Characterization of siderophore producing bacterial strain Pseudomonas fluorescens Mst 8.2 as plant growth promoting and biocontrol agent in wheat

A set of 28 Pseudomonas bacterial strains were examined for siderophore production by chrome azurol sulphonate (CAS) assay. Among the 28 strains tested, 14 were found to be siderophore producers. These strains were evaluated for their biocontrol potential against Rhizoctonia solani using various dual culture assays. The role of siderophores in the inhibition of R. solani was confirmed by iron chloride (FeCl3) experiment. The eight strains that showed best antagonism were found to have the potential of nitrogen fixation, phosphate solubilization, indole acetic acid, hydrolytic enzymes, hydrogen cyanide and antibiotics production. Spectrochemical analysis of siderophores indicated that all the bacterial strains produce catecholate siderophores. Our data demonstrated that bacterial strain Mst 8.2 produces more than one antifungal agents but the siderophore production is the key mechanism involved in the antagonism. Bacterial strains MS-3y, Mst 8.2 and Mst 7.4 were the most effective with more than 70% disease reduction in plant growth of wheat. The complete 16S rRNA gene sequence analysis demonstrated that Mst 8.2 is a Pseudomonas fluorescens strain. In conclusion, Mst 8.2 with its multi-mechanisms of defense has excellent potential to be used as successful biocontrol agent against R. solani root rot disease in wheat.