Seven new species associated with Australian terrestrial orchids.

is one of the main fungal genera that form mutualistic associations with species of orchids (Orchidaceae). Here, seven new species associated with various Australian orchid genera are described. These species were originally characterized by multilocus DNA sequence species delimitation analyses (three mtDNA and four nuclear genes) and confirmed as distinct with addition of further isolates and reanalysis of nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and nuc 28S rDNA (28S). Culture morphology and microscopic features are presented for each species, three of which are binucleate and four multinucleate. For the ITS region, the seven species have within-species sequence divergence between 1.07% and 4.31%, and all but one of the species pairs is separated by interspecific divergence of at least 4.35%. The newly described species, , and , are shown to be separate species from on the basis of comparison against a sequence from the type. Isolates originally identified by Warcup as "" from orchids are revised and shown to belong to three of the species newly described here. Some non- isolates identified by Warcup as . "" are also shown to be non-conspecific with the type of . On the basis of ITS sequences, 346 isolates from 26 other studies, previously identified under provisional designations, are accommodated under the novel species. The species of described here associate with the Australian orchid genera , and . Most of the novel species occur widely across Australia, often with widely distributed hosts, but one species, , associates with narrowly distributed orchid species.