Application of Olive-Mill-Wastewater-Compost in Combination with Symbiotic Microorganisms Improves the Physiological, Biochemical Performance and Tolerance of Tomato (Solanum lycopersicum) Under Drought Stress

Drought seriously affects the agro-physiological and biochemical functioning of plants by influencing the interactions between plants and symbiotic microorganisms. Therefore, the objective of the present study was to implement a management approach to improve tomato growth, and drought tolerance using arbuscular mycorrhizal fungi (AMF) (pure strain (M) and consortium (M′)), and/or plant growth-promoting-rhizobacteria (Actinomycetes (A) and consortium with two bacteria Z2 and Z4 (B), and/or Olive-Mill-Wastewater-compost (OMWW-compost (C)). The potential for changes in physiological (stomatal conductance, chlorophyll fluorescence, photosynthetic pigments) and biochemical (sugar, protein, hydrogen peroxide (H2O2), malondialdehyde (MDA), phenols, and antioxidant enzymes) functioning in response to water stress was analyzed. Therefore, under 35% field capacity (FC), the application of AMF (M or M′)/PGPR (A and B) amended with compost stimulated biomass and improved stomatal conductance, chlorophyll and carotenoid contents and photosynthetic efficiency to a greater extent than in uninoculated and/or unamended plants. The compost application with double inoculation including M′A (CM′A) significantly improved sugar concentrations in leaves and roots by 34% and 30% as well as enhanced antioxidant activities notably catalase (CAT), polyphenoloxidase (PPO) peroxidase (POX) and superoxide dismutase activities of about 92%, 177%, 84% and 79%, respectively. The dual inoculation together with compost (CM′A) and (CM′B) resulted in a significant reduction of H2O2 contents by 14% and 13% and MDA by 93% and 92%, respectively. The application of locally produced compost with dual combinations of bacteria can overcome the challenges of water stress by improving the physiological, biochemical and tolerance of tomato.