Isolation and Molecular Characterization of Potential Plant Growth-Promoting Bacteria from Groundnut and Maize

Abstract

Exploring microbial resources from coastal environments is crucial for enhancing food security; however, current knowledge remains limited. This study aimed to isolate and molecularly characterize bacteria associated with maize and groundnut, and to evaluate their potential as plant growth-promoting (PGP) agents. Rhizobacteria were isolated from rhizospheric soil, and endophytic bacteria were obtained from surface-sterilized and macerated plant roots. One gram of each sample was suspended in sterile distilled water in test tubes, serially diluted, and plated on nutrient agar. After incubation, distinct colonies were sub-cultured to obtain pure cultures for biochemical tests, screening for PGP traits, assessment of pH and salt tolerance, optimal growth conditions, bioinoculation potential, and molecular analysis. Out of sixty isolated bacteria, five potent strains, BS1-BS5, were identified. BS3 showed the highest mannanase activity, with a 2.3 cm zone of clearance, while BS2 exhibited high indole-3-acetic acid (IAA) and phosphate solubilization activities of 10.92 µg/mL and 10.78 mg/L. BS1 and BS4 demonstrated high drought tolerance, 0.94 and 0.98 at 10% PEG, with BS1 also showing maximum salt tolerance of 0.76. At 6.0 g and 2.0 g supplementation, BS1 and BS2 utilized 100% lactose and fructose. BS3 exhibited the highest percentage of antifungal activity, with a 30.12% inhibition rate. BS4 and BS5 promoted shoot lengths of 55.00 cm and 49.80 cm, respectively. Although the bacterial species isolated are generally considered pathogenic, their positive effects contributed significantly to maize growth.