Suppression of nodulation in soybeans by superoptimal inoculation with Bradyrhizobium japonicum

Symbiotic nodulation of the primary roots of soybeans (Glycine max L. Merrill cv. Pride 216) is regulated by the plant, and is suppressed in response to a high inoculum dose of Bradyrhizobium japonicum USDA strain I–110 (ARS)+ applied at one time to the root. If an optimal dose is followed 10 h later by a superoptimal dose, nodules from the first inoculum near the base of the primary root are suppressed in a dose‐dependent way similar to that observed after single inoculations. The nodules which appear are probably derived from infections initiated by the bacteria in both inocula.