Effect of Competitiveness on Nodulation and Nitrogen Fixation in Common Bean (Phaseolus vulgaris L.)

The competition on the nodules formation on roots of a determinate growth bean (Phaseolus vulgaris L. variety: white Coco), between inefficient BIAT strain, and efficient foreign F11 strain of Polish origin, was studied in Culture chamber on sterilized sand.The nodules from the mixed inoculum of equal concentrations were identified using streptomycin antibiotic. Based on the number of nodules formed by each of the two strains inoculated separately; no relationship between efficacy and infectivity.In mixed inoculum, competitiveness for nodulation was influenced by strain efficiency, since strain F11 formed more nodules, producing 67.7% of flowering nodules.According to nodulation kinetics, this competitiveness in favor of the most efficient strain definitively, as of the twentieth days after the inoculation. The results of the dry matter yield and the fixed nitrogen amounts of the aerial organs of the three treatments clearly showed that the fixation efficiency of the F_11 strain; was severely affected by the presence of the inefficient strain.The competition capacity of efficient strains to colonize the nodulation sites and atmospheric nitrogen fixation capacity in the presence of another inefficient strain; are two independent parameters.