Leptodontidium quercuum: antagonism to Lentinula edodes in Quercus logs and conidiogenesis

Abstract

A dematiaceous hyphomycete, Leptodontidium quercuum, was found to be an extremely deleterious antagonistic fungus for log cultivation of Lentinula edodes, or Shiitake. In response to the approach of Lentinula edodes hyphae, the antagonist formed distinct, narrow, and shiny black zone lines in outer sapwood, cambium, and inner bark regions of Quercus bed logs. The zone line was a pseudosclerotic plate consisting of several layers of thick-walled, highly pigmented cells, and caused deadlock of the two fungi. Abundant slime material was exuded from Leptodontidium quercuum hyphae during the formation of pseudosclerotic plates. Neither bleaching nor decay occurred in the regions occupied by Leptodontidium quercuum where lumens of wood fibers, tracheids, vessels, and ray parenchyma were filled with its black sclerotic cells. Conidia of Leptodontidium quercuum formed on agar culture media after 2 to several months of incubation at 20 °C. Scanning electron microscopy revealed that development of conidia was either sympodial or phialidic. However, their occurrence in nature and function in dispersal and colonization remain unknown. Key words: Leptodontidium quercuum, Lentinula edodes, mushroom cultivation, Quercus bed logs, antagonism, conidiogenesis.