Abstract
A new Rhizoctonia-like fungus associated with ectomycorrhizal tips of evergreen oak inoculated with Tuber melanosporum is described. Tulasnella tubericola sp. nov. is characterized by its particular habitat, apparently not associated with the roots of any orchid species, its fast-growing rate in plate culture, the creamy-white to pale orange tones of the colonies, the production of both typical globose monilioid cells together with terminal, finger-like monilioid projections and the absence of true sclerotia. In addition, phylogenetic analyses based on the sequences of the internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA) showed that the different isolates that define the new species constitute an isolated, monophyletic lineage within the genus. The fungus is exclusively isolated from mycorrhizal roots of Quercus ilex subsp. ballota, being absent both in the culture substrate or in the natural soil employed in the mycorrhization processes. No sexual fruiting bodies have been observed or induced in the laboratory for this fungus.