Isolation of pathogenic fungi
Fusarium oxysporum f.sp. lycopersici was isolated from stems and root tissues of infected tomato plants then sections of in lateral stem washed with three changes of sterilized distilled water and dried on filter paper. They were inoculated on PDA plates and incubated at 28 °C ±1 °C. Single spore culture was prepared[11]. Pathogenicity of the isolate toward tomato plant was estimated[12]. The isolate was maintained on PDA medium at 4°C.
Screening test for antagonism
Trichoderma spp. Isolates and Fusarium oxysporum f.sp. lycopersici were cultured in order to observe the interaction between them. They were cultivated separately for 5 days on PDA culture medium, then colonies of Trichoderma spp. and Fusarium oxysporum f.sp. lycopersici were point inoculated in pairs 3 cm apart from each other on PDA plates. The controls consisted of pure Fusarium oxysporum f.sp. lycopersici cultures. The experiment was performed three times, the plates were placed in an incubator at 28 °C ±1 °C, and the development of the colonies was observed until the controls covered the whole potato dextrose agar (PDA) surface.