Colonization of Vigna radiata by a halotolerant bacterium Kosakonia sacchari improves the ionic balance, stressor metabolites, antioxidant status and yield under NaCl stress

Salinity stress is a major limiting factor that adversely affects the crop productivity. Considering these problems, present investigation was aimed to isolate and characterize a halotolerant PGPR strain to circumvent these problems. Strain MSK1 tolerated exceptionally 1000 mM of NaCl and identified as K. sacchari using 16S rRNA sequence analysis (accession number MG028651). Strain MSK1 was found metabolically active, producing substantial amount of growth regulating substances such as indole-3-acetic acid, ACC deaminase, siderophore, ammonia and hydrogen cyanide which, however, increased with increasing NaCl concentrations. Vigna radiata was used as test crop to evaluate the effect of NaCl as well as remediating potential of halotolerant K. sacchari. Phytotoxicity of salt to V. radiata plants was obvious under both in vitro and in vivo environments and increased in a dose related manner. Among the concentrations, the higher NaCl level (400 mM) exhibited more pronounced detrimental effect and significantly (P <= 0.05) decreased the germination attributes, dry biomass, photosynthetic pigments, symbiotic features and seed yield of V. radiata. However, antioxidant enzymes, proline, MDA, membrane damage, H2O2 content, relative leaf water content (RLWC) and Na+/K+ ion concentrations were increased with increasing NaCl concentrations. Contrarily, following soil inoculation, halotolerant K. sacchari MSK1 alleviated the salinity stress and improved the plant performance and augmented the dry biomass, chlorophyll formation, symbiosis and yield of V. radiate even in salt stressed condition. Besides these, strain MSK1 reduced the level of proline, MDA, H2O2 and antioxidant enzyme activity. Additionally, RLWC, membrane injury and Na+/K+ ions were reduced following the application of K. sacchari. The root colonization efficiency of K. sacchari even under salinity stress was examined by scanning electron microscopy. Conclusively, it can surely be suggested that halotolerant MSK1 strain could inexpensively be explored as best choice for augmenting the V. radiata production under salinity stressed soils.