Plant Growth Promoting Bacteria (PGPB) may establish close associations with plant to protect it from abiotic stresses and enhance its growth. This study evaluated the effect of PGPB on plant’s physiological and growing parameters as well as on soil physical properties, under different water stress levels. The experiment has been conducted in experimental greenhouse, inoculating two bacteria strains (Micrococcus yunnanensis (M1); Pseudomonas stutzeri (SR7-77)) on tomato plants and applying three water regimes: full irrigation (100% Pot Capacity - PC) and two deficit regimes at 75% and 50% PC. Overall, the two strains showed a significance decrease in soil permeability comparing to the control, but they made soil water availability (AW) more efficient under water stress periods, besides increasing root surface density, especially for SR7-77.
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Furthermore, the combination of bacteria and specific water regimes had a significance response on shoot and root dry weight ratio and on leaf water use efficiency (WUE), whereas, they did not show positive effect on other parameters as yield but in terms of water regime it shows a slight effect of (M1) at 75% and 50% PC comparing to the control. Due to uncontrolled factors, the bacteria’s tests compared to the control showed a high variability that often influences the significance. Once the two variability (control and bacteria) were made comparable such parameters as AW and WUE showed a high significance.
