Induction of Physiological Resistance Against <i>Fusarium</i> Wilt in <i>Cucumis sativus</i> Using <i>Bacillus aryabhattai</i> Z‐48 and <i>Bacillus cereus</i> Z‐53

Cucumis sativus (L.) is a high-value crop renowned for its nutritional content, including vitamins, minerals, and antioxidants. However, its productivity is severely hindered by Fusarium wilt, a soil-borne disease caused by Fusarium oxysporum f. sp. cucumerinum. This study investigated the biocontrol potential of two plant growth-promoting rhizobacteria (PGPRs), Bacillus aryabhattai Z-48 and Bacillus cereus Z-53, in managing Fusarium wilt under controlled pot conditions. Treatment with PGPRs significantly enhanced C. sativus growth, including root and shoot length, and fresh and dry biomass, compared to both pathogen-inoculated and uninoculated controls. Disease severity was reduced by 34% and 27% in C. sativus plants when treated with B. aryabhattai Z-48 and B. cereus Z-53, respectively. B. aryabhattai Z-48-treated plants exhibited significant increases in defense-related enzyme activities, including polyphenol oxidase (78%), phenylalanine ammonia lyase (3.1-fold), and peroxidase (89%). Physiological parameters were also improved in PGPRs inoculated plants, such as total chlorophyll (29%), carotenoids (36%), phenolics (14%), flavonoids (91%), and protein content (10%) compared to pathogen-infested plants. LC-MS-based metabolomic profiling revealed significant metabolic reprogramming, with upregulation of key stress tolerance, antioxidant, and defense-related compounds, including quercetin, DL-phenylalanine, gluconic acid, xanthophyll, guanosine, and benzoic acid in the PGPR-treated plants. These metabolic shifts corroborated the physiological improvements, indicating enhanced systemic resistance and improved plant vigor. Overall, the results demonstrated that B. aryabhattai Z-48 not only suppressed Fusarium wilt but also promoted C. sativus growth through physiological, biochemical, and metabolic modulation. Further research should explore the practical field application of these strains in pathogen-contaminated soils for sustainable crop production.