This study focuses on the isolation of Trichoderma strains from lichens collected from Acacia trees located in Misserghine, Algeria, the evaluation of their tolerance to abiotic stresses at different pH (4.5, 6 and 8) and temperature (15°C, 20°C, 25°C and 35°C) and their potential use to promote the germination and growth of tomato plants (Solanum lycopersicum). Five Trichoderma strains were isolated and morphologically identified. The results showed that the optimal growth of strains was obtained at pH 4.5 and 25°C with variability between strains, notably S5 which showed better tolerance to alkaline pH. The effect of these strains on the germination of tomato plants showed that the majority of the strains significantly improved the germination rate (80 to 86% versus 70% for the control) and the seed vigor index. Strains S2 and S4 recorded the best results almost doubling the vigor index compared to the control. The evaluation of vegetative growth of tomato plants after four weeks confirmed these positive results, especially for strain S4 which significantly increased the length of roots (7.84 cm) and stems (16.38 cm) compared to the control (3 cm and 13.98 cm respectively). However, strain S3 showed negative effects on plant development by reducing the seed vigor index to 314,88 compared to the control with S.V.I of 756, decreasing the stems length to 9.42 cm and exhibiting no significant effect on root growth.