Enhancing Water Deficit Stress Tolerance in Wheat: Synergistic Effects of Silicon Nanoparticles and Plant Growth-Promoting Bacteria

Abstract Water deficit stress significantly reduces grain yield in bread wheat, requiring improved tolerance in cultivars. Despite recent breeding advancements, enhancing tolerance remains crucial. Plant growth-promoting bacteria (PGPB) and silicon (Si) independently boost drought resistance through different mechanisms, but their combined effects are understudied. This research explored the combined impacts of silicon dioxide nanoparticles (SiO2 NPs) and native PGPB on wheat's morphophysiological and nutritional responses under water deficit stress. The study tested various SiO2 NP concentrations (control, soil application of 100 and 200 mg/kg, and foliar application of 200 mg/kg) and PGPB strains (no bacterium, Pseudomonas fluorescens p-187, and Pseudomonas putida p-168). Results showed that SiO2 NPs significantly improved wheat tolerance to water stress, increasing shoot dry weight by 4.40 g/pot with 100 mg/kg Si-NPs and Pseudomonas fluorescens p-187 compared to the control, and root dry weight by 1.05 g/pot with foliar application of 200 mg/kg Si-NPs and Pseudomonas putida p-168. SiO2 NPs and PGPB also boosted N, P, K, and Si concentrations in wheat shoots, reduced malondialdehyde content, and increased superoxide dismutase and glutathione peroxidase activities. The best performance was achieved with 200 mg/kg Si-NPs and Pseudomonas fluorescens p-187. The study confirms that combining Si sources with PGPB effectively enhances wheat's drought tolerance. This synergistic approach offers an environmentally sustainable strategy to bolster crop resilience against water deficit stress, ensuring better wheat yield in drought-prone conditions.