Plant Growth Promoting Characteristics in Some Flavobacterium spp. Isolated from Soils of Iran

Plant growth promoting rhizobacteria (PGPR) is referred to a heterogeneous group of beneficial rhizospherebacteria that could enhance plant yield through one or more mechanisms. Flavobacterium has been noted asPGPR in almost all review articles. However, there are a few studies regarding plant growth promotion imposedby them. Some of Plant growth promoting characteristics such as Phosphate solubilizing capacity, ability to useof 1-Amino Cyclopropan-1-Carboxylate (ACC) as sole nitrogen source and production of auxin, siderophore, salicylic acid, chitinase and hydrogen cyanide were evaluated in forty-four flavobacteria isolated fromrhizosphere of wheat. Results showed that none of the isolates were able to produce siderophore, salicylic acidand chitinase and they were not able to use ACC as well. Determining the siderophore showed that none isolatesdid not grow on Chrome Azurol S (CAS) Agar medium. The results of this part were further analyzed usingCAS Agar Diffusion (CASAD) method, but the results were also negative. HCN production was observed in allisolates, but in lowest limit. Thirty-four isolates were capable to solubilize insoluble inorganic Phosphate (P) sources. The average rate of P-solubilization was 3.54 μg Pml-1, ranging from zero to 37.48 μgPml-1. There wasa significant negative correlation (r = -0.81**) between solubilized P and the final pH of the growth medium. Inthis study, all the isolates were able to produce auxin, ranging from 0.27 to 12.03 μgml-1 averaged by 2.03. Considering the ability of the isolates to produce auxin and for P-solubilization, it is necessary to evaluate theireffect on growth and yield of different crop plants.