Antagonistic properties of four isolates of Trichoderma against fungal pathogen Rhizoctonia solani were investigated. The addition of T. harzianum strain PBG to the potground protected cucumber plants against root rot caused by R. solani and increased the weight of cucumber plants growing in potground with pathogen by 19-26%, compared to infested control. All Trichoderma strains (T. harzianum strain PBG; T. longibrachiatum szczep T2; T. harzianum strain T4 and Trichoderma sp. strain T6) indicated positive effect on lettuce growth in the greenhouse experiment. They increased the number of germinated seeds and the average mass of seedlings. The highest growth stimulation of the lettuce was observed using Trichoderma strain T6 and T. harzianum strain PBG, respectively 49% and 33%, when compared to the control treatment. Moreover, these isolates most efficiently protected lettuce seedlings against R. solani. The application of the combinations of four Trichoderma together did not increase the protective effect against R. solani.
