ABSTRACT
Degradation of nature and agroecosystems, resulting from anthropogenic impacts, is associated with disturbances in plant communities but also with a loss of physicochemical and biological soil properties such as plant nutrient availability, organic matter, and microbial activities (Barea and Jeffries, 1995). In recent years, increasing evidence has suggested that the microbial communities of soil and plants play a key ecological role in the development of sustainable agriculture. Among the microorganisms living in the rhizosphere of plants, mycorrhizal fungi are usually considered essential components of sustainable soil-plant systems (Bethlenfalvay and Linderman, 1992; Hooker and Black, 1995; Van der Hejden et al., 1998). This mycorrhizal symbiosis is being actively studied for its beneficial effect on plant growth and its potential use in agriculture and forestry. Mycorrhizal fungi improve uptake of plant minerals, such as phosphorus (Sanders and Tinker, 1971; Bolan, 1991; Plenchette and Fardeau, 1998), micronutrients (Cooper, 1984; Kucey and Janzen, 1987; Bürkert and Robson, 1994), and nitrogen (Barea et al., 1991). Mycorrhizal symbiosis can also enhance water absorption (Sieverding, 1991; George et al., 1992) and improve plant health with antagonism against some pathogens (Dehne, 1982; Duponnois and Cadet, 1994). In addition, mycorrhizal fungi play a significant role on soil structure in the formation and stability of soil aggregates (Hamel et al., 1997; Wright and Upadhyaya, 1998).
