A critical process in the leguminous crops cycles is biological nitrogen fixation (BNF). Application of inoculants with N fixing bacteria is economically and environmentally favourable. The aim of this work was to select competitive native peanut microsymbionts, evaluate their survival in inoculant support and assess their impact on peanut ( Arachis hypogaea
L.) production under field conditions at Córdoba province in Argentina. The efficient N fixing Bradyrhizobium
sp. J-81 and Bradyrhizobium
sp. J-237, previously obtained from peanut nodules in the region of Cordoba, Argentina, were evaluated. In microcosm assays, plants inoculated with these isolates demonstrated better symbiotic parameters than those inoculated with reference strains. Different bacterial growth media and inoculant stabiliser solutions were evaluated. Balanced medium and arabic gum stabilising solution had optimal bacterial growth and the highest bacterial concentration and viability, respectively. Inoculation with either inoculants resulted in 44% greater peanut pod yield at Pizarro compared to the non-inoculated plants, although no significant differences were found with respect to commercial inoculants treatments.