ABSTRACT
A rbuscular mycorrhizal (AM) fungi are the predominant fungi involved in fungal root symbiosis, abundant in soils of all continents (Harley,1991). Evidence from fossil records (Stubblefield et al., 1987), morphological studies (Morton, 1990) and r DNA nucleotide sequence analysis (Simon et al., 1992) suggest that these associations co-evolved with plants. These fungi have been reported from almost all environments including aquatic (Bagyaraj et al., 1979) to xerophytic (Williams and Aldon, 1976), from lowland tropical rainforests (Janos, 1987) to high altitudes (Allen et al., 1987) and even in the canopy of epiphytes (Nadkami, 1985). Research on the ecology of these fungi has been carried out for several decades and at present over 130 species of these fungi have been identified and classified in the order Glomales belonging to the class Zygomycetes (Morton and Benny, 1990). Though these fungi occur in such diverse habitats, they benefit the host plants in several ways (Sylvia and Williams, 1992; Bagyaraj and Varma, 1994). Their role is in improving the nutritional status of hosts, particularly with respect to phosphorus
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of salt and water stress (Nelson and Safir, 1982; Sharma et al., 1992; Jarstfer and Sylvia, 1992; Auge, 2001) and improving the yield of several agricultural and horticultural crops. This has led to the initiation and advancement of research aimed at conserving these fungal associations and also directed to their inclusion as an essential component in sustainable crop production systems.
