Journal of Agronomy and Field Innovations

Background: Biological nitrogen fixation (BNF) by root-associated diazotrophs offers a sustainable alternative to synthetic nitrogen fertilizers in sugarcane, a crop with high nitrogen demand and substantial environmental footprint from conventional fertilization.
Objective: This study aimed to isolate, identify, and functionally characterize diazotrophic bacteria colonizing the rhizosphere and root endosphere of sugarcane, and to evaluate their plant growth-promoting potential.
Methods: Root and rhizosphere samples were collected from three sugarcane varieties across two agro-climatic zones. Diazotrophs were isolated on nitrogen-free semi-solid media (NFb, LGI, JNFb), characterized morphologically and biochemically, identified via 16S rRNA and nifH gene sequencing, and screened for nitrogenase activity (acetylene reduction assay), IAA production, phosphate solubilization, siderophore production, ACC deaminase activity, and biofilm formation. Data were analyzed using one-way ANOVA with Tukey's post-hoc test (p < 0.05).
Results: Forty-two isolates were recovered, clustering into six genera dominated by Gluconacetobacter, Herbaspirillum, and Azospirillum. Endophytic isolates showed significantly higher nitrogenase activity and IAA production than rhizospheric isolates, while phosphate solubilization and siderophore production were more prevalent among rhizospheric strains.
Conclusion: Sugarcane roots harbor a functionally diverse diazotrophic community with strong biofertilizer potential; endophytic strains in particular merit further field-scale evaluation for reducing chemical nitrogen inputs in sugarcane cultivation.