ABSTRACT
Organisms which derive the susbtrate materials needed for growth and reproduction from living plants (host or suscept) are called parasites. There are three extreme lifestyles for pathogens: biotrophic, hemibiotrophic and necrotrophic. Purely biotrophic pathogens are typically obligate parasites, although necrotrophic pathogens can also exist as saprophytes. The roots of most plants are colonized by symbiotic fungi to form mycorrhiza, which play a critical role in the capture of nutrients from the soil and therefore in plant nutrition. Mycorrhizas are commonly divided into ectomycorrhizas and endomycorrhizas ecto means outside the root, endo means inside. The two types are differentiated by the fact that the hyphae of ectomycorrhizal fungi do not penetrate individual cells within the root, while the hyphae of endomycorrhizal fungi penetrate the cell wall and invaginate the cell membrane.
