Effects of plant growth-promoting rhizobacteria on the seedling growth of oat and annual ryegrass under salt stress

Four strains of plant growth-promoting bacteria (PGPR) were isolated from the rhizosphere of salty plants, based on the ability to utilize the compound1-aminocyclopropane-1-carboxylic acid (ACC) as a sole nitrogen source. These four bacterial isolates, especially Pseudomonas sp. S1, alleviated greatly salt stress and promoted significantly the seedling growth of oat and annual ryegrass under either 5 or 10 g/kg NaCl stress in gnotobiotic growth pouch assay. Compared with control (no NaCl), more plant promotion was observed under 10 g/kg NaCl stress. The greatly significant positive correlations between ACC deaminase activity of four bacterial isolates and plant growth parameters (root length and shoot length) were observed (Pearson correlation co-efficients > 0.81). The results may imply that inoculation with ACC deaminase-containing PGPR may serve as an environmentally-friendly and economical alternative to the amelioration of increasingly saline soils.