PLANT GROWTH IMPROVEMENT THROUGH BIOINOCULATION OF IDENTIFIED RHIZOBACTERIA FROM MAIZE RHIZOSPHERE

This study aimed to isolate and characterize bacteria from maize rhizosphere soil with potential plant growth-promoting (PGP) properties. Soil samples were analyzed using serial dilution, pour plating, and streak plating to obtain pure bacterial cultures. The isolates underwent biochemical tests, PGP screening, process optimization, molecular identification, and maize seed bioinoculation trials. Morphological analysis showed flat colony elevation in all isolates except A2. A1 and A2 had rough textures, while A3 was smooth. All isolates were rod-shaped, occurred in chains, fermented sugars, and tested positive for PGP traits. Isolate A1 showed the highest nitrogen fixation zone of 2.0 cm. Quantitative analysis revealed that A2 exhibited nitrogen fixation and zinc solubilization activities of 2.93 and 2.34 µg/mL, respectively. A1 produced 2.68 µg/mL of indole-3-acetic acid (IAA). Both A1 and A2 exhibited enzymatic activity, with A1 recording a high amylase activity of 6.50 U/mL. Isolate A2 responded well to 2 g fructose with highest value 2.24, while A3 showed 2.23 in 1 g potassium nitrate-supplemented medium. All isolates grew in lead-supplemented media, with no inhibitory effects from other metals. Maximum IAA production of 2.83 µg/mL was recorded in medium with 8 g sucrose. Molecular identification confirmed the bacterium as Vagococcus fluvialis. The isolates were resistant to Ampiclox, Zinnacef, and Amoxicillin. Bioinoculated maize seeds showed improved growth in maize length 2.1 cm (in vitro), 73.3 cm (field), and 52.0 cm (greenhouse), compared to un-inoculated. These findings support the potential use of Vagococcus fluvialis as a bioinoculant to enhance maize growth through multiple PGP mechanisms.