Isolation of Halotolerant Bacteria from Rhizosphere of Khewra Salt Mine Halophytes and Their Application to Induce Salt Tolerance in Wheat

Broad manipulation of halotolerant plant growth promoting bacteria (PGPB) is very important in agriculture. In the present research, survival and adaptability of PGPB was determined under saline conditions. From the rhizospheric soil of Justicia adhatoda, Chenopodium murale and Cenchrus ciliaris, growing in Khewra salt mine, 20 bacterial strains were isolated. Out of these, six strains were found to be highly salt tolerant and they were characterized on the basis of their morphology, biochemical traits and sequence analysis of 16S-rRNA gene. These strains were identified as Bacillus megaterium, Bacillus tequilensis, Bacillus xiamenensis, Pseudomonas putida, Pseudomonas aeruginosa and Staphylococcus pasteuri. On the basis of plant growth promoting activities and extracellular enzyme secretions, B. megaterium, B. tequilensis and P. putida were selected and used for further analyses. All selected PGPRs showed antibiotics tolerance and the maximum tolerance was exhibited by B. tequilensis. Moreover, all the selected bacterial strains produced various phytohormones including indole-3-acetic acid (IAA), gibberellic acid (GA3) and abscisic acid (ABA). These strains enhanced root length, shoot length and leaf area of wheat seedlings by increasing the uptake of macronutrients (nitrogen, phosphorus and potassium). On the basis of these findings, these PGPRs can be considered as potential bio-inoculants to mitigate salt tolerance.