Diverse Helotiales associated with the roots of three species of Arctic Ericaceae provide no evidence for host specificity

Ericoid mycorrhizal fungi differ in their abilities to use nitrogen sources and may be integral to maintaining fungal and plant diversity in ecosystems in which Ericaceae occur. In this study, we tested whether the fungal communities differ among three species of co-occurring Ericaceae. Fungi colonizing Cassiope tetragona, Empetrum nigrum and Vaccinium vitisidaea roots in the Arctic tundra were characterized via culture-dependent and culture-independent techniques. The cultured fungi were tested for their ability to colonize Vaccinium uliginosum in laboratory-based assays. The pure-cultured Helotiales were grouped into eight clades and dominated by the Phialocephala-Acephala complex. Representatives of these clades, plus an unknown basidiomycete with affinity to the genus Irpex (Polyporales), colonized V. uliginosum intracellularly. The Helotiales detected by direct PCR, cloning and sequencing were assigned to 14 clades and dominated by members of the Rhizoscyphus ericae complex. Ordination analyses indicated that culture-dependent and culture-independent assays provided distinct views of root fungal communities, but no evidence for host specificity. These data suggest that ericaceous roots host diverse fungal communities dominated by the Helotiales. However, these fungal communities are unlikely to be controlled by fungal host preferences. The mechanisms maintaining high diversity in root-symbiotic communities remain to be elucidated.