The ability of known ericoid mycorrhizal fungi to form mycorrhizae with Gaultheria shallon

Formation of structures resembling ericoid mycorrhizas by the root endophytic fungus Heteroconium chaetospira within roots of Rhododendron obtusum var. kaempferi

A resynthesis study was conducted to clarify the relationship between the root endophyte, Heteroconium chaetospira and the ericaceous plant, Rhododendron obtusum var. kaempferi. The host plant roots were recovered 2 months after inoculation, and the infection process and colonization pattern of the fungus were observed under a microscope. The hyphae of H. chaetospira developed structures resembling ericoid mycorrhizas, such as hyphal coils within the host epidermal cells. These structures were morphologically the same as previously reported ericoid mycorrhizal structures. The frequencies of hyphal coils within the epidermal cells of host roots ranged from 13 to 20%. H. chaetospira did not promote or reduce host plant growth. This is the first reported study that H. chaetospira is able to form structures resembling mycorrhizas within the roots of ericaceous plants.

Fungal endophytes from the roots of alpine and boreal Ericaceae

Oidiodendron mains Barron, Scytalidiutn vaccinii Dalpé, Litten, & Sigler, and a variable white taxon (VWT) were isolated consistently from the roots of ericaceous plants collected in three different habitats. Restriction fragment length polymorphism data were used to (i) clarify the identification of strains of O. maius with character states intermediate between O. maius and Oidiodendron griseum Robak, (ii) identify the VWT as distinct from S. vaccinii in spite of cultural similarities, and (iii) reveal that S. vaccinii comprises two genotypes correlated with habitat. Corn meal agar was used to induce conidiogenesis in S. vaccinii, and one strain produced apothecia consistent with the description of Hymenoscyphus ericae (Read) Korf & Kernan, confirming the anamorph–teleomorph relationship of these two taxa. Oidiodendron maius and S. vaccinii, already accepted as mycobionts of the Ericaceae, are confirmed as ubiquitous in natural habitats of Alberta and are often both isolated from the same root fragment. The isolation of Phialocephala fortinii Wang & Wilcox, a non-mycorrhizal endophyte of diverse plant families, from two of the sites but not from the acidic wetland indicates that its distribution depends on edaphic factors. Its vigorous growth on the initial isolation plates adversely affected the recovery of the other three taxa. Key words: ericoid mycorrhiza, Ericaceae, RFLP, Oidiodendron, Scytalidium, Hymenoscyphus, Phialocephala.