Isolation and characterization of plant growth promoting rhizobacteria associated with medicinal plant Picrorhiza Kurroa

Plant growth promoting rhizobacteria (PGPR) are naturally occurring soil bacteria that aggressively colonize plant roots and benefit plants by several mechanisms like IAA production, siderophore production, phosphate solubilization, etc. Phosphate solubilizing microorganisms play an important role in supplementing phosphorus to the plants by several mechanisms like lowering of pH by acid production and ion chelation and thus benefit plant growth and development. Therefore, the aim of this study was to determine the phosphate solubilizing potential of plant growth promoting rhizobacteria (PGPR) isolated from Picrorhiza kurroa. Forty bacterial isolates were selected (by modified replica plating technique) as the representative of the total plated population from the rhizosphere soil and rhizome/roots of the Picrorhiza kurroa from two locations of Chamba district. All the bacterial isolates were able to grow simultaneously on nutrient agar, Pikovskaya’s, nitrogen free media and CAS media and selected for further screening for various plant growth promoting activities. Four phosphate solubilizing bacterial isolates exhibited very good production of chitinase enzyme with a zone size of 30-45mm.Maximum IAA production of 30.00µg/ml was exhibited by PkR(34)* and PkR(7b)*. The isolate Pk12(b) produced maximum per cent siderophore unit ( 27.21%). After screening, five isolates (PkR(7a)*,Pk7(B),Pk14(b), Pk12(d) and PC4) were selected for their ability to solubilize tricalcium phosphate(TCP). Out of the five isolates, isolate PkR(7a)* showed maximum P- solubilization of 320.00 mg/l at after 72 h of incubation at 35 0C in PVK broth. The isolate PkR(7a)* was identified to be Bacillus subtilis according to sequence analysis of 16S rDNA.