Effects of Exogenous Abscisic Acid on Soluble Sugars and Sugar Metabolizing Enzyme Activities in Highbush Blueberry (Vaccinium corymbosum cv. Jersey) Fruits

Abstract

Abscisic acid (ABA) is a non-climacteric fruit ripening regulator having a potential to increase soluble sugars and sugar metabolizing enzyme activities. This study was to examine whether an exogenous ABA treatment affects color, firmness, soluble sugar contents, and sugar metabolizing enzyme activities in highbush blueberry fruits (Vaccinium corymbosum cv. Jersey) during ripening. ABA dipping at 500 ppm at 53 days after full bloom enhanced fruit skin coloration, and fruit softening, soluble sugar accumulation in blueberry fruits, suggesting a fruit ripening stimulatory effect. Analysis for the sugar contents revealed that the major soluble sugars in highbush blueberry fruits were fructose, glucose, and sucrose. With ABA treatment, the amounts of fructose, glucose, and sucrose were increased, and the increases of fructose and glucose were relatively higher than that of sucrose. Activities of the soluble sugar metabolizing enzymes, acid invertase, neutral invertase, sucrose synthase, and sucrose phosphate synthase were also affected by the ABA treatment. These results indicated that ABA stimulated ripening of highbush blueberry fruits by increasing sugar metabolizing enzyme activities.