Isolation and characterization of plant growth-promoting rhizobacteria from rhizospheric soil of hill paddy

Plant growth-promoting rhizobacteria (PGPR) enhance plant growth through mechanisms such as nutrient solubilization, nitrogen fixation, phytohormone production, and pathogen suppression, yet species from uncommon environments like hill paddy rhizospheric soil remain underexplored. This study aimed to isolate and identify PGPR from hill paddy rhizospheric soil, assess their plant growth-promoting traits, and evaluate their effects on plant growth. Soil samples were processed to isolate rhizobacteria, which were screened for nutrient-solubilizing and nitrogen-fixing abilities, and tested for antifungal activity against Fusarium solani . Selected strains were evaluated using mustard ( Brassica juncea ) as a model plant, and the most promising isolate was identified via 16S rRNA gene sequencing. Eight isolates demonstrated nitrogen fixation and phosphate and potassium solubilization, with one strain, RRZ034, showing consistently higher mean plant growth values, a high phosphate solubilization index (3.42 ± 0.08), and positive antifungal activity. Molecular analysis identified RRZ034 as Pseudomonas nicosulfuronedens , a species with limited previous documentation. These findings highlight the potential of P. nicosulfuronedens RRZ034 as a nutrient-solubilizing and pathogen-suppressing PGPR for future application in sustainable agriculture.