Effects of UV-B irradiation on the induction of physiological traits and defense enzyme activities in shallots ( <i>Allium cepa</i> L.) against <i>Fusarium acutatum</i> infection

Shallots (Allium cepa L. Aggregatum group) are highly susceptible to twisted disease caused by Fusarium spp., particularly F. acutatum, which severely reduces yield. This study aimed to assess the potential of UV-B irradiation to enhance shallot resistance against F. acutatum infection. A greenhouse experiment was conducted in which shallots were inoculated with F. acutatum and exposed to UV-B for 50, 100, or 150 min. Growth performance, physiological traits, and biochemical markers were evaluated. Results showed that UV-B irradiation for 50 min and 100 min significantly reduced disease incidence, disease severity, and the area under the disease progress curve (AUDPC) compared to controls (p < 0.05). UV-B irradiation for 100 min also effectively induced oxidative stress, stimulating phenol accumulation (p < 0.05). Both 100 min and 150 min UV-B irradiations enhanced plant defense mechanisms by sustaining high peroxidase (POD) and catalase (CAT) enzyme activities (p < 0.05). Additionally, shallot plants receiving optimal UV-B doses exhibited less leaf shrivelling and higher survival rates. In conclusion, UV-B irradiation for 100 min and 150 min has the potential to significantly enhance the resistance of shallot plants to F. acutatum infection.