Brown blotch caused by Pseudomonas tolaasii on cultivated Pleurotus eryngii in Spain.
In 2006, symptoms of brown blotch were observed on cultivated Pleurotus eryngii (king oyster mushroom) in Castilla-La Mancha (Spain). Subsequently, between January and May 2008, brown blotch affected 39.75% of the blocks, resulting in a considerable loss of production. Symptoms observed were principally characterized by a yellowish brown-to-orangish colour, first of the cap and then of the stalk. Some samples also showed a slightly concave cap. From samples collected from different king oyster mushroom farms, a fluorescent gram-negative bacterium was recovered on King's B medium and identified as Pseudomonas tolaasii by the LOPAT scheme and other tests. This was further confirmed by molecular investigations and pathogenicity tests. This is thought to be the first report of Pseudomonas tolaasii causing brown blotch on Pleurotus eryngii in Spain.