Exogenous trehalose alleviates chilling injury of ‘Kim Ju’ guava by modulating soluble sugar and energy metabolisms

Changes in soluble sugars contribute to energy metabolism and membrane stability involved in cold acclimation of postharvest fruit. The aim of this study was to investigate the impacts of exogenous trehalose on soluble sugar and energy metabolisms in response to membrane stability and chilling injury (CI) of ‘Kim Ju’ guava fruit. Mature guava fruits were treated with 0 (control), 50, 100, 200 and 400 mM trehalose and stored at 8 °C for 14 d, followed by 4 d of shelf storage at 25 °C. Trehalose at 200 mM was the most effective in lowering CI while the fruit quality is still high. The trehalose-treated fruit exhibited a higher index of membrane stability and energy level accompanied by a rise in endogenous trehalose, sucrose, glucose 6-phosphate and fructose 6-phosphate levels but glucose and fructose levels were depressed. Moreover, trehalose treatment promoted the activities of sucrose synthetic enzyme including, sucrose phosphate synthase and sucrose synthase (synthesis) as well as trehalose hydrolytic enzyme such as trehalase and glycolytic enzymes including, hexokinase, fructokinase, phosphoglucoisomerase and pyruvate kinase. On the other hand, trehalose treatment reduced the activities of sucrose hydrolytic enzymes such as sucrose synthase (cleavage) and invertase. The increase in enzyme activities and soluble sugar levels by trehalose treatment improved the energy status and membrane stability during cold storage which inhibited CI development of guava fruit.