Mycorrhizas of the ericaceae: Diversity and systematics of the mycobionts

This research comprises two approaches to the study of the ericoid mycorrhizal association in natural environments in Alberta, Canada. The first is ecological in focus; the objective was to isolate and identify the mycorrhizal endophytes of plant species in the Ericaceae native to Alberta. The second focus is on the evolution and systematics of the mycobionts; the objective was to examine the taxonomic and phylogenetic relationships among the taxa recovered.; Fungal endophytes were isolated from surface-sterilized roots of 19 plant species in the Ericaceae collected from three distinct habitats: alpine heathland, stable sand dune and acidic peatland. Fungi were identified using morphological characters, molecular analysis with restriction endonucleases was used to clarify the delimitation of sterile taxa and the affiliation of strains with atypical morphology. A total of 269 plant collections was processed and all had the typical morphology of ericoid mycorrhizal complexes in their roots.; Four fungal taxa were considered common root endophytes: Scytalidium vaccinii; Oidiodendron maius; an unidentified sterile fungus, named Variable White Taxon (VWT) and characterized with molecular markers; and Phialocephala fortinii. RFLP markers revealed two genotypes within S. vaccinii. The genetic difference was significant at the sub-specific level and correlated with habitat; Type I was from the alpine heathland and sand dune while Type II was from the bog. One Type II strain of S. vaccinii produced apothecia of Hymenoscyphus ericae (Leotiales) in culture, confirming a previous suggestion that the two species are conspecific.; Using nuclear ribosomal DNA sequences (internal transcribed spacer region), species delimitation in the asexual genus Oidiodendron was clarified and its putative phylogenetic placement in the Myxotrichaceae (Onygenales) was examined. Three monophyletic groups, each one a pair of species, were resolved within Oidiodendron. A low level of sequence divergence within each pair suggested conspecificity. Conidiophore, length and pigment production were too variable for species identification and several historically important ericoid Oidiodendron strains were re-identified as O. maius. All species were resolved as part of a monophyletic group within the Myxotrichaceae. Parsimony analysis of small subunit rDNA sequences confirmed the hypothesis that the four ascomycetous fungi isolated from roots of the Ericaceae share a common ancestor with inoperculate discomycetes. Thus the inferred phylogenetic placement for the Myxotrichaceae is within the Leotiales and the Onygenales is revealed as polyphyletic.