Variation of carotenoid, sugar, and ascorbic acid concentrations in watermelon genotypes and genetic analysis

The effects of flesh color, season, and test cross on carotenoid, sugar, and ascorbic acid contents of 20 watermelon genotypes with red, pink, orange, and yellow flesh were examined. Red- and pink-fleshed watermelons contained lycopene (4.8-47.8 mu g center dot g(-1) fresh weight), beta-carotene (< 3.7 mu g center dot g(-1)), and lutein (< 0.9 mu g center dot g(-1)) as the major carotenoids. The orange and yellow watermelons contained complex mixtures of prolycopene, lycopene, and beta-carotene with levels less than 7.4, 1.5, and 8.5 mu g center dot g(-1), respectively. There were also minor carotenoids, such as violaxanthin, lutein, neurosporene, and zeacarotene in the range of 0-1.4 mu g center dot g(-1). Total sugar contents ranged from 24 to 91 mg center dot g(-1), with sucrose, glucose, and fructose as the major sugars. The sugar profiles were divided into sucrose-, fructose-, and non-dominant groups. Higher percentages of glucose and fructose were negatively correlated with the total sugar content. Fairly-low levels of ascorbic acid, less than 28.2 mu g center dot g(-1), were measured, and some genotypes had nearly no ascorbic acid. There were only slight differences in ascorbic acid, sugar, soluble-solid, and total-carotenoid contents among 11 genotypes harvested in June and November. Five sets of test crosses showed various trends of heritability of carotenoids, sugars, and ascorbic acid in F-1 hybrids. In general, carotenoids and total sugar content tended to be inherited from the parent with lower carotenoid and sugar contents, respectively. Paralleled chemical analyses will be beneficial for efficient progress in breeding efforts and genetic research.