Exogenous glycine betaine treatment alleviates low temperature-induced pericarp browning of 'Nanguo' pears by regulating antioxidant enzymes and proline metabolism

The effect of glycine betaine (GB) on chilling injury (CD-induced pericarp browning in 'Nanguo' pears was investigated during shelf life at 20 degrees C after storage at 0 degrees C for 120 d. GB treatment alleviated the severity of browning in Nanguo' pears as represented by lower browning index (BI) and browning incidence. Membrane lipid peroxidation in GB-treated fruit was lower than that in the control, and membrane integrity was maintained in good condition. The activities and expression of ascorbate peroxidase (APX), catalase (CAT), and superoxide dismutase (SOD) were higher in GB-treated fruit than in control fruit. Furthermore, significantly higher proline content, proline synthesis key enzyme activities, and gene expression were observed in the treated fruit, including ornithine d-aminotransferase (OAT) and Delta 1-pyrroline-5-carbox-ylate synthetase (P5CS), which were consistent with the browning tendency. In a nutshell, GB treatment can effectively alleviate pericarp browning of cold-stored 'Nanguo' pears by regulating antioxidant enzymes and proline metabolism.