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 40mM, was vacuum-infiltrated at 30 kPa for 8min at 20 ∘C. Methyl jasmonate orMeSA vapor treatmentswere applied separately at 50 and 100 𝛍Mby 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, orMeSA 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 40mM 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 themaintenance of the epidermis structure. Thiswas confirmed by scanning electron microscopy (SEM)micrographs