Preliminary Study on the Relationship Between Fluorescence and Pitting of Citrus

Huating Dou, Mohamed A. Ismail, Peter D. Petracek


Five studies have been performed this year on white 'Marsh' grapefruit and 'Fallglo' tangerines to establish the relationship between fruit fluorescence and peel pitting. Fruit fluorescence was measured before harvesting, at harvesting, and after packing. The results of these studies show that greenish mature white 'Marsh' grapefruit usually had higher fruit fluorescence (average minimal fluorescence, Fo: 120; average maximal fluorescence, Fm: 750) than that of yellowish mature grapefruit (average Fo: 25; average Fm: 125). In contrast, the latter fruit pitted more (20%) than the former. Shellac wax resulted in relatively low fruit fluorescence, whereas fruit coated with carnauba wax had high fluorescence. The highest fruit fluorescence was found in non-waxed fruit among wax treatments. There is a positive relationship between fluorescence at harvest (both Fo, and Fm) and pitting of grapefruit in one out of three studies. In 'Fallglo' tangerines, no relationship was found between fruit fluorescence and pitting incidence. Fruit fluorescence measurements on-tree before and after color-break were similar in magnitude to those taken one day after fruit packing. Fluorescence may be a useful predictor of postharvest pitting when used in conjunction with other factors such as fruit maturity and turgidity.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283