Nodulation competitiveness in the Rhizobium-legume symbiosis.

Successful nodulation of legumes by rhizobia is a complex process that, in the open field, depends on many different environmental factors. Generally, legume productivity in an agricultural field may be improved by inoculation with selected highly effective N2-fixing root nodule bacteria. However, field legume inoculation with Rhizobium and Bradyrhizobium spp. has often been unsuccessful because of the presence in the soil of native strains that compete with the introduced strain in nodule formation on the host plants. This ability to dominate nodulation is termed 'competitiveness' and is critical for the successful use of inoculants.