OPTIMIZATION OF DEGREENING OF EARLY-SEASON SPONTANEOUS MUTATIONS OF 'ORONULES' MANDARINS

Degreening is a postharvest treatment during which citrus fruit are exposed to ethylene in order to accelerate external color change and so render the fruit more acceptable for marketing. However, ethylene can promote alterations associated to senescence specially in the area of calyx. Recently, new degreening treatments combining different periods with and without ethylene exposure have been reported to be effective in reducing the calyx disorders of early-season citrus fruit. In the present study, fruit from ‘Oronules’ mandarins and four of its mutations – ‘Prenules’, ‘Basol’, ‘Clemenrubi’ and ‘Orogros’, were degreened during different periods with and without ethylene application over a total of 120 h at 21°C, and 90-95% RH. Afterwards, fruit were submitted to a cold-quarantine treatment (1°C, 16 d) plus shelf-life (20°C, 95% RH for 7 d). In all cultivars, the shorter time of exposure to ethylene, the lower incidence of calyx disorders. Treatment comprising 48 h ethylene exposure and 72 h without ethylene was sufficient to reach an commercially acceptable external color (CCI > +6). However, to obtain the typical color of the cultivar, treatment with 72 h with ethylene plus 48 h without ethylene is needed. At this degreening condition, ‘Prenules’, ‘Basol’ and ‘Clemenrubí’ cultivars showed lower susceptibility to calyx senescence than ‘Oronules’. None of the treatments affected the internal fruit quality of any cultivar.