Variation in carbohydrate content during ripening in two clones of pepino

Abstract

Fruits from pepino (Solanum muricatum Aiton) clones ‘Sweet Long’ and ‘Sweet Round’ were harvested at three stages of ripeness (green, turning and ripe). Changes in the carbohydrate fraction (total and free sugars, soluble and insoluble fibre) during on-bush ripening were evaluated in an early and a late crop in the autumn–winter cycle. Significant differences in composition were found for the effects of clone, crop and their interaction. This indicates that there is a considerable variation in the physiology of ripening. We found that total carbohydrate content was on average higher in ‘Sweet Long’ than in ‘Sweet Round’ and higher in the late crop than in the early one. Crossover interaction was detected for sugar content in the two clones, so that in the late crop the clone with highest sugar content was ‘Sweet Long’ while in the early crop it was ‘Sweet Round’. Pepino fruit contains slightly higher amounts of fructose than glucose, and contents of both sugars do not change dramatically during ripening. However, there is a sharp increase in sucrose as ripening progresses. Sucrose content in green fruits is very low or not detectable, while it is the predominant sugar when ripe, accounting for about 50% of the total sugars. The ripening process is characterised by a decline in insoluble fibre accompanied by an increase in total sugars and accumulation of sucrose. The important interaction clone × growing cycle indicates that selection for high sugar content should be carried out independently for each growing cycle. © 2000 Society of Chemical Industry