The Molecular Genetics of Nodulation Competitiveness in Rhizobium and Bradyrhizobium. Eric W. Triplett. Department of Agronomy and the Center for the Study of Nitrogen Fixation, University of Wisconsin, Madison 53706-1597 U.S.A. . MPMI 3:199-206. Accepted 8 March 1990. Copyright 1990 The American Phytopathological Society.