Exploration, isolation and characterization of indigenous rhizobacteria from patchouli rhizosphere as PGPR candidates in producing IAA and solubilizing phosphate

Abstract Microorganisms that are active and aggressive colonizing the rhizosphere are known as rhizobacteria. They are able to act as biofertilizers, bioprotectants, biostimulants and bioremediation. This study aims to identify and characterize groups of rhizobacteria present in the patchouli rhizosphere that can produce IAA compounds and have the ability to solubilize phosphate in the soil. Soil samples were taken from the patchouli rhizosphere at Purwosari Village, Nagan Raya, Aceh Province, Indonesia. This study used quantitative and qualitative descriptive analysis through serial dilutions to obtain rhizobacterial strains. Parameters observed were macroscopic and microscopic characteristics, gram test, IAA production and phosphate solubilization. The study obtained 37 isolates of rhizobacteria from Purwosari (PS), comprising 25 isolates of gram positive and 12 isolates of gram negative. The rhizobacteria PS 5/1 produced the lowest IAA at 21.66 ppm, whereas isolate 5/6 C produced the highest IAA at 83.38 ppm. Twenty-five isolates of rhizobacteria could solubilize phosphate while the remaining 12 isolates did not have this ability. The rhizobacteria PS 7/1 resulted in the highest PSI at 2.55 and isolates PS 8/7 produced the lowest PSI at 1.33. The rhizobacteria isolates that can produce IAA and phosphate solubilizing have the potential to be used as PGPR candidates.