Endophytic Aspergillus niger and Aspergillus oryzae improve growth, antioxidant defense, and ion homeostasis in maize under salinity stress

Salt stress limits maize productivity worldwide, and sustainable strategies are required for stress alleviation. The current study assessed the ability of endophytic fungi Aspergillus niger (MA2) and Aspergillus oryzae (MA5), isolated from Moringa oleifera seeds and identified by rDNA sequencing (GenBank: PV616998, PV616999), to mitigate salinity stress in maize. Both the isolates exhibited considerable production of indole-3-acetic acid, proline, phenolics, flavonoids, and sugars, which was enhanced under saline conditions. The application of 200 mM NaCl significantly (p ≤ 0.05) reduced shoot/root growth, biomass, and photosynthetic pigments, depleted the endogenous IAA and gibberellic acid, disrupted the ionic balance (elevated Na⁺/Cl⁻; reduced K⁺, Ca²⁺, Mg²⁺, N, P), and increased oxidative damage (MDA, H₂O₂) with significant increases in osmolytes, antioxidant enzymes, and secondary metabolites. Inoculation with MA2 and MA5, confirmed by endophytic colonization and stomatal assessment, successfully restored photosynthetic pigments, growth parameters, and hormonal balance, optimized metabolite and antioxidant profiles, and reduced MDA compared to non-inoculated stressed controls. Fungal association also restored ionic homeostasis by reducing Na+/Cl- uptake and increasing K+, Ca2+, Mg2+, N, and P accumulation, thus restoring Na+/K+ and Na+/Ca2+ ratios important for salt tolerance. Principal component analysis (PC1 = 62.40% and PC2 = 24.81%) confirmed these physiological and biochemical changes with clear separation of inoculated and non-inoculated treatments. Collectively, MA2 and MA5 act as powerful biostimulants that promote maize salt tolerance through coordinated physicochemical, hormonal, and ionic regulation, offering a promising strategy to improve crop resilience under saline conditions.