Fungi play a central role in many soil microbiological processes, influencing soil fertility, decomposition, the cycling of minerals and organic matter, plant health and nutrition. Read and Perez-Moreno (2003), note that they also influence the structure and functioning of plant communities and soil ecosystems. Fungi are immensely diverse, both structurally and functionally and have adopted different trophic strategies, occurring as saprotrophs, symionts and pathogens. Leake (2005), sayings about “soil fungi”, the filamentous growth habit of many fungi, coupled with their different trophic strategies, implies that individual fungi can often simultaneously colonize different substrates, such as living or dead plant tissue, coarse wood

debris, soil animals and mineral substrates in addition to the soil itself. Together with animals and plants, fungi represent one of three major evolutionary branches of multi-cellular organisms, and their uniqueness in reflected in the fact that they have the traditional status of a kingdom (the Mycota). According to Hawksworth. (2001), the diversity of fungi is high and, although only 75,000 species have been described so far, it is likely that this represents only 5% of the true number of fungi species, which is estimated to be 1.5 million.

Despite this structural and functional diversity, all fungi share certain common features, such as the fact that they are eukaryotic, contain a range of membrane- bound organelles such mitochondria and vesicles, and possess membrane-bound nuclei containing several chromosomes, they are heterotrophs. requiring external carbon sources (Johnson et al., 2005). They also typically display filamentous growth as a result of their hyphae, which exhibit apical

growth; thus, they are able to colonize new substrates. In forming a mycelium by repeated branching, some fungi such as singled celled yeasts exhibit dimorphic growth and can reproduce in liquids by budding as well as by colonizing other substrates through mycelia growth. Unlike other eukaryotes fungi typically have haploid nuclei; however, the hyphae may have several nuclei in each compartment .Moreover, many budding yeasts are diploid. Fungi characteristically produce spore and many can reproduce both sexually and asexually. They have cell walls composed of polymers of glucose, such as chitins and glucans, and they secrete enzymes that degrade complex polymers at their hyphal tips, allowing them to take up smaller molecules being heterotrophic. Johnson et al., (2005) reported that fungi require external carbon for energy and cellular synthesis. Three major groups - saprotrophs, pathogens and symboiont can be distinguished in accordance with the trophic strategies adopted to acquire the organic compounds (Leake, 2005). Apart from their impact on natural terrestrial ecosystem (Gadd et al.,2006), soil fungi have important, and still largely unexploited, application in the biological control of pathogens, the bioremediation of polluting compounds and the biofertilization of soil (Gadd, 2001). Further, soil fungi produce a large range of secondary metabolites with potential for medical biocontrol, or environmental applications. Butt et al., (2001), including antibiotics such as penicillins and cephalosporins, such as organic acid and siderophores, may be involved in the release and sequestration of mineral nutrients as well as in antagonistic interactions with other organisms. In addition, fungi secrete a wide variety of enzymes used in either pathogenic interactions or in the degradation of plant litter and wood substrates (Lindahl and Finlay, 2006). Some of these enzymes find important applications in bioremediation of organic pollutants. Symiotic mycorrhizal fungi produce mycelia by growing from the roots of their host plants into the surrounding soil. This connects them to the heterogeneously distributed nutrient required for their growth, enabling the flow of energy-rich compounds required for nutrient mobilization while simultaneously providing conduits for the translocation of the mobilized products back to their hosts.