plant Pathology, Montana State University, Bozeman 59717; and R. French, USDA-ARS, Department of Plant Pathology, University of Nebraska, Lincoln 68583. Plant Dis. 78:102. Accepted for publication 4 October 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0102E.

Striking yellow mosaic symptoms and stunting of winter wheat (Triticum aestivum L. 'Madsen') were observed in late March and early April in a field near Scappoose, Oregon. Approximately I ha within a 22-ha field was affected. Light microscopy revealed large, brown, vacuolate inclusions in epidermal cells of symptomatic wheat stained with calcomine-orange and Luxol brilliant green, characteristic of wheat soilborne mosaic virus (WSBMV) infection. WSBMV in leaf extracts was confirmed by immunosorbent electron microscopy, using a WSBMV-specific rabbit antiserum (E. M. Ball, University of Nebraska); rigid, rodlike particles 18 nm wide and of two length classes, 65-105 and 270-390 nm, were observed. A Nebraska isolate of WSBMV used as a control had particles about 17 nm wide and 89-102 and 218-359 nm long. Reverse transcriptase polymerase chain reaction (PCR) assays of these diseased wheat samples using primers specific to WSBMV RNA-2 (1) (5-ATGCTTAATGGCGTGAGTAA-3' and 5'-CTCGAACCTTCCCATTTCAA-3') amplified an approximately 380-bp product, as did WSBMV controls. The PCR products hybridized strongly with a full-length WSBMV RNA-2 cDNA clone. This is the first report of WSBMV occurring west of the central Great Plains of the United States and represents a significant expansion of the range of the virus