Twelve fungal isolates were obtained from roots of field-grown Rhododendron plants. One of these produced ericoid mycorrhizal roots within 5 days when reassociated with Rhododendron plantlets under aseptic conditions. The organism was identified as Oidiodendron maius. A characteristic feature of this organism was production of conidiophores in both pure culture and in association with root cells of the host. Ultrastructural observations confirmed its mycorrhizal status and showed intracellular hyphae surrounded by an interfacial zone and plasma membrane. Hyphae were found in close association with the host nucleus and cytoplasmic organelles. Pure isolates derived from diverse alternative sources were also tested for mycorrhizal formation with Rhododendron under aseptic conditions. Thus, Pezizella ericae obtained from Calluna vulgaris produced mycorrhizal infections after 10 days of culture, whereas O. maius from Sitka spruce and Oidiodendron griseum from wood pulp failed to form mycorrhizas.

The effect of different culture conditions on growth and production of fomannoxin and the sesquiterpene phytotoxin fomannosin by a single isolate of Fomes annosus was studied. Whereas fomannoxin was produced by actively growing hyphae, fomannosin production was associated with the declinning growth phase of the fungus. The presence of fomannoxin in chloroform extracts from the stained stein heartwood zone of Fomes annosus diseased Sitka spruce trees was established. Fomannosin however was not detected. Toxicity of fomannoxin to germinating seeds and young seedlings of Sitka spruce was demonstrated.

No abstract

Identity of mycorrhizas and isolation of symbionts and associated fungi from Sitka spruce growing in pure and mixed stands with either Japanese larch or Lodgepole pine are described and com ared More mycorrhizal types and sporocarps of the Agaricales were collected from mixed stanis. Mycorrhizas of Lacturius rufus, Puxillus involutus and Suillus spp. were more revalent on roots from mixed stands. The most common unidentified mycorrhizal t pe (type B)Rad features similar to synthesized mycorrhizas of two Basidiomycete isolates. SuilLs grevillei and three unidentified types were associated specifically with Japanese larch. The main associating fun i were Oidiodendron sp. and M celium rudicis utrovirens. The association of a "nurse" tree witE Sitka spruce provides a more c&erse rnycorrhizal flora, the majority of which are shared between the tree species.

Identity of mycorrhizas and isolation of symbionts and associated fungi from Sitka spruce growing in pure and mixed stands with either Japanese larch or Lodgepole pine are described and com ared More mycorrhizal types and sporocarps of the Agaricales were collected from mixed stanis. Mycorrhizas of Lacturius rufus, Puxillus involutus and Suillus spp. were more revalent on roots from mixed stands. The most common unidentified mycorrhizal t pe (type B)Rad features similar to synthesized mycorrhizas of two Basidiomycete isolates. SuilLs grevillei and three unidentified types were associated specifically with Japanese larch. The main associating fun i were Oidiodendron sp. and M celium rudicis utrovirens. The association of a "nurse" tree witE Sitka spruce provides a more c&erse rnycorrhizal flora, the majority of which are shared between the tree species.