ABSTRACT

A study was conducted on the development of rhizosphere consortia for seed treatment to improve the growth of soybean. The PGPR strains used were collected from the Institute of Organic Farming, UAS, Dharwad. The main aim was to standardize the single culture medium and also to identify the optimum number of PGPR strains to formulate consortia. Morphological, biochemical and functional characterisation tests was carried out. The strains were found to be compatible. Luria bertani broth as a common medium with varied concentrations of additives such as Polyethylene Glycol, Glycerol, Gum arabica and Ascorbic acid for each of the eight PGPR strains were standardized. Further, based on the population of individual PGPR strain, seventeen PGPR formulations with the combinations of Bradyrhizobium japonicum(SB-120), Pseudomonas striata (PSB), Bacillus sp.(KSB), Zincsolubilizing bacterium(ZnSB), Silica solubilizing bacterium(SiSB), Actinobacterium(JK-16), Pink pigmented methylotroph(PPFM-33) and Lactic acid bacterium(LAB-75) as liquid formulations were developed and a green house pot experiment was conducted to test the effect of different PGPR consortia growth and yield parameters of soybean. Among the different treatments, RDF+rhizosphere consortia recorded the maximum plant height (48.24 cm), number of leaves (28 trifoliate leaves), root length (20.15 cm/plant), relative chlorophyll content (46.00), number of nodules (15.75 nodules/plant), number of pods (17.50 pods/plant) and total dry matter production (33.55 g/plant) of soybean plant. The effect of rhizosphere consortia of eight strains was found to be on par with consortia of six PGPR strains in T16 (RDF+SB-120+PSB+KSB+ZnSB+SiSB+LAB-75), T15 (RDF+SB-120+PSB+ KSB+ZnSB+SiSB+PPFM-33) and T17 (RDF+SB-120+PSB+KSB+ZnSB+SiSB+JK-16) with respect to all parameters. This study showed that instead of using different culture media for growth of individual PGPR strains, Luria Bertani broth seem to be a single common culture medium. Consortium of six PGPR strains was able to give equivalent effects across all parameters compared to consortium of eight PGPR strains.