Carbohydrate Accumulation and Color Development in Watermelon

Watermelon [ Citrullus lanatus (Thunberg) Matsumura and Nakai], cultivars ‘Allsweet’, ‘Charleston Gray’, ‘Crimson Sweet’, and ‘Iopride’ were grown from transplants at Ames, Iowa, harvested at 4-day intervals for a total of 11 harvests. Carbohydrates from fruit juice extracts were determined by high-pressure liquid chromatography, and flesh color was determined by using a colorimeter. The reducing sugars, fructose and glucose, generally increased in concentration from 20 to about 36 days after anthesis and thereafter declined in each of the 4 cultivars. Sucrose was measurable in the fruit tissue 20 days after anthesis and thereafter increased. Total sugar concentration increased from 20–60 days after anthesis, with its most rapid increase occurring between 20 and 36 days. For the 4 cultivars sampled, relative sweetness index and total sugar concentration values were similar. Results confirm that ‘Charleston Gray’ develops its maximum red flesh color before reaching maximum sweetness. Such a developmental pattern may have a negative affect on per capita consumption when fruits are harvested on the basis of flesh color rather than edible quality.