Sucrose metabolism in watermelon fruit is affected by fruit-setting method under plastic film greenhouses

Abstract

ABSTRACTFruit set represents the very first step of fruit development. This study investigated the effect of different fruit-setting methods [1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) treatment, artificial pollination, and honey bee pollination] on the concentrations of fructose, glucose, and sucrose, and the activities of sucrose metabolising enzymes of watermelon fruit under plastic film greenhouse conditions. No significant difference in fructose and glucose concentrations was observed among the three treatments at fully ripe stage of fruit [33 days after anthesis (33 DAA)]. However, artificial and honey bee pollination significantly increased sucrose concentration. Measurement of sucrose metabolising enzyme activities and correlation analysis demonstrated that the increased activity of SuSy-s (sucrose synthase, synthesis direction) is the key mechanism of increased sucrose concentration in the artificially pollinated and honey bee pollinated fruits. The concentrations of fructose, glucose, and sucrose were similar between artificially pollinated and honey bee-pollinated fruits at fully ripe stage (33 DAA). Therefore, we can conclude that artificial and bee pollination can improve the sweetness of watermelon fruit. In addition, the honey bee can provide a pollination service that is similar to that of artificial pollination for watermelon grown in a protected cultivation system.