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Etiology

Double-Stranded RNAs Associated with La France Disease of the Commercial Mushroom. Mark P. Wach, Former graduate research assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address: Monterey Mushrooms, 777 Maher Ct., Watsonville, CA 95077; Alagacone Sriskantha(2), and C. Peter Romaine(3). (2)Former graduate research assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address: Australia Biotechnology Ltd. Pty., Sydney, Australia; (3)Associate professor of plant pathology, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 77:1321-1325. Accepted for publication 25 February 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1321.

Double-stranded RNA (dsRNA) analysis was used to clarify the purported viral etiology of La France disease of the commercial mushroom, Agaricus bisporus. Healthy and diseased sporophores were collected at 65 sites on commercial farms, and dsRNA patterns were compared after phenol extraction, cellulose column chromatography, gel electrophoresis, and ethidium bromide staining. DsRNA was detected in 19 of 22 diseased sporophore isolates and none of 43 healthy sporophore isolates. The presence of a characteristic dsRNA pattern correlated positively with La France disease symptoms. The dsRNA pattern consisted of 2.50, 2.05, 1.90, 1.70, 1.10, 0.89, 0.58, and 0.53 × 10⁶ molecular weight (MW) segments. Variation in the disease-specific dsRNA pattern between sporophore isolates involved deletions of various dsRNA segments and additions of 4.5, 0.34, 0.33, 0.28, and 0.27 × 10⁶ MW dsRNAs. Symptoms associated with the dsRNAs manifested as a reduced yield and, at some sites, as sporophores with elongated stems and small caps. The disclosed association of a characteristic dsRNA pattern with diseased sporophores provides strong circumstantial evidence for the etiologic role of specific virus(es) in La France disease.