Pre-exposure to UV-B irradiation induces antioxidant enzymes and mitigates Fusarium acutatum stress in shallot (Allium cepa L.).

Shallot (Allium cepa var. aggregatum) productivity is often limited by fungal diseases, particularly twisted disease caused by Fusarium acutatum. This study evaluated the effects of UV-B pre-exposure (150 min) on enhancing plant resistance under greenhouse conditions using four treatments: control, UV-B, F. acutatum, and UV-B + F. acutatum. UV-B pre-treatment significantly reduced disease incidence, severity, and the area under the disease progress curve (AUDPC) compared with infected plants without UV-B exposure. Although infection suppressed growth, UV-B pre-exposure alleviated these effects by maintaining higher plant height, root length, and biomass. UV-B also increased the photosynthetic pigment content, phenolic accumulation, and the activities of antioxidant enzymes, including catalase and peroxidase. LC-MS/MS metabolomic analysis revealed an increased abundance of metabolites associated with stress signaling, antioxidant responses, and defense-related metabolic pathways. The combined UV-B and pathogen treatment showed coordinated metabolic adjustments, indicating that UV-B priming enhances shallot tolerance to F. acutatum while sustaining growth, offering a sustainable disease management strategy.