Effectiveness of exopolysaccharides and biofilm forming plant growth promoting rhizobacteria on salinity tolerance of faba bean (Vicia faba L.)

Abstract

This study aimed to investigate the production of biofilm and exopolysaccharides by plant growth promoting rhizobacteria (PGPR) under different salt concentrations. In this study, the activity of biofilm formation and exopolysaccharides production by 20 strains of PGPR which previously isolated and identified from root samples of different crops were determined under different salt concentrations. Out of 20 strains, only 12 PGPR strains have the ability to form biofilm at 0.0, 50, 100 and 150 mM NaCl concentration. PGPR strains with the highest activity of biofilm formation and exopolysaccharides production were selected to check them on the faba bean plants under different concentration of salt stress. Inoculation with PGPR strains increased plant growth at higher level of salt concentrations compared with their corresponding uninoculated ones. The strain Pseudomonas anguilliseptica SAW 24 showed the highest activity of biofilm formation and exopolysaccharides production at different NaCl concentrations furthermore, gave the highest records of plant height (cm), fresh and dry weight (g/plant) of faba bean plants. The activities of biofilm formation and exopolysaccharides production of plant growth promoting bacteria enhance faba bean plants against different salt concentrations. Key words: Biofilm, faba bean, exopolysaccharides, salinity, plant growth promoting rhizobacteria (PGPR).