Isolation and Characterization of Plant Growth-Promoting Rhizobacteria Associated with Sesbania sesban (L.) Merr. in Tan Hung commune, Tay Ninh Province, Vietnam

This study aimed to isolate and characterizes indigenous plant growth-promoting rhizobacteria (PGPR) associated with Sesbania sesban (L.) Merr. in Tan Hung commune, Tay Ninh province, Vietnam. Twenty bacterial isolates were obtained from rhizosphere soil and quantitatively screened for key functional traits, including biological nitrogen fixation, phosphate and potassium solubilization, and indole-3-acetic acid (IAA) production. Morphological analysis revealed a diverse bacterial community, dominated by rod-shaped (70%) and Gram-positive (55%) isolates. All isolates demonstrated nitrogen-fixing and phosphate-solubilizing capabilities, although their efficiencies varied significantly. Strains DD04 and DD11 exhibited the highest nitrogen fixation capacity (1.66 mg/L NH4+). For phosphate solubilization, DD19 showed the highest average value (119.01 mg/L P₂O₅), while DD09 reached the maximum concentration (172.66 mg/L) after 20 days. Additionally, DD10 and DD20 were the most efficient IAA producers, with peak concentrations of 3.95 mg/L and 4.02 mg/L, respectively. Potassium solubilization was observed in 30% of the isolates, with DD13 showing the highest efficiency (1.41). These findings highlight the potential of S. sesban rhizosphere as a reservoir of beneficial bacteria, with several elite strains representing promising candidates for sustainable biofertilizer development in Vietnam.