Biocontrol Potential of Kosakonia cowanii Strain TKS G-1 against Wheat Stripe Rust caused by Puccinia striiformis f. sp. tritici

Background Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici ( Pst ), poses a significant threat to global wheat production. Results This study aimed to evaluate the biocontrol potential of endophytic bacteria against this devastating disease. Strain TKS G-1, isolated from healthy wheat roots, was identified as Kosakonia cowanii through polyphasic taxonomy (morphological, physiological, and phylogenetic analysis of 16S rDNA and rpo B sequences). The (fermented liquid with bacterial cells) FLBC of TKS G-1 inhibited Pst urediospore germination by 88.89% in vitro. In pot tests, treatment with FLBC of TKS G-1 achieved 64.95% disease control efficacy, while significantly promoting plant height, fresh weight, and dry weight compared to the pathogen-only control. Further analyses revealed that the antifungal activity was primarily mediated by extracellular secondary metabolites distinct from volatile organic compounds. Additionally, strain TKS G-1 exhibited multiple plant growth-promoting (PGP) traits, including indole-3-acetic acid (IAA) production, siderophore secretion, amylase and ACC deaminase activity, inorganic phosphate solubilization, and atmospheric nitrogen fixation. Conclusions These results collectively demonstrated that Kosakonia cowanii TKS G-1 was a promising candidate for integrated management of wheat stripe rust, functioning through both direct antagonism and induced systemic resistance coupled with growth promotion.