Amelioration of postharvest chilling injury in sweet pepper by glycine betaine

• Glycine betaine (GB) at 1 mmol L−1 reduces chilling injury of sweet pepper at 3 °C.
• GB induces antioxidant gene expression in pepper fruits.
• GB induces enzyme activity of antioxidant enzymes in pepper fruit.
• GB improves the retention of pepper fruit quality at 3 °C.

The reduction in the quality of harvested green peppers due to physiological disorders resulting from chilling injury (CI) results in significant economic losses. In the current study, the ability of glycine betaine (GB, a stress-ameliorating compound) to reduce CI in sweet pepper was investigated. GB at 1 mmol L−1 significantly reduced CI in sweet pepper fruit during a sixteen-day period of storage at 3 °C followed by an additional 3 days at 20 °C. CI index, membrane permeability, chlorophyll content, ascorbic acid (ASA), and malondialdehyde (MDA) were assessed. The activities of a variety of antioxidant enzymes, including peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and lipoxygenase (LOX) were determined along with transcript levels. Results indicated that amelioration of CI in sweet pepper by GB was associated with a reduction in cellular leakage, MDA content, and lipid peroxidation in sweet pepper. Both gene expression and enzyme activity of POD, CAT, APX, and GR in GB-treated fruit were higher than levels in control fruit. These data suggest that GB increases chilling tolerance in pepper fruit by inducing antioxidant gene expression and enzyme activity, thus alleviating the potential injury resulting from CI.