Amelioration of Salt Stress on Oat Seedlings by ACC Deaminase-Containing Plant Growth-Promoting Rhizobacteria

摘要

Four strains of plant growth-promoting rhizobacteria (PGPR) were isolated from the rhizosphere of salty plants, based on the ability to utilize the compound 1-aminocyclopropane-1-carboxylic acid (ACC) as a sole nitrogen source. These four isolates were identified as Pseudomonas sp. S1, Citrobacter sp. S2, Enterobacter sp. S3 and Klebsiella sp. S4 by 16srDNA sequence analysis. These four bacterial isolates showed significant amelioration of either 0.5% or 1% NaCl (w/w) stress on oat seedlings in either gnotobiotic growth pouch assay or unsterilized soil pot trial. Among these four bacterial isolates, S1 was the most effective, and followed by S3 and S4. Compared with control (0% NaCl), more plant growth promotion was observed under 1% NaCl stress. Under 1% NaCl, the average root length and root dry weight of oat seedlings inoculated with S1 increased over uninoculation by 137.2% and 96.2% in gnotobiotic growth pouch assay, and by 127.2% and 158.3% in soil pot trial, respectively. The greatly significant positive correlations between ACC deaminase activity and plant growth parameters tested (root length, root fresh weight, root dry weight and shoot length) under either 0.5% or 1% NaCl stress were observed (Pearson correlation coefficients > 0.93). 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.