Phosphate-solubilizing peanut associated bacteria: screening for plant growth-promoting activities

In the present study, attempts were made to identify the potential of bacterial strains for promoting Arachis hypogaea L. growth. Four hundred and thirty three bacteria were isolated from rhizosphere, phyllosphere and plant tissues from peanuts cultivated in the producing area of Cordoba, Argentina. From this collection, 37 epiphytic isolates and 73 endophytic isolates were selected on the basis of tricalcium phosphate solubilizing activity. These isolates were further tested for other plant growth-promoting attributes and some of them evaluated to examine the effect of inoculation on peanut growth. Siderophore production was observed in a high percentage of the isolates, especially in the root nodule endophytes. Antibiosis was evaluated against the phytopathogen fungus Sclerotinia minor and S. Sclerotiorum. Endophytes from nodules showed the highest levels of fungal growth inhibition. A low number of isolates was able to produce auxin like molecules and inoculation of peanut seedlings with these bacteria showed variability on seed germination enhancement. Isolate J49, identified to belong to genus Pantoea, was the most promising bacterium because it increases peanut plant biomass in inoculation experiments. Peanut soils in the province of Cordoba harbor bacteria with major plant growth promotion properties which represent a potential source of new strains that could be used as biological inoculants in agriculture.