The Co-inoculation of Rhizobium and Bradyrhizobium Increases the Early Nodulation and Development of Common Beans

Abstract

It has recently been shown that the co-inoculation of Rhizobium tropici and Bradyrhizobium spp. can benefit the nodulation, development, and biological nitrogen fixation of common beans (Phaseolus vulgaris L.). Here, we compared this type of co-inoculation with the co-inoculation of Azospirillum brasilense on two common bean cultivars and evaluated whether they can stimulate the early nodulation of this crop, aiming at anticipating the contribution of biological nitrogen fixation to plant nutrition. The co-inoculation with B. elkanii 29w increased the number of nodules in the V3 and V4 stages. Both co-inoculations stimulated a larger mass of nodules and larger shoot biomass during the V4 stage. The co-inoculation of Bradyrhizobium also stimulated root growth. The co-inoculation effects were consistent for the two tested cultivars, but some differences in response indicate a possible genotype effect. We can conclude that the co-inoculation of B. elkanii benefits the common bean during the early stages of its cycle. These effects are comparable with the effects of the co-inoculation with Azospirillum brasilense Sp 245.