Isolation and characterization of PGPR from the rhizosphere of the Avena sativa in saline-alkali soil

Two strains of plant growth-promoting rhizobacteria(PGPR) containing ACC deaminase,A-2 and A-4 were isolated from saline-alkali rhizosphere soil of Avena sativa,based upon their ability to utilize 1-aminocyclopropane-1-carboxylate(ACC) as a sole nitrogen source.Using morphology,physiological biochemical characteristics and 16S rDNA analysis,strain A-2 was identified as Enterobacter sp.and A-4 was confirmed as Pseudomonas sp..The ACC deaminase activity of A-2 and A-4 were(1.89±0.12) μmol α-KA/(mg Pr·h) and(2.63±0.12) μmol α-KA/(mg Pr·h),respectively.When the concentration of L-Trp increased,the IAA synthesis of A-2 increased,while that of A-4 did not change significantly.The ability of A-2 to synthesize siderophore was greater than that of A-4.The height of oat plants treated with A-2 and A-4 were from 12.24 cm up to 13.98 and 14.07 cm,the plant fresh weights were from 34.285 g up to 35.012 and 35.102 g,respectively.The length of roots were from 14.13 cm up to 16.23 and 17.60 cm,and root fresh weights were from 7.790 g up to 8.065 and 8.187 g,respectively.These results suggest that strains A-2 and A-4 contain ACC deaminase that can increase resistance in oat to saline-alkali stress.