The Effect of Dark Septate Endophytes on Tolerance of Tomatoes to Salinity Stress

Association of the plant with microorganisms such as dark septate endophytic fungi reduces the harmful effects of environmental stresses such as salinity. In this experiment, the effect of dark septate endophytes isolated from date palm roots on increasing salinity resistance of tomato (Lycopersicon esculentum cv. Super cheif) was investigated. The experiment was performed as a factorial in a completely randomized design with two factors including the type of isolate at 13 levels [4-B, 8-B, 10-D, 11-C, 14-A, 15-D, 16-A, 19-F, 21-A, 22-C, 22-E, 39-D, control (PDA plug)], and salinity at 3 levels (zero, 50 and 100 mM sodium chloride) with 3 replications. Tomato plants were inoculated with fungal isolates separated from date palm roots under salinity. Based on ANOVA results, in symbiosis with fungal isolates of 4-B and 11-C, the negative effects of salinity (up to 100 mM and equivalent to 9.52 dS/m) on tomato biomass were reduced. At salinity of 100 mM, 4-B had the highest plant fresh weight and 11-C had the highest plant dry weight compared to other treatments and were 55.51 and 26.55% higher than the non-inoculated treatments, respectively. By increasing the salinity level up to 100 mM, isolates of 4-B, 8-D, 10-D and 11-C had high efficiency in decreasing sodium concentration, increasing potassium concentration and potassium to sodium ratio. Symbiosis with some fungi (10-D and 8-B) caused a significant increase in phosphorus concentration (19%) compared to non-inoculated plants. At different salinity levels, isolates of 11-C, 39-D and 10-D increased the leaf relative water content. Increase in salinity up to 50 mM (equivalent to 5.44 dS/m) was associated with increased endophytic dependency and isolates of 11-C and 4-B showed the highest increase (43%) compared to other isolates.