Isolation and Characterization of Native Azospirillum and Phosphorus Solubilizing Bacteria from Finger Millet Rhizosphere

Abstract

Background: Finger millet is an important staple crop in different semi-arid and tropical regions of the world. In order to enhance finger millet yields and promote soil fertility, it is crucial to combine chemical fertilizers with biofertilizers such as Azospirillum, Azotobacter, and bacteria that solubilize phosphorus and potash in soil. Aim: This study aims to characterize the Azospirillum and Phosphate-solubilizing bacteria (PSB) isolates from finger millet soil. Methodology: A total of nineteen rhizospheric soil samples of finger millet were collected from villages in the Radhanagari, Karveer, Shahuwadi, and Panhala tehsils of Kolhapur district, Maharashtra, India. The samples were brought to the laboratory for the isolation of Azospirillum and phosphorus-solubilizing bacteria. Isolation was carried out on Nfb and Pikovskaya’s medium for Azospirillum and PSB, respectively. Six isolates of Azospirillum and three isolates of PSB were obtained from these samples. Results: Most of the Azospirillum isolates showed variability in cell morphology, i.e., rod and vibroid. Colonies of Azospirillum on semi-solid NFb medium showed a white sub-surface pellicle. In the biochemical analysis, all the isolates showed positive results for the catalase test and KOH test. Most of the PSB isolates showed variability in colony shape, i.e., circular and irregular. All three PSB isolates showed a smooth colony surface. In the biochemical analysis, all the isolates showed positive results for the methyl red test. Conclusion: Significant morphological and biochemical diversity was found when Azospirillum and phosphate-solubilizing bacteria (PSB) isolates from finger millet soil were characterized. In terms of biochemistry, every PSB isolate tested positive in the methyl red test, indicating the possibility of acid generation. These results advance our knowledge of the microbial diversity in the rhizosphere of finger millet and could guide the creation of biofertilizers in the future.