GENETIC-VARIABILITY OF NODULATION COMPETI TIVENESS IN NODULE BACTERIAAND ITS USE IN SELECTION

Results of a study of natural and mutational variability in nodule bac teria (Rhizobium and Bradyrhizobium) with regard to their competitive nodulation ability in leguminous plants are reviewed. Direct and indir ect methods of testing nodulation competitiveness, which allow selecti on of rhizobial mutants with alterations in this trait, are considered . Correlations of competitiveness with various cultural and biochemica l properties, such as auxotrophy, antibiotic resistance, motility, syn thesis of polysaccharides, and symbiotic traits (nodulating ability, n itrogen-fixing ability, and efficiency) are discussed, using native rh izobial strains and their mutants as an example. Possible ways of sele cting effective strains of nodule bacteria om improved nodulation comp etitiveness are considered.