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.