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Molecular Plant Pathology

Hybridization Analysis of the Single-Stranded RNA Bacilliform Virus Associated with La France Disease of Agaricus bisporus. C. Peter Romaine, Associate professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; B. Schlagnhaufer, research assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 81:1336-1340. Accepted for publication 28 June 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-1336.

We investigated the relationship between the 19- × 50-nm single-stranded RNA (ssRNA) mushroom bacilliform virus (MBV) and the double-stranded RNAs (dsRNAs) associated with La France disease of Agaricus bisporus. Agarose gel electrophoresis under formaldehyde-denaturing conditions revealed that the MBV genome was composed of a single RNA molecule of 4.4 kb. In northern analyses, a 1.4-kb cloned complementary DNA (cDNA) to MBV RNA hybridized to the full-length genomic RNA in purified virus preparations and total RNA fractions from diseased mushrooms. A minor 1.8-kb RNA, presumably a subgenomic component, also was detected in diseased tissues. No cross hybridization occurred between this MBV cDNA clone and total RNA of healthy mushrooms. When we used either the cDNA or a combination of the nine La France disease-related dsRNAs (0.8 to 3.8 kb) as a hybridization probe, no sequence homology existed between MBV RNA and the dsRNAs found in diseased as well as healthy tissues. Our findings are consistent with the hypothesis that a viral complex involving an ssRNA virus and an unrelated dsRNA virus(es) plays a role in the etiology of La France disease.