Ectendomycorrhizal associations - characteristics and functions

Mycorrhizal symbioses are widespread mutualistic associations of many plant hosts found in many habitats. One type of putative mycorrhizal association , ectendomycorrhiza, is confined to Pinus and Larix spp. and is common in c onifer nurseries and in disturbed habitats. This association is characteriz ed by the unique combination of a fungal mantle, Hartig net, and intracellu lar hyphae, the latter forming soon after Hartig net development. Many repo rts of the occurrence of ectendomycorrhizas from field-collected specimens are likely erroneous and instead may represent senescent ectomycorrhizas. T he fungus species involved in the formation of ectendomycorrhizas were init ially called E-strain fungi and their identification was based on character istics of hyphae and chlamydospores. With the discovery of teleomorphs for some of these fungi, they were found to be ascomycetes. More recently, mole cular methods have been used to clarify their systematics and phylogeny and it is apparent that most of the isolates belong to two species, Wilcoxina mikolae and Wilcoxina rehmii. Two species of dematiaceous fungi and a membe r of the Pezizales, Sphaerosporella brunnea, also have been reported to for m ectendomycorrhizas. These fungi can form ectendomycorrhizas with their ho sts over a broad pH range and may utilize many substrates as a carbon sourc e. Ectendomycorrhizas may be important in the revegetation of disturbed sit es and in the establishment of conifer seedlings in post-fire situations.