Postharvest treatments with γ‐aminobutyric acid, methyl jasmonate, or methyl salicylate enhance chilling tolerance of blood orange fruit at prolonged cold storage

Abstract

BACKGROUND Blood orange is sensitive to chilling injury (CI) depending on cultivar and storage temperature. Postharvest treatments with γ‐aminobutyric acid (GABA), methyl jasmonate (MeJA), or methyl salicylate (MeSA) are known to alleviate CI. γ‐Aminobutyric acid aqueous solution, applied at 20 and 40 mM, was vacuum‐infiltrated at 30 kPa for 8 min at 20 °C. Methyl jasmonate or MeSA vapor treatments were applied separately at 50 and 100 μM by putting the fruit in 20 L plastic containers for 18 h at 20 °C. There have been no reports about postharvest treatments of GABA, MeJA, or MeSA on enhancing the tolerance of ‘Moro’ blood orange to chilling during long‐term cold storage at 3 °C for 150 days, which was the subject of this study. RESULTS All treatments significantly alleviated CI symptoms of blood orange manifested by lower electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H2O2) concentrations, and higher proline content in flavedo during storage. The largest effects were obtained with 100, 50 μM, and 40 mM for MeSA, MeJA, and GABA, respectively, which enhanced the activity of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD), and phenylalanine ammonia‐lyase (PAL). On the other hand, these treatments suppressed peroxidase (POD) and polyphenol oxidase (PPO) activities. CONCLUSION The mechanisms involved in enhancing the tolerance of ‘Moro’ blood orange to chilling could involve scavenging H2O2 by increasing the activity of antioxidant enzymes, higher PAL/PPO activity ratio, and osmoregulation by increasing proline content. These changes led to the maintenance of the epidermis structure. This was confirmed by scanning electron microscopy (SEM) micrographs. © 2019 Society of Chemical Industry

Changes in Bioactive Compounds, Antioxidant Activity, and Nutritional Quality of Blood Orange Cultivars at Different Storage Temperatures

“…The protocol for enzyme activities was the same that for flavedo tissue [ 21 ]. In brief, the enzyme activities of flesh were evaluated spectrophotometrically.…”

Susceptibility of Blood Orange Cultivars to Chilling Injury Based on Antioxidant System and Physiological and Biochemical Responses at Different Storage Temperatures

“…Blood oranges exhibit some responses at the cellular level after exposure to cold stress. The common responses include changes in cell structure, fatty acid saturation index, lipid peroxidation, electrolyte leakage (EL), proline content, hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), activity of antioxidant enzymes and epidermis structure, among others [8]. In addition, chilling stress can change the cellular metabolism and reduce cell energy status, leading to chilling injury (CI) symptoms such as scalding, rind pitting and necrotic areas, watery breakdown and browning [8,9].…”

“…The common responses include changes in cell structure, fatty acid saturation index, lipid peroxidation, electrolyte leakage (EL), proline content, hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), activity of antioxidant enzymes and epidermis structure, among others [8]. In addition, chilling stress can change the cellular metabolism and reduce cell energy status, leading to chilling injury (CI) symptoms such as scalding, rind pitting and necrotic areas, watery breakdown and browning [8,9]. Postharvest treatment by hot water dipping (HWD, 3 min at 50 • C) and hot air treatment (HAT, 37 • C for 48 h) on blood orange fruit during cold quarantine at 1 • C for 16 days, showed that HWD and HAT similarly reduced CI in all cultivars, and neither treatment caused visible damage to the fruit [10].…”

“…In addition, vacuum infiltration of putrescine alleviated CI and maintained fruit quality of two blood orange cultivars ('Moro' and 'Tarocco') during cold storage [1]. It has been reported that enhancing chilling tolerance in blood orange fruit exposed to chilling stress depended on inducing antioxidant enzymes, increasing phenylalanine ammonia-lyase (PAL) activity and promoting the proline content and subsequently achieving increased maintenance of membrane integrity [8].…”

“…Blood oranges are sensitive to cold stress and exhibit CI symptoms when stored at 5 • C, depending on cultivars and storage temperatures [8]. However, storage of blood orange at cold temperatures is necessary for extending their postharvest life [1].…”