ABSTRACT
Fusarium oxysporum is a causative agent of wilt disease in a wide range of economically important crops (Booth, 1984). Fusarium oxysporum Schlechtend. Fr. is an anamorphic species circumscribed by different morphological criteria: principally the shape and size of the macroconidium,
the presence or absence of microconidia and chlamydospores, colony colour, and conidiophore structure (Windels 1992). The diffi culty in delineating species based on these features is evidenced by the different systems that have been proposed, recognizing anywhere from 30 to 101 species (Nelson et al. 1983). F. oxysporum is more commonly isolated fungi from asymptomatic roots of crop plants (Gordon and Martyn 1997). F. oxysporum has a well-documented ability to persist without recourse to pathogenesis. Both pathogenic and non-pathogenic strains of F. oxysporum are found in agricultural soils throughout the world and have received a lot of attention from researchers. However, substantial populations of F. oxysporum are also found in many native plant communities, in soils that have never been cultivated (Gordon and Martyn 1997). This group of cosmopolitan, soil borne fi lamentous fungi is economically important because many members are the causal agents of vascular wilt or root rot diseases in agricultural and ornamental crops throughout the world (Woo et al. 1998). The typical symptoms caused by Fusarium oxysporum include wilting, yellowing and xylem discoloration.
