Postharvest mandarin rind disorder: Insights into varietal differences and preharvest treatments effects on postharvest quality

Authors: REZK, ALAAELDIN - University Of California, Riverside; PERVAIZ, TARIQ - University Of California, Riverside; DOUHAN, GREG - University Of California, Riverside; Obenland, David - Dave; ARPAIA, MARY - University Of California, Riverside; EL-KEREAMY, ASHRAF - University Of California, Riverside

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2024
Publication Date: 4/9/2024
Citation: Rezk, A., Pervaiz, T., Douhan, G., Obenland, D.M., Arpaia, M.L., El-kereamy, A. 2024. Postharvest mandarin rind disorder: Insights into varietal differences and preharvest treatments effects on postharvest quality. Plants. 13(8). Article 1040. https://doi.org/10.3390/plants13081040.
DOI: https://doi.org/10.3390/plants13081040

Interpretive Summary: The citrus industry loses a significant amount of mandarin fruit either before or shortly after harvesting due to rind disorder. This disorder happens to different citrus cultivars and occurs in the fall, particularly after a rain. The damage begins as irregular water-soaked areas and develops into dark-brown lesions that can cover large portions of the fruit surface. In this study we attempted to understand and control the occurrence of the disorder in ‘Owari’ Satsuma mandarins under California conditions. We found that the outer portion of the tree canopy had more damage than the inner portion and that spraying either 2,4-D, gibberellic acid, or VaporGard when the fruit begin to turn orange reduces the damage. In addition, the treatments gave other benefits to ‘Owari’ and other varieties tested during cold storage. This research provided potential means for reducing loss of fruit due to this rind disorder.

Technical Abstract: The citrus industry loses a significant amount of mandarin fruit either before or shortly after harvesting due to rind disorder. Different citrus cultivars are impacted by a physiological rind disorder that lowers fruit quality and marketability. Although the primary etiology of this condition is unknown, changes in relative humidity (RH) and rind water status can make it worse. The damage is initiated in the fall, especially following rain. It begins with irregular water-soaked areas that develop into dark-brown, necrotic lesions covering large portions of the fruit’s surface. The damage is evident in some citrus types such as Satsuma Owari mandarins and other cultivars. In this study, we attempted to understand and control the occurrence of this kind of rind disorder in Satsuma Owari mandarins growing under California conditions. Our data showed that fruit located in the outer part of the canopy suffer more than fruit in the interior canopy. We were able to reduce this damage in Satsuma Owari mandarins by applying 2,4-dichlorophenoxyacetic acid (2,4-D) at 16 milligrams/Liter (mg/L), gibberellic acid (GA) at 20 mg/L, or Vapor Gard® at 0.5 percent (v/v) at the color break stage. However, GA caused a delay in color development by approximately four weeks. GA-treated fruit changed their color completely four weeks after the control, and the rind damage was at a very low percentage. Delaying rind senescence could be a good strategy to reduce the damage in Mandarin orchards. Data showed that in addition to the benefits of the different treatments on preventing rind disorder at harvest, they have some beneficial effects during storage for four weeks either at 0.5 or 7.5 °C.