Polymeric Formulations of Liquid Inoculants with Rhizobia Exopolysaccharides Increase Survival and Symbiotic Efficiency of Bradyrhizobium Strains with Cowpea and Soybean

Abstract We studied the survival of four elite strains of Bradyrhizobium in liquid inoculants with three formulations with EPS extracted from other rhizobia genera, and their symbiotic efficiency, with soybean and cowpea, in a greenhouse. For this purpose, we verified the utility of formulations for maintaining the cell viability of strains by counting the colony forming units (CFU) per milliliter of the liquid inoculants with formulations over 90 days. Survival of the soybean inoculant strains, 29W and CPAC15, in the PEPS formulation had the largest number of CFU (> 1010 mL− 1) after 90 days. For the cowpea inoculant strains, INPA3-1B and UFLA3-84, the formulations REPS1 had the largest number of CFU (> 1010 mL− 1) after 90 days. Symbiotic efficiency in soybean of the formulations PEPS and REPS2 was higher than that shown by the commercial inoculant. For cowpea, the three formulations with EPS showed symbiotic efficiency bigger than that of the commercial inoculant.