Relationship among Sugars, Organic Acids, Mineral Composition, and Chilling Injury Sensitivity on Six Pomegranate Cultivars Stored at 2 °C

Abstract

Pomegranate is a sensitive fruit to chilling injury (CI) during storage at temperatures below 7 °C. However, sensitivity of pomegranate to CI is dependent on cultivar and exposure times to low temperatures. In this work, the sensitivity to CI of six pomegranate cultivars (Punica granatum L.) ‘Wonderful’, ‘Kingdom’, ‘Bigful’, ‘Acco’, ‘Purple Queen’, and ‘Mollar de Elche’, was evaluated after 30 d at 2 °C plus 2 d at 20 °C. Among cultivars, there was a great variability in the sensitivity to the appearance of CI symptoms. ‘Kingdom’ cultivar was the most CI sensitive and ‘Mollar de Elche’ cultivar was the least sensitive cultivar. CI symptoms were greater in the internal part of the skin than in the external part, although no correlation was found between ion leakage (IL) and CI severity after cold storage. However, both, external and internal CI index were correlated with the IL at harvest, with Pearson correlation of 0.63 and 0.80, respectively. In addition, this variability to CI among cultivars could also be due to composition and tissue structures in arils and peel. The solute content of the arils (anthocyanins, sugars, and organic acids, in particular citric acid), showed high correlations with CI sensitivity, with Pearson correlations (r) of 0.56 for total soluble solids, 0.87 for total acidity, 0.94 for anthocyanins, −0.94 for oxalic acid, 0.87 for citric acid, 0.62 for tartaric acid, −0.91 for malic acid, 0.8 for sucrose, and 0.71 for glucose, which can leak to the inner surface of the peel causing browning reactions. In addition, the high peel Ca/K ratio could play an important role on increasing fruit tolerance to CI, since it was negatively correlated with the internal and external CI indexes.

Biochemical and molecular changes in peach fruit exposed to cold stress conditions

“…In particular, peach fruit with higher concentration of sugars are more resistant to CI than those with lower concentrations (Brizzolara et al 2018 ; Tanou et al 2017 ; Wang et al 2013 ; Wu et al 2016 ; Yu et al 2015 ; Yu et al 2017 ; Zhang et al 2020 ) and in turn CI causes a decrease of sugars in fruit (He et al 2018 ; Monti et al 2019 ). The link between sugar metabolism and CI has been also reported in fruits such as pear, banana, tomato, bell pepper, and pomegranate (Delgado‐Vargas et al 2022 ; Gómez et al 2009 ; Liu et al 2019a ; Lorente-Mento et al 2023 ; Xu et al 2023 ; Yang et al 2023 ). Several studies reported how the increased tolerance to CI observed in fruits in response to the application of exogenous treatments was connected to the enhancement of sugar metabolism (Zhang et al 2021 ).…”