UV-C Radiation Affects Gray Mold Decay in Citrus

The effects of UV-C radiation (254 nm, 290 mu W cm(-2)) on decay caused by gray mold (Botrytis cinerea Persoon) and scoparone accumulation in the flavedo of Satsuma mandarin (Citrus unshiu Marc., Unshiu), 'Kiyomi' tangor (C. unshiu x C. sinensis), Hyuganatsu (C. tamurana Hort. ex Tanaka), and 'Eureka' lemon (C. limon Burm. forma 'Eureka') was studied. Specimens were inoculated with gray mold mycelia by wounding the flavedo 4 days after the fruits were subjected to UV radiation. In control trials, untreated fruits were inoculated with the mycelia. The decay rate rapidly increased for 3-4 days after inoculation in all fruits except lemon. Control specimens of Satsuma mandarin, 'Kiyomi' tangor, and Hyuganatsu fermented 7 days after treatment. Compared with the control specimens, UV-irradiated specimens showed delayed decay, except 'Kiyomi' tangor and lemon. The diameter of the decayed area in UV-C treated Satsuma mandarin, 'Kiyomi' tangor, and Hyuganatsu showed inhibition at 4-5 days after inoculation. However, the diameter of the decayed area in lemon showed inhibition within 6 days after inoculation. After 7 days of inoculation, accumulation of scoparone in the flavedo of citrus fruits varied between species and fruits subjected to different treatment conditions. Scoparone accumulated in the flavedo of all citrus fruits except lemon, and concentrations changed after fruits were subjected to UV radiation and inoculated with gray mold. The extent of scoparone accumulation in the fruit flavedo was cultivar-dependent.