Abstract
Forty three halotolerant bacteria, growing on nutrient agar mediumsupplemented with 10% NaCI were isolated from barley rhizosphere in Taif province. Based on in vitro tests, four isolates possessed activities of plant growth promoting rhizobacteria (PGPR) and two possessed higher activities. Based on morphological, biochemical and molecular characterization, they were identified. Phylogenetic analysis based on 16S rRNA analysis showed that all isolates belonged to Bacillus spp. For in vivo studies, pots were singly or dually inoculated with aqueous suspension ofthe most potent PGPR; Bacillus subtilis YHSA20 or/and Bacillus sp.YHSA34. Barley (Hordeum vulgare L.) seedlings were transplanted and 15 days old plants received 0, 100, 200, 300 and 400 mMNaCI, watered and received Hogland solution, each once a week and grown under greenhouse conditions for 12 weeks. Salt stress reduced the plant growth, leaf photosynthetic pigments, and caused considerable changes in proline, total phenolic compounds and peroxidase. Bacteria treated plants significantly improved photosynthetic pigments and plant growth, under salt stress. The bacteria ameliorated the salt stress, as indicated by increasing praline content and activities of peroxidase, in spite of lowering total phenolic compounds. This study indicates that hese bacteria have potential to alleviate the salt stress and enhance plant growth under saline habitats, through direct and indirect mechanisms and could be appropriate bioinoculants under such conditions.