The isolated and combined impacts of ethanol and ethylene application on sugars and organic acids dynamics in ‘Elstar’ and ‘Nicoter’ apples

Abstract

The aim was to evaluate the isolated or combined effects of ethanol vapor (500 ppm) and ethylene treatments (150 ppm), on the ethylene production, respiration, sugars and organic acids dynamics of ‘Elstar’ and ‘Nicoter’ apples after harvest, during 14 d at 20 °C. Another aim was to identify at which step of fruit metabolism ethanol vapor acts. Fruit were exposed to ethanol vapor and/or ethylene for 24 h. Metabolites were evaluated at 0, 7 and 14 d at 20 °C. Ethanol vapor treatment significantly inhibited the effect of ethylene on the ethylene production and respiration, but had no significant effect on the starch metabolization and sucrose dynamics. Its application also resulted in higher succinate, malate and total organic acids concentrations. Ethanol application reduced significantly the sucrose conversion to glucose and fructose, while the ethanol + ethylene treatment resulted in high total sugars, fructose and sorbitol concentration after 14 d at 20 °C. The ethanol application (500 ppm) also affected conversion of succinate to fumarate, suggesting the succinate dehydrogenase activity as one possible action point of ethanol on the apple fruit metabolism. According to the PCA analysis, the combination of ethanol + ethylene treatments had a different response as their isolated application, affecting sugars and organic acids metabolism differently. Additionally, it can be verified that the response to treatments of both apple cultivars is differently affected by the holding time, being the response latter for ‘Nicoter’ apples when compared to ‘Elstar’.