Bifunctional Phyto-Synthesized Nano Silver for Mitigating Salinity-Induced Dormancy and Associated Fungal Infections...

Salinity-induced dormancy associated with fungal infection during germination in plants is the major contributor to abiotic and biotic stress, leading to a loss in crop productivity. The present study has been designed to evaluate the dual functions of Cymbopogon citratus-derived silver nanoparticles (CC-AgNPs) for enhancing the germination and prevention of Aspergillus niger (ATCC 6275) infection in seeds of Brassica juncea. AgNPs were synthesized using the cell-free aqueous extract of C. citratus followed by their characterization using LC-MS at variable voltage for trace level detection of compounds responsible for bio-reduction. The extract contained metabolites belonging to alkaloids, flavonoids, amino acid, and saponins. UV-Vis spectra revealed AgNP synthesis with a peak at 430 nm and stability for up to 180 days. Additionally, FTIR peaks demonstrated the presence of capped bioactive as reducing and stabilizing agents. TEM analysis depicted an AgNP size of 33 nm and spherical. Salt-stressed B. juncea seeds were primed with 100 ppm of CC-AgNPs, which significantly increased the germination rates and total seedling growth. This has been mainly favored by the restoration of proteins involved in germination, the antioxidant potential of green nano-silver, along with ameliorating amylase activity (15.53 ± 0.3 mg g^-1 fresh weight min^-1) for increasing soluble sugars (15.37 ± 0.3 mg g^-1 fresh weight) to support the germination process. Furthermore, CC-AgNPs showed antifungal activity against A. niger as demonstrated by radial growth inhibition assay. Machine learning models, including Extra Trees, CatBoost, XGBoost, and Ensemble Averaging, have also been employed to predict seedling growth performance under AgNP treatment, enhancing the predictive and analytical strength of the study. Molecular docking results revealed that Ag in CC-AgNPs collectively mediate the antifungal activity by interacting with specific domains of fungal protein chitin deacetylase. Also, these CC-AgNPs are safe to use, as examined by biocompatibility assays on soil microbiota, human RBCs, and human skin fibroblast cell lines. The results herein prospect the employment of phyto-synthesized AgNPs for nanospray applications in the field, mitigating not only the salt-induced seed dormancy but also battling fungal infections during seed germination.