Mitigation of salinity stress in plants using plant growth promoting bacteria

Salinity is one of the major constraints prevailing in environment that affects not only plant growth but also agriculture productivity and soil fertility. Salinity stress causes nutritional and hormonal imbalance, ion toxicity, oxidative and osmotic stress and increased susceptibility of plant to diseases. Increasing use of chemical based fertilizers creates demand for environmental friendly and ecological compatible alternative in agriculture. Plant growth promoting bacteria (PGPB) have tremendous ability to mitigate salinity stress and ameliorate plant growth, playing vital role in food security by increasing agriculture crop productivity. PGPB inoculation under salinity promotes plant growth by several traits including 1-aminocyclopropane 1 carboxylate (ACC) deaminase activity, synthesis of plant hormones (such as indole acetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA), cytokinin) and exopolysaccharides. PGPB alleviates salinity stress in plants by providing nutrients, maintaining high potassium and sodium ratio, increasing accumulation of osmolytes, enhanced photosynthesis and activity of antioxidant enzymes. The present review highlights and discusses current knowledge on effect of salinity stress on plant growth, PGPB mechanisms resulting in mitigation of salinity stress and increasing plant growth. It assesses morphological, biochemical, physiological and molecular changes induced in plants suffering from salinity when supplemented with PGPB.