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Lecanicillium fungicola causes dry bubble disease and is an important problem in the cultivation of Agaricus bisporus. Little is known about the defense of mushrooms against pathogens in general and L. fungicola in particular. In plants and animals, a first attack by a pathogen often induces a systemic response that results in an acquired resistance to subsequent attacks by the same pathogen. The development of functionally similar responses in these two eukaryotic kingdoms indicates that they are important to all multi-cellular organisms. We investigated if such responses also occur in the interaction between the white button mushroom and L. fungicola. A first infection of mushrooms of the commercial A. bisporus strain Sylvan A15 by L. fungicola did not induce systemic resistance against a subsequent infection. Similar results were obtained with the A. bisporus strain MES01497, which was demonstrated to be more resistant to dry bubble disease. Apparently, fruiting bodies of A. bisporus do not express induced resistance against L. fungicola.

Dry bubble disease is a major problem in the commercial cultivation of the white button mushroom Agaricus bisporus and is caused by the ascomycete Lecanicillium fungicola. In the casing layer, germination of L. fungicola spores is inhibited by the microflora, a phenomenon known as fungistasis. Fungistasis is annulled when the casing is colonized by A. bisporus hyphae. We demonstrated that addition of A. bisporus-associated sugars, similarly annulled the casing fungistasis. However, casing fungistasis does not seem to be based on competition for resources as L. fungicola spores germinate regardless of nutrient availability. Pseudomonas bacteria are a dominant group of bacteria in the casing and have previously been implied to be essential for the development of fungistasis in soils. Antibiotics produced by model strain Pseudomonas fluorescens CHA0 inhibited L. fungicola spore germination. Addition of glucose desensitized spores of L. fungicola, which resulted in germination in the presence of antibiotics. We conclude that antibiotics produced by the microflora most likely cause fungistasis.

Dry bubble disease is a major problem in the commercial cultivation of the white button mushroom Agaricus bisporus and is caused by the ascomycete Lecanicillium fungicola. In the casing layer, germination of L. fungicola spores is inhibited by the microflora, a phenomenon known as fungistasis. Fungistasis is annulled when the casing is colonized by A. bisporus hyphae. We demonstrated that addition of A. bisporus-associated sugars, similarly annulled the casing fungistasis. However, casing fungistasis does not seem to be based on competition for resources as L. fungicola spores germinate regardless of nutrient availability. Pseudomonas bacteria are a dominant group of bacteria in the casing and have previously been implied to be essential for the development of fungistasis in soils. Antibiotics produced by model strain Pseudomonas fluorescens CHA0 inhibited L. fungicola spore germination. Addition of glucose desensitized spores of L. fungicola, which resulted in germination in the presence of antibiotics. We conclude that antibiotics produced by the microflora most likely cause fungistasis.