Short-Term Evolution of Rhizobial Strains Toward Sustainability in Agriculture

Abstract

Some rhizobial strains are widely used as biofertilizers substituting inorganic nitrogen fertilization, mainly for legumes. The successful use of rhizobia in agriculture derives from appropriate selection of strains with high capacities to fix nitrogen. However, the selection of more efficient rhizobia is from a limited number of plant growth conditions. In other environments, inoculant strains may exhibit low competitiveness or low nitrogen fixation. We argue here that rhizobial strains are continuously evolving in plants and therefore recommend an approach inspired on experimental evolution studies where strains adapted to particular conditions may be selected. The selection and detection of efficient rhizobial strains should take place under local field conditions in order to obtain superior nitrogen-fixing symbionts. To support our recommendation, we reviewed different examples of experimental evolution in bacteria and summarized results on rhizobial co-inoculation with different microbes.