1 Pisolithus.- 2 Suillus.- 3 Laccaria.- 4 Hebeloma.- 5 Rhizopogon.- 6 Tuber.- 7 Scleroderma.- 8 Amanita.- 9 Paxillus.- 10 Cantharellus.- 11 Lactarius.- 12 Cenococcum.- 13 Hysterangium.- 14 Thelephora.- 15 Resupinate Ectomycorrhizal Fungal Genera.

Ectomycorrhizal fungi : key genera in profile

Aproximately 5,000–6,000 fungal species form ectomyorrhizae (ECM), the symbiotic organs with roots of predominantly trees. The contributing fungi are not evenly distributed over the system of fungi. Within Basidiomycota exclusively Hymenomycetes and within Ascomycota exclusively Ascomycetes contribute to the symbiosis. Hymenomycetes play a big part, Ascomycetes a minor role; Zygomycetes only form exceptionally ECM. Responsible for ascomycetous ECM are mostly Pezizales with their hypogeous derivatives, whereas Boletales, Gomphales, Thelephorales, Amanitaceae, Cantharellaceae, Cortinariaceae, Russulaceae, and Tricholomataceae are the most important ectomycorrhizal relationships within Hymenomycetes. ECM, as transmitting organs between soil and roots, are transporting carbohydrates for growth of mycelium and fruitbodies from roots and have to satisfy the tree’s demand for water and nutrients. The latter task particularly influences the structure of ECM as nutrients are patchily distributed in the soil and saprotrophic as well as ectomycorrhizal fungi can act as strong competitors for nutrients. In focusing these requirements, ECM developed variously structured hyphal sheaths around the roots, the so-called mantles, and differently organized mycelium that emanates from the mantle, the so-called extramatrical mycelium. The mantles can be plectenchymatous consisting of loosely woven, differently arranged hyphae or they are densely packed, forming a pseudoparenchyma similar to the epidermis of leaves. The extramatrical mycelium grows either as simple scattered hyphae from the mantle into the soil or it can be united to undifferentiated rhizomorphs with a small reach or to highly organized root-like organs with vessel-like hyphae for efficient water and nutrient transport from distances of decimeters. Cystidia, sterile and variously shaped hyphal ends, possibly appropriate for preventing animal attack, in addition, can cover mantles and rhizomorphs. Although only a limited number of species could be considered, some general conclusions are possible.

Fungal relationships and structural identity of their ectomycorrhizae

The biology of wood-rotting fungi is reviewed. Discussions are presented in taxonomy, species diversity, North American distribution, developmental response to environmental factors, edibility and toxicity, medical uses, relationships of fungi with insects and birds, the role of fungi as mycorrhiza, pathological relationships with trees, role in wood decay, and ecology. Threats to the continuing existence of these fungi as a result of increased utilization of wood as fuel are also discussed. (ACR)

Wood-Rotting Fungi of North America

Methods for characterization of ectomycorrhizas have been compiled and important features have been discussed in a recent publication (Agerer 1991a). As the characteristics have already been described in detail, the reader is referred to that article for more detailed information. In the present study, species are arranged together with regard to these features. An attempt has been made to select those characteristics which might be typical for some fungal relationships. Of course, the present treatise can only be a compilation of present-day knowledge. Further studies have to corroborate, modify or even disprove the offered, tentative conclusions. A comparison of fungal families with respect to their ectomycorrhizas was first attempted by Agerer et al. (1989). Godbout and Fortin (1985) reported common ectomycorrhizal features at the genus level.

Anatomical Characteristics of Identified Ectomycorrhizas: An Attempt Towards a Natural Classification

Knowledge of the functional diversity of ectomycorrhizas is needed to design forest management practices that sustain both commercial yield of timber and biological diversity. We surveyed the distribution of ectomycorrhizal types in logs, stumps, the forest floor and mineral soil, in mature (90-y) and old-growth (290, 440 y) stands of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco]. Ectomycorrhizal abundance (root-tips l −1 of soil) and frequency (occurrence in soil cores) were related to soil chemical characteristics and habitats. Density of ectomycorrhizal rooting was greater in the forest floor (LFH) over mineral soil (114 tips l −1 ) than in mineral soil (28) or logs (46). Logs contained more ectomycorrhizal root tips and more types of ectomycorrhizas than stumps. Piloderma fallax (Libert) Stalpers preferred woody substrate; two unidentified types, including “ Pseudotsugarhiza baculifera ” ( Piloderma ?) (Mueller, W. R. and Agerer, R. (1996) “ Pseudotsugaerhiza baculifera ”+ Pseudotsuga menziesii (Mirb.) Franco. In Descriptions of Ectomycorrhizae , ed. R. Agerer, pp. 95–100. Einhorn-Verlag, 73502 Schwabisch Gmund, Munich.), were found almost exclusively in the forest floor and coarse woody debris and another unidentified type (CDE3) was found only in mineral soil. There was little correlation between ectomycorrhizal abundance and chemical content of soil cores, perhaps due to heterogeneity of soil environment within cores. Future studies might best focus on particular fungi or microhabitats.

Distribution of ectomycorrhizas in micro-habitats in mature and old-growth stands of Douglas-fir on southeastern Vancouver Island

Three distinct Douglas-fir (Pseudotsuga menziesii) ectomycorrhizae formed by newly recognized varieties of Byssoporia (Poria) terrestris are described. They are named according to tree species and fungus as follows: P. menziesii + B. terrestris var. lilacinorosea. P. menziesii + B. terrestris var. parksii, and P. menziesii + B. terrestris var. sublutea. Each mycorrhiza is macroscopically and microscopically defined, including surrounding mycelium and attached rhizomorphs. Cultural characteristics of the three fungal symbionts grown on potato dextrose agar medium are briefly noted.

Characterization and classification of mycorrhizae of Douglas-fir. III. Pseudotsuga menziesii + Byssoporia (Poria) terrestris vars. lilacinorosea, parksii, and sublutea

B. Zak

Papers

Characterization and classification of mycorrhizae of Douglas-fir. III. Pseudotsuga menziesii + Byssoporia (Poria) terrestris vars. lilacinorosea, parksii, and sublutea