Objective evaluation of persimmon juiciness: Estimation of environmental variance and varietal differences

• An objective method for measuring the juice content of persimmon has been developed.
• In each cultivar there was no difference in the juice content among fruits picked on different days.
• The effect of genotype on juice content was highly significant
• The variance among trees within genotype or among years was negligible.
• There was a correlation between the juice content in this study and the evaluation by a sensory test.

Juiciness is one of the most important traits affecting fruit eating quality. In this study, we developed an objective method for evaluating the juice content of Japanese persimmon (Diospyros kaki Thunb.). Columns extracted from the flesh of fruits were homogenized using a disposable syringe, and then the homogenate was centrifuged. The weight of the supernatant was expressed as a percentage of the total weight of the fresh column sample. The fruits of eight Japanese persimmon cultivars were harvested three times during their respective commercial harvesting season, and there was no significant difference in the juice content among the fruits picked on different days. Genetic and environmental variances were estimated by ANOVA and the results showed that the effect of genotype on juice content was highly significant, whereas the variance among trees of the same genotype or between years was negligible. This indicated that in persimmon breeding, the juiciness of one cross-seedling could be evaluated using fruits from one tree in one year. Twelve pollination-constant and non-astringent persimmon cultivars were tested and ‘Taishu’ had the highest juice content (61.5%). A correlation was observed between the juice content in this study and their evaluation by a sensory test, which indicates that the juice content could be a useful indicator of sensory juiciness. The juice contents of five cultivars, whose sensory juiciness was evaluated as juicy, included ‘Fuyu’, were more than 40%. These results suggest that our method could facilitate breeding programs for developing new persimmon cultivars with high eating qualities.