LAUSR

ABSTRACT In the Mediterranean climate, plants, e.g., Quercus brantii Lindl, have evolved and adapted to bear up low soil-water and soil-phosphorus conditions. Quercus brantii Lindl. is a dominant tree species thorough Zagros Mediterranean forests. Phosphate-solubilizing bacteria (PSB) play crucial role in the plant growth enhancement by solubilizing insoluble soil-phosphate. In the present study, the effects of two indigenous PSB strains, e.g., Microbacterium sp. (M.) and Streptomyces sp. (S.) were individually and combined evaluated on growth and physiological traits of Quercus brantii. seedlings under different water stress treatments. Results showed that maximum P- solubilization rate was observed by M. strain. Results also revealed that water stress increased electrolyte leakage and reduced relative water content in all plant compartments as well as growth parameters. Two PSB strains individually and in combination significantly enhanced growth and physiological traits of seedlings under both irrigation treatments compared with the non-inoculated seedlings. The M. strain showed higher potential for increasing of root length, weight and RWC compare to other PSB strain. Finally, the results suggested that application of isolated indigenous PSBs in reforestation could help to cope with the drought conditions in semi-arid Mediterranean Zagros forests by increasing of root and improving of oak seedlings growth.