An inherited "neoplasm" in fungus.

An abnormal growth form in the fungus Schizophyllum commune is described that interferes with the development of reproductive structures. The abnormality, which takes the form of relatively large, compact, hemispherical bodies, depends on a dominant Mendelian gene, mound, for its expression. When mound is expressed in a mycelium that has the potential to form fruiting bodies, the fruiting response is affected and the effect is variable within a replicate series: fruiting bodies may be normal or abnormal, abort at various stages, or not develop at all. Occasionally, fruit bodies are overgrown and are completely enveloped by the hemispherical bodies. When hyphae from hemispherical bodies are subcultured, a seemingly normal mycelium forms that eventually differentiates hemispherical structures, but the ability to form fruiting bodies in not expressed. Continuous mycelial subculture has shown this loss of fruiting expression to be a permanent transformation, which is demonstrated to be a characteristic of hemispherical bodies.