Polymeric formulations of liquid inoculants with rhizobia exopolysaccharides increase the survival and symbiotic efficiency of elite Bradyrhizobium strains.

We studied the survival of four elite strains of Bradyrhizobium in liquid inoculants with three formulations with exopolysaccharides extracted from other rhizobia genera, and the symbiotic efficiency of these elite strains with soybean and cowpea in a greenhouse. For that purpose, we verified the effectiveness of formulations for maintaining the cell viability of strains by counting the colony-forming units (CFU) per milliliter of the liquid inoculants with formulations after 90 days. For survival of the soybean inoculant strains, 29W and CPAC15, the largest number of CFU (> 10 10  mL -1 ) after 90 days was observed in the PEPS formulation. For the cowpea inoculant strains, INPA3-11B and UFLA3-84, the REPS 1 formulation had the largest number of CFU (> 10 10  mL -1 ) after 90 days. The symbiotic efficiency of the PEPS formulation, followed by REPS 2 , was higher than that shown by the commercial inoculant in soybean. For cowpea, the three formulations with EPS, especially REPS 1 , showed symbiotic efficiency better than that of the commercial inoculant.