Morphotyping and Molecular Methods to Characterize Ectomycorrhizal Roots and Hyphae in Soil

Abstract

At the interface between plants and soils, ectomycorrhizal (ECM) fungi explore soils, acquire resources, transfer resources to plants, and acquire carbon from plants. Mycorrhizas enhance plant survival, nutrition and growth and play key roles in ecosystems processes such as decomposition, nutrient cycling, soil carbon storage, productivity and sustainability. Mycorrhizas are critical for plant colonization of new soils (e.g. mine spoils, volcanic deposits, glacial moraines). ECM diversity ensures plant reestablishment after disturbance and can enhance survival and growth of trees in reforestation. ECM fungi can promote fine root development as well as produce antibiotics, hormones and vitamins. Mycorrhizal associations may help protect roots from pathogens and moderate effects of heavy metals and toxins. Many environmental problems may be alleviated by mycorrhizas – problems such as pollution, erosion, soil degradation, climate change, degradation of natural resources, and poor land use management. Mycorrhizal abilities to carry out important functions are linked to diversity. ECM diversity is large and documented in many ecosystems, particularly coniferous ecosystems (Gehring et al. 1998; Goodman and Trofymow 1998; Kranabetter and Wylie 1998; van der Heijden et al. 1998; Stendell et al. 1999; Bidartondo et al. 2000). This ECM diversity has been based on surveys of fruiting bodies, but is now based on more recent methods – morphotyping (microscopic observations) and phylotyping (molecular characterization). An advantage of fruiting body surveys is ease of collection and identification based on morphology; a disadvantage is the assumption that fungi fruiting in an area also form ectomycorrhizas on nearby roots. Clearly identification of ectomycorrhizas on roots is preferable. However there are difficulties in ECM identification – complex sampling design and