Molecular diversity of ericoid mycorrhizal fungi

Using restriction fragment length polymorphism (RFLP) patterns from two rib osomal internal transcribed spacers (ITS) and DNA sequences from ITS2, we c haracterized ericoid mycorrhizal fungal isolates from culture collections.W ith a synoptic key to RFLP patterns, we divided 34 mycorrhizal or root-asso ciated isolates into 16 groups. RFLP patterns were identical when fungal sp ecific primers were used to amplify DNA from pure fungal cultures and in vi tro mycorrhizae. Sequence analysis clustered 23 of 24 mycorrhizal isolates into two larger groups: the Oidiodendron group and the Hymenoscyphus group. The Oidiodendron group included genetically uniform, conidiating fungi. Th e Hymenoscyphus group encompassed more diversity and included other discomy cetes (Leotiales) as well as sterile, unidentifiable mycorrhizal isolates f rom four RFLP groups. Results from our field site on Vancouver Island, Brit ish Columbia, Canada, suggest that several ericoid mycorrhizal fungi can co exist in a single root of Gaultheria shallon Pursh and that our molecular d ata base is not yet complete. From sixty 3-mm root sections, we cultured fo ur genetically different fungi that formed mycorrhizae in resynthesis exper iments and sequence analysis showed that one of these differed from all pre viously known ericoid mycorrhizal fungi.