Failure of inoculant rhizobia to overcome the dominance of indigenous strains for nodule formation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Documentation of the problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 13 Distribution of B,~~cly~~l i i~oDi~~rri groups in the United States . . . . . . . . . . . . . . . . . . . . . . . . . 5 13 Effects of bacterial and plant genotype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 14 Soil properties and levels of indigenous bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 15 Other factors in the field environment that may affect survival and (or) infection . . . . . . . . . . . . . . 5 15 Approaches to controlling infection in the field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 16 Use of high inoculant doses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 16 Use of bacteriocidal agents in conjunction with resistant strains . . . . . . . . . . . . . . . . . . . . . . . 5 16 Inoculant formulation or placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 16 Modification or selection of host genotype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 16 Modification or selection of bacterial genotype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 17 Potential problems confronting researchers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 17 Genetic diversity of rhizobial soil residents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 17 Prediction of field dominance by studies of competitiveness . . . . . . . . . . . . . . . . . . . . . . . . 5 17 Antibiotic-resistant ibolates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 18 Sampling of field populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 18 Summary and prospects for the future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 18 Key worcls: competitiveness, nitrogen fixation, rhizobial ecology, Blncl~rliizobi~~rri.