Enhancement of Phosphate Solubilization by Endophytic Bacteria Under Salinity and Phosphorus Deficiency Stress Conditions
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1
Samarkand State University named after Sharof Rashidov, University Boulevard 15, 140104, Samarkand, Uzbekistan
2
Kimyo International University in Tashkent Samarkand branch, 63 H.Abdullaev str, Samarkand, 140103, Uzbekistan
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Samarkand State Pedagogical Institute, Spitamin 161, Samarkand 140102, Uzbekistan
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Samarkand State Veterinary Medicine, Animal Husbandry and Biotechnology University, Mirzo Ulugbek-77, Samarkand 140100, Uzbekistan
5
Samarkand State Medical University, Samarkand 140100, Uzbekistan
Corresponding author
Shahzod Axanbayev
Samarkand State University named after Sharof Rashidov, University Boulevard 15, 140104, Samarkand, Uzbekistan
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ABSTRACT
Soil salinization and phosphorus (P) deficiency are critical environmental challenges that severely limit global agricultural productivity, particularly in the arid regions of Uzbekistan. Under saline conditions, P is rapidly immobilized, becoming unavailable for plant uptake, which leads to stunted growth and significant yield losses. This study addresses the urgent need for sustainable bio-remediation by evaluating halotolerant endophytic bacteria as effective bio-fertilizers. Several endophytic bacterial strains isolated from native halophytes were screened for their tolerance to extreme salinity (up to 10% NaCl) and their ability to solubilize insoluble phosphates. The most potent isolates, Pseudomonas putida KoPr129 and Bacillus amyloliquefaciens HAPH2, were biochemically characterized for plant growth-promoting (PGP) traits, including IAA, ammonia, and HCN production. A 6-week greenhouse pot experiment was conducted to validate their efficacy on wheat (Triticum aestivum L.) under 150 mM NaCl stress and P-deficient conditions. In vitro assays confirmed that P. putida KoPr129 maintained a robust phosphate solubilization index (FPI 18.16±0.56 mm) even at 10% NaCl. Greenhouse trials demonstrated that inoculation with these endophytes significantly mitigated the negative impacts of combined stress. Specifically, P. putida KoPr129 increased wheat shoot length by 69% and more than doubled the total phosphorus uptake (over 130% increase) compared to the non-inoculated stressed control. Biochemical profiling revealed high levels of IAA production (++) in both strains, facilitating enhanced root architecture and nutrient acquisition. Our findings demonstrate that halotolerant endophytes, particularly P. putida KoPr129, are superior candidates for the development of effective bio-inoculants. These results provide a promising pathway to restore soil fertility and improve wheat productivity in degraded, saline-alkali landscapes, offering a sustainable alternative to chemical fertilizers.