Characterization of Plant Growth Promoting Bacteria (PGPB) as a Tool for Alleviation Salt Stress of Medicinal Plants

Abstract

Salinity and drought are two of the most serious abiotic problems for agriculture productivity worldwide. Halophilic and halo-tolerant plant growth promoting rhizobacteria (HT-PGPR) are as an efficient eco-friendly tool to alleviate salt and drought stress. In this study, 40 isolates
were isolated from rhizospher of 5 wild medicinal plants (Zygophyllum album, Salsola tetrandra, Limoniastrum monopetalum, Halocnemum strobilaceum and Sarcocornia fruticosa) grown at coastal ooletic sand dunes habitat at Mersa Matruh, Cleopatra, GPS reading is 31°
22.460 N, 27°11.009 E, Matrouh government. For initial screening, the results showed that 17 isolates gave positive reaction for IAA detection. While 30 isolates can produce exopolysaccharides, as well as, two different isolates are positive for phosphors (P) and potassium (K) solubiliztion. The forty isolates had different growth on nutrient agar medium supplemented with NaCl ranged from 3-15%. The efficient isolates (18) from the first screening were tested for their biological characteristics to mitigate salt stress; proline, total sugar, IAA production, antioxidant activity and P, k solubilization. The most efficient three isolates namely, Li1, Li8 and Sar13 were identified by 16s rRNA gene. These three strains are study their properties to alleviate the drought stress by grown them in different concentrations of 6000 Polyethylene glycol (PEG) and recorded the optical density (O.D) at 600 nm.