Enhancing Cottonseed Oil Quality Using EPS-Producing Azotobacter chroococcum XH2018 Under Salt Stress

Makhammadjon Kosimov, Gulirukh. Bakhromova, Mohichehra Pattaeva and Bakhtiyor Rasulov

Background and Objective: Excess Na⁺ and Ca²⁺ cations in the soils of Uzbekistan are major limiting factors for crop production, creating significant abiotic stress for plants. Therefore, finding alternative strategies to enhance crop productivity is critical, especially given that over 80% of irrigated lands in Uzbekistan are salt-affected. The purpose of this study was to evaluate the potential of the diazotrophic strain Azotobacter chroococcum XH2018 and its exocellular biopolymers EPS and total soluble proteins for mitigating Na⁺/Ca²⁺ stress. Materials and Methods: The study involved laboratory assays to quantify Na⁺ and Ca²⁺ removal by bacterial EPS, followed by an experiment using saline soil. Cotton plants were grown under different treatments, including mineral NPK and bio-organic treatments. Agronomic traits such as boll number, fiber quality, seed weight and oil content were measured. Statistical analysis was conducted using ANOVA and Tukey’s post hoc test to determine significant differences among treatments at p<0.05. Results: The exopolysaccharide (EPS) and other extracellular biopolymers produced by Azotobacter chroococcum XH2018 were capable of solubilizing up to 155,031.1 mg/L of Ca²⁺ and removing 18,969.88 mg/L of Na⁺, thereby neutralizing their harmful effects on plants. In salt-affected soils, cotton boll weight increased by 12.65%, fiber weight and length increased by 10.83 and 0.38%, respectively, while the number and weight of seeds increased by 9.4% and 13.63%. Additionally, the oil content in cottonseed rose by 28.42%, with linoleic acid comprising 52.34% of the total, surpassing the 51.54% linoleic acid yield observed with mineral NPK fertilization. Conclusion: Azotobacter chroococcum XH2018 and its EPS effectively mitigated Na⁺/Ca²⁺ stress and significantly improved cotton growth, yield and seed oil quality in salt-affected soils.

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