Blue mold caused by Penicillium italicum Wehmer is the major postharvest disease infecting satsuma mandarin fruits. We studied the effects of simultaneous ultraviolet (UV)-B and (UV)-C irradiation on the spore germination of P. italicum in vitro, scoparone production on the flavedo tissue, blue mold symptom occurrence on the inoculated fruit and internal fruit quality, peel color and rind injury in Citrus unshiu Marc. ‘Aoshima unshu’. The UV irradiation inhibited the P. italicum growth in vitro. In particularly, the UV-C + UV-B light for 10 s (UV-C:UV-B; 0.2:0.25 kJ∙m-2) reduced spore germination by 91%, 48 hours after inoculation. Subsequently, scoparone production on UV-treated fruit was observed. Additionally, disease incidence, soft rot area diameter, and mycelial growth diameter on the fruit treated with UV-C (2.4 kJ∙m-2) + UV-B (3.0 kJ∙m-2) irradiation 72 hours before inoculation were examined. The diameter and the incidence of soft rot areas were not reduced significantly by UV irradiation 5 days after inoculation. However, UV-C + UV-B irradiation, and UV-C irradiation reduced the diameter of mycelial growth on fruits. Additionally, UV-B + UV-C irradiation was effective at reducing the incidence of mycelial growth. UV-C at 2.4 kJ∙m-2 + UV-B at 3.0 kJ∙m-2 irradiation did not affect fruit quality with respect to soluble solid concentration, titratable acidity, peel color or rind browning.
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