Nodulation in peanut (Arachis hypogaea L.) roots in the presence of native and inoculated rhizobia strains

There is considerable interest in improving nitrogen ®xation in legumes to increase soil fertility, particularly in the developing countries. The effect of inoculation of peanut (Arachis hypogaea L.) seed with Bradyrhizobium sp. USDA 3187 was examined under ®eld conditions. In order to determine nodule occupancy, bacterial cells from surface-sterilized nodules of inoculated plants were isolated and characterized by their intrinsic antibiotic resistance and by agglutination test. Results obtained revealed that peanut roots were nodulated by native strain rather than the introduced one, indicating that strain USDA 3187 was not as competitive as naturalized peanut rhizobia. Data also showed that there were no signi®cant differences in nodule dry weight, plant dry biomass, nitrogenase activity and seed yield between uninoculated and inoculated treatments. # 1999 Elsevier Science B.V. All rights reserved.