Characterization of plant growth-promoting Rhizobacteria from Cowpea Rhizosphere

Abstract

The increasing demand for sustainable agricultural production has intensified efforts to identify environmentally friendly alternatives to synthetic fertilizers. This study investigated the isolation and characterization of plant growth-promoting rhizobacteria (PGPR) from the rhizosphere of cowpea (Vigna unguiculata (L.) Walp) with the objective of evaluating their potential to enhance plant growth and physiological performance. Rhizosphere soil samples were collected, and bacterial isolates were obtained and characterized using standard morphological and biochemical procedures including gram staining, indole test, catalase test etc. The isolates were screened for key plant growth-promoting traits, including HCN production, phosphate solubilization, and Ammonia production. The finding of the study shows that soil chemical properties varied significantly among the samples. Sample C had the highest organic carbon (1.397 ± 0.06ᵃ %) and nitrogen (0.150 ± 0.02ᵃ %), significantly higher than all other samples, indicating richer soil fertility. Also the Week 3 group exhibited the highest mean AL (20.00 ± 2.61 cm) and was statistically comparable to the Week 4 (18.42 ± 1.43 cm) and Control (18.00 ± 1.00 cm) groups, as indicated by the shared superscript a and b. The biochemical characterization reveals that all isolates were Gram-positive and uniformly methyl red (MR) positive indicating a consistent ability to produce stable acid end-products from glucose fermentation. The study concludes that cowpea rhizosphere soil harbors diverse bacterial isolates with promising plant-growth-promoting characteristics and potential for use in sustainable agricultural production. Further field-based studies are recommended to validate their effectiveness.