Evaluation of different Bradyrhizobium sp strains on nityrogen fixation capacity in two forage legumes

Nineteen avaiable strains of Bradyrhizobium sp were used to test two forage legumes, Crotalaria juncea(Crotalaria) and Cajanus cajans (Guandu) for symbiotic N-fixation ability. Greenhouse experiments were conducted for nine weeks in order to evaluate shoot, root, and nodule dry weight, nodule number, and shoot nitrogen content. Nine strains presented relative nitrogen efficiency (RNE) over 100 per cent with Crotalaria cultivar, whereas only 3 strains were more efficient with Guandu. Strain 633 was the only which presented a high yield with both cultivars. Finally, plant dry weight accumulation followed N accumulation obtaining 0.6757 correlation coefficient for Crotalaria and Guandu, respectively