Methyl jasmonate alleviates chilling injury and regulates fruit quality in 'Midknight' Valencia orange

Susceptibility of sweet oranges to chilling injury (CI) restricts the utilisation of cold storage to its full potential to extend storage life and maintain fruit quality. The present investigation examined the role of postharvest methyl jasmonate (MJ) dips and different cold storage temperatures on the incidence of CI and fruit quality of 'Midknight' Valencia over two years. The fruit were dipped for 1 min in aqueous emulsions containing different concentrations 0.10, 0.25 or 0.50 mM of MJ and 'Tween 20' (0.01%) as a surfactant. The untreated fruit were used as the control. The fruit were stored at 4 degrees C or 7 degrees C for 90 d followed by 10 d simulated shelf conditions. MJ treatments, irrespective of the concentration applied, reduced CI in the fruit. The fruit treated with 0.25 mM MJ followed by 90 d cold storage and 10 d simulated shelf conditions were free from CI, irrespective of the cold storage temperatures. Dip treatments of 0.25 or 0.50 mM MJ reduced soluble solids concentration (SSC) and titratable acidity (TA); however, the SCC/TA ratio was higher when fruit was dipped in 0.25 mM MJ as compared with all other treatments. 0.25 or 0.50 mM MJ reduced concentrations of vitamin C and total antioxidants compared with all other treatments. Overall, 0.25 mM MJ is recommended as a treatment to reduce CI, while maintaining fruit quality attributes.