Effectiveness of different Ensifer meliloti strain-alfalfa cultivar combinations and their influence on nodulation of native rhizobia

The impact of inoculation on plant growth and on nodulation of native rhizobia was analyzed using combinations of five Ensifer meliloti strains and three alfalfa cultivars. The strains CCBAU01199 and CCBAU01290 showed a broad host-spectrum, improving the growth and nitrogen fixation in all three alfalfa cultivars (32–156%), with nodule occupation 22–54%. The diversity of native rhizobia in the alfalfa nodules may be reduced or increased by inoculation, depending on both the cultivar and the strain. These results confirmed a preference between the rhizobial strains and the plant cultivars, and revealed that the inoculants and native rhizobia competed for occupancy of nodules and cooperated to enhance the nodule numbers.