MANAGING CHILLING INJURY IN FRUITS

Abstract

Most tropical and subtropical fruits are susceptible to chilling injury, mainly manifested as pitting, surface or internal browning, failure to ripening, development of a woolly or leathery texture, and decay. The development of these chilling injury symptoms negatively affects fruit quality and thus shortens storage life. Chilling injury of fruits can be alleviated by physical techniques such as low temperature conditioning, heat treatment, controlled or modified atmosphere storage, waxing, and UV-C irradiation, by chemical treatments with methyl jasmonate (MeJA), methyl salicylate (MeSA), γ-aminobutyric acid (GABA), 1-methylcyclopropene (1-MCP), nitric oxide, oxalic acid, or other natural compounds and genetic engineering. Treatment with MeJA enhances antioxidant activity, increases endogenous GABA and proline content and maintains a higher degree of unsaturation of membrane lipid in loquat fruit. GABA treatment enhances the accumulation of endogenous GABA and proline, induces higher antioxidant activity, and maintains higher adenosine triphosphate (ATP) content and energy charge in peaches. The combination of heat with MeJA or MeSA treatment has a synergistic effect on alleviating chilling injury and inducing higher antioxidant activity in peach fruit. For loquat, avocado, pineapple, and persimmon fruits whose chilling injury is enhanced by increased ethylene production, 1-MCP can be used to reduce its development. Low temperature conditioning activates the expression of membrane lipid modification enzymes such as fatty acid desaturase (FAD) and lipid transfer protein (LTP), whereas heat treatment induces the expression of various stress-related genes, including heat shock proteins (HSPs), dehydrin and universal stress protein (USP), increases antioxidant activity and maintains membrane stability in citrus fruits. Genetic engineering has the potential to enhance chilling tolerance by generation of genetically-modified fruits with overexpressed genes that encode HSPs and antioxidant enzymes.