ABSTRACT
Evolutionally, terrestrial fungi appeared at about the same time as land plants emerged. In addition to their role as saprotrophs, some fungi became intimately associated with roots of plants, enhancing their abilities to sequester nutrie nt elements; the mycorrhizal symbiotic association. Fossil records show these associations as possibly primitive endomycorrhizae in the Rhynie cherts (410-360 mya) and as ectomycorrhizae of pines in the Princeton cherts (50 mya) (Pirozynski and Malloch, 1975; Halling, 2001; Helgason and Fitter, 2005). Mycorrhizal associations now occur in some 85% of all the plant species on this planet. Recent estimates suggest that some 3617 plant species of 263 families have a mycorrhizal association (Wang and Qiu, 2006). Thus, it is regarded that the mycorrhizal condition is the most prevalent symbiotic condition on earth. Excellent discussions of mycorrhizae and mycorrhizal ecology can be found in Smith and Read (1997), Van der Heijden and Sanders (2002), and Peterson et al. (2004) and will not be elaborated upon here.
