Soil salinity poses a global threat to world agriculture by reducing the yield of crops and ultimately the crop productivity in the salt affected areas. Soil inoculation of salt tolerant Plant Growth Promoting Bacteria (ST-PGPB) i.e. free living diazotrophs and phosphate solubilizers not only help in achieving food security but also results in fortifying macro and micro nutrients for mankind and quality of soil organic nutrients, improvement of agro-ecosystem with minimum pollution hazards. Three salt tolerant native PGPB were isolated from Vaso farm and screened based on their abilities to fix N and solubilize P. Isolates AAU V2 and AAU V8 were found N-fixer while, AAU V1 was found P-solubilizer based on their growth characteristics on selective media. The salt tolerance (i.e. NaCl and KCl) test showed that all three isolates were capable to grow at varied salt concentration i.e. from 4.5 to 8.5 % in vitro. A liquid assay test on survival and multiplication ability of chosen isolates indicated that all three isolates grows well in all tested growth medium except minimal salt broth without carbon source. ST-PGPB isolates were identified by 16S rRNA gene sequencing technique as Priesta (= Bacillus) AAU V1 nr. sp. flexia (NCBI ACC. No. OR287447), Cupriavidus AAU V2 nr. sp. alkaliphilus (NCBI ACC. No. OR287481) and Lysobacter AAU V8 nr. sp. yangpyeongensis (NCBI ACC. No. OR287436). The isolates were further tested for PGP traits and found that all three isolates were positive for the availability of macro nutrient (N, P and K). The highest nitrogen fixation (20.25 mg N g-1 of sucrose consumed) was recorded by Cupriavidus AAU V2, followed by Lysobacter AAU V8 (18.70 mg N g-1 of sucrose consumed) and Priestia AAU V1 (8.05 mg N g-1 of sucrose consumed). Maximum P solubilization zone was recorded for isolate Priestia AAU V1 (zone of 10.2 mm). All three isolates found moderate K solubilizer and good zinc solubilizer. Moreover, found to produce IAA and ACC deaminase enzyme. A liquid biofertilizer formulation, Bio NP consortium was prepared by mixing all three chosen isolates in equal proportions and further evaluated for its shelf life study up to one year. Shelf life study showed that survival of bacteria in consortium was found excellent up to 6 months and minimum count sustained as per FCO up to 1 year.

Plant growth promoting bacteria, PGP traits, Bio NP formulation, Salt tolerant, N fixation, P solubilization, Shelf-life

The present investigation was carried out to isolate and characterize native salt tolerant PGPB from low saline soil of Vaso farm. Three potential isolates were selected based on their morphological characters, salt tolerance abilities and abilities to fix atmospheric nitrogen and soliubilize phosphorous. Morphological and molecular characterization identified the native salt tolerant isolates as Priesta (= Bacillus) AAU V1 nr. sp. Flexia (NCBI Accession no. OR287447) as P solubilizer; Cupriavidus AAU V2 nr. sp. Alkaliphilus (OR287481) as free-living N-fixer and Lysobacter AAU V8 nr. sp. Yangpyeongensis (OR287436) as free-living N-fixer. Overall, PGP traits showed that for 5 key tests assessed for macronutrients the isolates found better and good for Zinc, ACC deaminase and IAA production. On the whole, ST-PGPB isolated from low saline soil of Vaso region exhibited good salt tolerance and best plant growth promoting traits in laboratory. The native Bio-NP bacterial liquid consortium product prepared was sustained well at ambient temperature in laboratory.

Saiyad M.M., Vyas R.V., Patel H.K. and Mevada K.D. (2023). Isolation, characterization and Formulation Development of Salt Tolerant Plant Growth Promoting Bacteria. Biological Forum – An International Journal, 15(12): 340-347.