Diversity of sterile root-associated fungi of two Mediterranean plants

The diversity of dark sterile mycelia (DSM) associated with the roots ofneighboring healthy ectomycorrhizal Pinus halepensis and endomycorrhizalRosmarinus officinalis plants in a Mediterranean ecosystem in Italy wasinvestigated to assess taxonomic affinities of these poorly known rootendophytes. More than 260 fungal isolates were obtained and ascribed todistinct morphotypes based on their macro- and microscopic features.Polymerase chain reaction-restriction fragment length polymorphism andsequence analyses of the internal transcribed spacers (ITS1-5.8S-ITS2) and18S rDNA regions were carried out for representatives of the morphotypesobtained from both hosts over an 11-yr period. Molecular evidence matchedmorphological group circumscription. Recognition of systematic affinitieswas possible with varying degrees of resolution for the differentmorphotypes. Morph 2 was closely related to Rhizopycnis vagum (withinDothideomycetidae), Morph 1 to Diaporthe Phomopsis (withinSordariomycetidae), whereas Morphs 3a, 3b, 3c and 3d could only be giventaxonomic placement at a higher level (Dothideomycetidae andChaetothyriomycetidae). This peculiar systematic spectrum suggests thatactual DSM diversity in nature is still largely underestimated.Morphophysiological convergence among morphotypes, and ecological traitspossibly involved in interactions with plant hosts are discussed.