Microbial populations are key component of soil plant system where they are immense in a network of interactions affecting plant development. Several symbiotic groups, phosphorus solubilizers, plant growth promoters and other such beneficial important micro- organisms are reported from different soils. Balanced microbial system contributes to the sustainability in agriculture, horticulture, forestry and range management. In this regard, an excellent example of microbe- plant mutualism is ‘Mycorrhiza’. The mycorrhizal symbiotic association appears to have evolved with plants since the colonization of dry land by plant began as a survival mechanism for fungi and higher plants, thus allowing each to survive in the existing environment of low temperature, low soil fertility, periodic drought, diseases, extreme environments and other stress situations. Among the different types of mycorrhiza, arbuscular mycorrhizae (AM) are the important beneficial micro- organisms of the soil edaphon in most agro-ecosystems. AM, the mother of plant root endosymbiosis, is a wide spread mutualistic symbiosis between land plants and fungi of the phylum Glomeromycota. AM plant symbiosis to be established, molecular signaling events must occur that lead to various physiological and anatomical changes in both symbionts. Horticultural crop and flowers have been used as the host plants in several experimental tests for application of arbuscular mycorrhizal fungi. Mycorrhizal fungi can stimulate horticultural plants and vegetable crop’s growth especially in the soils with lower fertility and the positive effect of mycorrhiza on plants mainly due to improved phosphorus uptake has been documented. AMF enable their host plant to tolerate environmental extremes such as nitrogen and phosphorus deficiency, drought, low pH, soil pollution, negative effects of some root pathogens etc.