Effect of Rhizobacteria On Drought Stress Tolerance of Tomato Plants at Vegetative and Fruiting Growth Stages

This study including two successive experiments was conducted to evaluate the effect of native rhizobacteria (RB) strains on drought tolerance of tomato plants at the vegetative and fruiting growth stages. The first experiment was conducted in the growth room by growing plants in nutrient solution under polyethylene glycol induced drought stress, which initiated 7 days after planting and lasted 8 days by increasing the osmotic stress gradually every 48 h from Ψ_s = −0.25 to −1.00 MPa. Among the 12 RB tested, RB isolates 113 (Bacillus megaterium isolate NUC) and 377 (Bacillus cereus strain BBS7) were selected according to principal component analysis for testing in long term plant production. The second experiment was conducted in the greenhouse by growing plants in perlite filled pots for 128 days after transplanting. Irrigation was based on the water consumption of the plants, and the plants were irrigated to cover well-watered (100% FC) or drought (50% FC) of this amount. For both experiments, seeds were inoculated with the RB strains before sowing. RB inoculation increased plant growth, leaf pigment contents, antioxidant enzyme activities and ascorbic acid level, but reduced malondialdehyde levels in tomato plants under drought stress. The marketable yield was increased 8.7 and 10.6% in the absence of water stress, and 70.2 and 59.9% under water stress by RB 113 and RB 377, respectively.