Inoculation with Bradyrhizobium japonicum enhances the organic and fatty acids content of soybean (Glycine max (L.) Merrill) seeds

Soybean (Glycine max (L.) Merrill) is one of the most important food crops for human and animal consumption, providing oil and protein at relatively low cost. The least expensive source of nitrogen for soybean is the biological fixation of atmospheric nitrogen by the symbiotic association with soil bacteria, belonging mainly to the genus Bradyrhizobium. This study was conducted to assess the effect of the inoculation of G. max with Bradyrhizobium japonicum on the metabolite profile and antioxidant potential of its seeds. Phenolic compounds, sterols, triterpenes, organic acids, fatty acids and volatiles profiles were characterised by different chromatographic techniques. The antioxidant activity was evaluated against DPPH, superoxide and nitric oxide radicals. Inoculation with B. japonicum induced changes in the profiles of primary and secondary metabolites of G. max seeds, without affecting their antioxidant capacity. The increase of organic and fatty acids and volatiles suggest a positive effect of the inoculation process. These findings indicate that the inoculation with nodulating B. japonicum is a beneficial agricultural practice, increasing the content of bioactive metabolites in G. max seeds owing to the establishment of symbiosis between plant and microorganism, with direct effects on seed quality.