Disease Note.

First Report of La France Disease of Agaricus bisporus in Spain. I. Zabalgogeazcoa, Laboratorio de Virologia Vegetal, CIT-INIA, Ctra. de La Coruna km 7, 28040 Madrid.. V. Torres, C. de Blas and F. Ponz, Laboratorio de Virologia Vegetal, CIT-INIA, Ctra. de La Coruna km 7, 28040 Madrid, and V. Rubio, Centro Nacional de Biotecnologia, CSIC-Universidad Au((5noma de Madrid, 28049 Madrid, Spain. Plant Dis. 79:424. Accepted for publication 17 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0424A.

Mushroom samples from farms where bare spots in the cover soil and drumstick-shaped sporophores had been observed, were analyzed for the presence of double-stranded RNA (dsRNA). The nine dsRNA segments associated with La France disease (I) were observed by agarosc electrophoresis in symptomatic mushroom samples collected in several areas of the Spanish regions of Navarra, La Rioja, and Castilla-La Mancha. La France disease-associated dsRNAs were also detected in mushrooms not showing symptoms, but coming from farms where productivity had declined. The nine dsRNA segments were not present in apparently healthy mushrooms picked at farms where production was good. No viral disease symptoms were reported during the summer months, when the production in La Rioja was switched to Agaricus bitorauis. This mushroom grows belter than A. bisporus in warm weather conditions and does not show symptoms of La France disease. To our knowledge, this is the first report of the occurrence of La France disease of mushrooms in Spain.