Effects of Trichoderma isolates on tomato growth and inducing its tolerance to water-deficit stress

The fungal species belonging to the Trichoderma genus are the most promising microorganisms which improve plant growth by enhancing nutrient uptake and preventing them against environmental biotic and abiotic stresses. This study was aimed to evaluate the effects of three efficient Trichoderma isolates on tomato growth under water-deficit stress. Ten isolates of Trichoderma were in vitro assayed for auxin production, phosphate solubilizing activity and siderophore production traits, and three efficient isolates were selected for pot culture experiment according to the above assessments. Treatments including inoculation with T 1 ( Trichoderma longibrachiatum KH), T 2 ( T . longibrachiatum MA), T 3 ( T . harzianum ), NT 1 (negative control; without fungi) and NT 2 (positive control; without fungi but with chemical fertilizers) at three soil moisture levels of W 0 (no water-deficit stress), W 1 (medium stress) and W 2 (severe stress) were applied to the pots on seedling transplanting. The results revealed that the shoot and root dry matter, root volume, leaf water potential and stomatal conductance decreased as water-deficit stress increased. However, the decrease was significantly lower in fungal treatments than non-inoculated ones. Inoculations with T 1 , T 2 or T 3 increased shoot dry weight by 97.2, 17.2 and 18.96% compared to the positive control (NT 2 ) and by 32.81, 19.41 and 20.42% compared to the negative control (NT 1 ), respectively. The highest root volume was recorded in T 1 inoculation. This fungus increased root volume by 91.74% and 96.37% compared to the NT 1 and NT 2 controls, respectively. Moreover, the T 1 inoculation enhanced shoot potassium uptake by 37.23 and 34.36% and that of root by 63.25% and 62.02% compared to the NT 1 and NT 2 controls, respectively.