CHARACTERIZATION OF SOME NONFIXING MUTANTS OF COMMON BEAN (PHASEOLUS-VULGARIS L)

With 18 strains of Rhizobium leguminosarum bv. phaseoli the bean mutants R99 and NOD 125 remained essentially non-nodulating, while the mutant R69 produced a variable number of small white ineffective nodules, and the wild-type parent-line OAC Rico formed a variable number of pink effective nodules. Both R69 and R99 grew less vigorously than OAC Rico, but possessed similar levels of nitrate reductase in both roots and leaves, and responded in a normal way to increased supply of combined nitrogen. Reciprocal grafts between the non-nodulating R99 and NOD125, the ineffective R69, the wild-type parent line OAC Rico, and the supernodulating R32BS, demonstrated that the non-nodulating and ineffective characters were controlled by the root, and confirmed that the supernodulation character was controlled by the shoot.