Multi-method in vitro assessment of ultraviolet-C treatment against conidia and hyphal fragments of Botrytis cinerea

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Botrytis cinerea is a significant postharvest fungal pathogen responsible for substantial losses in a variety of fresh produce. Ultraviolet-C (UV-C) irradiation is a potential intervention that could reduce postharvest losses due to fungal disease. However, the diversity of fungal reproductive forms and lack of standardization in antifungal assessment methods complicate the evaluation of UV-C efficacy. This study evaluated the in vitro antifungal efficacy of UV-C against B. cinerea conidia and hyphal fragments (HF) treated in liquid suspension and on agar surfaces. B. cinerea viability was assessed using several methods: colony counts (from agar surface and suspension treatments), growth kinetics (suspension treatment), and conidial germination assays (suspension treatment). UV-C treatment caused significant, dose-dependent reductions in viability across all methods and for both reproductive forms. Surface treatments yielded the highest log reductions (>3.5 log reduction of conidia at 543.6 mJ/cm²), while suspension treatments showed comparatively modest reductions (~1–2 log reduction of conidia at 543.6 mJ/cm², depending on the method). Growth kinetics showed extended lag phases following UV-C exposure. Conidial germination was reduced by up to 95%, with diminishing efficacy at higher doses. While conidia generally exhibited greater sensitivity to UV-C than HF, the magnitude of inactivation varied by assay. A mixed-effects model confirmed that UV-C dose, reproductive form, and assessment method had a significant impact on fungal inactivation. IMPORTANCE This study systematically compared UV-C effects on conidia and HF using a multi-method in vitro approach, underscoring the utility of UV-C for fungal control and providing critical insights for designing effective, context-aware antifungal strategies. The results have practical implications for improving postharvest sanitation protocols and minimizing produce spoilage in storage and packing environments.