Isolation and Characterization of Plant Growth-Promoting Rhizobacteria from Organic Compost and Their Beneficial Effect on Oryza sativa L. cv. RD47

Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that enhance plant growth in the rhizosphere. This study aims to isolate and characterize PGPR for biofertilizer development. Sixteen bacterial strains were isolated from the organic compost at the On Nut organic composting plant in Bangkok, Thailand. These isolates including seventeen actinomycete isolates from laboratory culture collection were evaluated for plant growth-stimulating properties, such as indole-3-acetic acid production (IAA), ammonia production, phosphate solubility, and chitinase production. Isolates 10, 12, 15, and 18 exhibited PGP properties with highest phosphate solubility. Especially, isolate 12 demonstrated the production of IAA at 0.0478 μg/mL, gibberellin production (GA3) at 0.3193 μg/mL, phosphate solubility at 11.0119 μg/mL and exhibited the highest percent inhibition of radial growth (PIRG) against Colletotrichum gloeosporioides C1060. In pot experiments on rice (Oryza sativa L. cv. RD47) with isolate 12 for 10 days, it showed statistically significantly increased root dry weight (p ≤ 0.05) compared to the other treatments. 16S rRNA sequence analysis by EZBiocloud revealed that isolate 12 wasclosely related to Bacillus licheniformis. This bacterium exhibits the potential of biofertilizer for an early stage of Oryza sativa L. cv. RD47