Several genetic factors have been identified which govern specific nodulation response in soybeans. The RJ2 genotype, carried by the cultivars 'Hardee' and 'CNS,' conditions an ineffective response in specific combination with Rhizobium japonicum strains of serogroups c1 and 122. The ineffective response is characterized as the development of either cortical proliferations on the roots or rudimentary nodules, rather than normal nodules.