Plant growth promoting rhizobacteria are of great interest in sustainable agriculture and have gained much attention in recent years. Yet, these bacteria often failed to perform their functions in the plants due to poor colonization in the rhizosphere. There are no vibrant procedures available to identify the traits responsible for the effective colonization of these PGPR strains under in vitro conditions. In the present work, twenty low molecular weight carbon compounds predominantly present in the root exudates were used to assess the differential carbon substrate utilizing profile of the PGPR strains. Further, the synthetic root exudate solution which mimics the rhizo-deposits comprising of sugars, organic acids and amino acids in a ratio of 60:35:5 % were used to assess the growth and biofilm production under in vitro condition. The results revealed that these two assays can clearly discriminate the high and low competitive strains of PGPR. Among the twelve strains, Aeromonas hydrophila QS7-4, Enterobacter sp. QS20- 11 and Klebsiella pneumoniae QS24-6 were identified as the strains with high colonizing ability. Hence, developing inoculant with these traits are essential for effective colonization and for exceling maximum benefit for the agricultural productivity.
Key words : Biofilm, plant growth promoting rhizobacteria, differential carbon utilization.