ABSTRACT
Phytopathogenic fungi are generally small and more complex organisms than bacteria. They are, sometimes visible to the naked eye but more often with the aid of a micro scope. They are characterized by the forma tion of free or interlaced filaments (hyphae), all of which constitute the ‘mycelium’. This can be coenocytic (without cell walls, as Pythium spp., Phytophthora infestans, and other Phytophthora spp.,1 Rhizopus stolonifer), or with cell walls (Alternaria tomatophila, Stemphylium spp., Botrytis cinerea, Pyrenochaeta lycopersici, Sclerotinia spp., Sclerotium rolfsii, Rhizoctonia solani).
