ABSTRACT
Arbuscular mycorrhizal (AM) fungi by virtue of their ubiquity and their key role as biofertilizers, bioregulators, and bioprotectors are essential components of the soil biota (Dodds, 2000). The production of many agricultural, horticultural, and fruit crops in soil are depend ent on the formation of AM fungi, making this symbiosis an essential factor in low-input sustainable agriculture. AM fungi are commonly described as “the universal plant symbiont,” and are found in practi cally every taxonomic group of plants. About 80 percent of all terres trial plant species form this type of symbiosis. Widespread distribu tion in habitats and host species, symbiotic existence, enhancement of host growth and protection, obligate nature and specificity for hosts, and positive and negative interaction with other rhizosphere microbes are a few characteristics of AM fungi that lead to the study of these microorganisms. Arbuscular mycorrhizal fungi are widely distributed and usually abundant in soil (Mukerji and Rani, 1989). Their population varies greatly in size and composition according to habitat, and type of soil and vegetation. Because of their beneficial ef fect on plant growth, AM fungi are important for natural and man aged ecosystems (Brundrett et al., 1996).
