Bacteria consortium optimization improves nutrient uptake, nodulation, disease suppression and growth of the common bean (Phaseolus vulgaris) in both pot and field studies

Several plant growth promoting bacteria (PGPB) were isolated from the nodules and rhizosphere of common bean and evaluated for their potential to improve its growth and yield. Among these, 86% isolates produced IAA and siderophore whereas almost all (95%) were able to solubilize inorganic phosphate, only 4.54% isolates were able to produce ACC deaminase. Among all isolates three had superior growth promoting characteristics. These three were identified by 16S rRNA sequence homology as belonging to Bacillus sp., Pseudomonas sp., and Rhizobium leguminosarum. All three isolates strongly inhibited several plant pathogens in vitro. Efficiency of these three strain and their consortia was evaluated in pot assay as well as in a field study. In both pot and field studies the three strains, singly or in consortia, increased germination, plant height and weight and nodulation compared to controls. Our results show that consortia were more efficient at growth promotion and disease suppression than the strains applied individually. The number of pods per plant, seeds per pod, grain yield, stover yield, biological yield, and harvest index were increased the most in consortium-3, followed by consortium-2, consortium-1, then the bacteria used singly. Therefore, the utilization of the bacterial consortium comprised of strains RPN5, BPR7 and PPR8 could be beneficial to maximize growth and grain yield of crop in field.