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Peiyan Li, Xiaolin Zheng, Md. Golam Ferdous Chowdhury, Kim Cordasco and Jeffrey K. Brecht

Effects of postharvest oxalic acid (OA) application on chilling injury (CI) in harvested mango fruit (Mangifera indica L.) were investigated using ‘Tommy Atkins’ fruit from Florida and ‘Zill’ fruit from Panzhihua. The OA was applied to harvested fruit as a 5 or 10 mm drench for 10 or 15 minutes at 25 °C. ‘Tommy Atkins’ fruit typically develop external CI symptoms while ‘Zill’ develops internal symptoms. Development of CI symptoms was significantly reduced in OA-treated ‘Tommy Atkins’ fruit stored for 18 days at 5 °C as was the rate of softening upon transfer to 25 °C for 4 days. However, OA treatment did not substantially control fruit decay. For ‘Zill’, CI development was significantly reduced in OA-treated fruit during storage at 10 °C for 49 days and subsequently for 4 days at 25 °C. In addition, membrane integrity was enhanced and the activities of the antioxidant system enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were elevated, although there were decreases in both hydrogen peroxide (H2O2) content and superoxide radical production in OA-treated fruit. The activities of some enzymes of the energy cycle were also elevated in the OA-treated fruit, including succinate dehydrogenase (SDH), cytochrome C oxidase (CCO), H+-adenosine triphosphatase (H+-ATPase), and Ca2+-adenosine triphosphatase (Ca2+-ATPase). Thus, OA may enhance CI tolerance in mango fruit by maintaining membrane integrity associated with enhanced antioxidant activity and regulation of energy metabolism. Application of 5 mm OA appears to be beneficial in controlling postharvest CI in mango fruit.

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Mingxiu Liu, Peng Wang, Xu Wei, Qing Liu, Xiaolin Li, Guolu Liang and Qigao Guo

Triploid loquat (2n = 3x = 51) has stronger growth vigor and larger leaves, flowers, and fruit compared with its diploid parental plant (2n = 2x = 34), but the effects of triploidization on the contents of flavonoids and phenolics in leaves and flowers, which are the most important antioxidant compounds for pharmacological applications, have not been reported. In this report, 58 triploid loquat genotypes and seven corresponding diploid parental cultivars were used to evaluate the effects of triploidization on the contents of total flavonoids and phenolics and the antioxidant activities of leaves and flower buds. The results showed that the contents of total flavonoids and phenolics and their corresponding antioxidant activities were higher in most of the triploid loquat genotypes than their diploid parents. The antioxidant activities of leaves and flower buds were significantly correlated with the total flavonoids and phenolics contents in both diploid loquat and triploid loquat. It could be inferred that triploidization could increase the contents of flavonoids and phenolics in leaves and flower buds of loquat. Notably, the contents of total flavonoids and phenolics of leaves in triploid genotype ‘H3/24’ were the highest, reaching 212.00 mg rutin equivalent (RE)/g DW and 93.06 mg gallic acid equivalents (GAE)/g DW, respectively, which were significantly higher than those previously reported. Such a valuable trait may be stacked with other triploid traits that are already established, such as larger vegetative organs and better tolerance to various stresses, as a feasible strategy for breeding loquat cultivars with high pharmaceutical potency.