The aim of this study was to evaluate in vitro inhibitory activity of Trichoderma harzianum 127a and 127b Trichoderma harzianum. For this,two kinds of samples were made: of soil samples at different depth (5, 10 and 15 cm), and samples of the different plant organs (roots, stems and leaves). Direct and indirect confrontation techniques have served tested for different metabolites. While the technique has served, inserts evaluated the effect of the opposing competitor strains. The results of the various confrontations showed that the inhibition rate was around 90% for the two antagonistic strains T-127a and 127b-T. Furthermore, comparison tests showed a significant reduction in germination. The two strains of Trichoderma harzianum tested in this study showed a high efficiency vis-à-vis Cylindrosporium sp and Fusarium solani pathogenic lenses in the Constantine region.
