The Isolation and Characterization of Phosphate Solubilizing Bacteria from the Onion Rhizosphere and Their Effect on Onion Growth

Abstract

In this study 269 phosphate solubilizing bacteria (PSB) strains were isolated from onions rhizosphere. The 15 most efficient PSB were selected. Based on BIOLOG profiling and the LOPAT test system, the strains were identified as Enterobacter cloacae (7), Yersinia intermedia, Pantoea agglomerans, Bacillus subtilis(2), Bacillus pumilius, Lysinibacillus sphaericus and Bacillus atrophaeus(2). The PSB effect on onion growth was investigated under greenhouse conditions. These PSB increased plant height (11.7 to 38.8%), the number of leaves (3 to 70%), the bulb diameter (6.4 to 64.5%), the average root length (2.6 to 44.7%), the fresh weight of the bulb (2.9 to 34.1%) and the dry weight of the bulb (1.5 to 40.6%) when compared to the negative control. Among these strains the most effective inoculants were the highest P solubizing E.cloacae EB-14 and E. cloacae OB-169 strains, which significantly increased all parameters compared to the commercial plant activator ISR 2000. These results demonstrated the potential use of these PSB as inoculants for onion growth.