Estimation of the proportions of offspring having soft fruit and juicy fruit as evaluated by sensory tests in Japanese persimmon

Firmness and juiciness are important fruit attributes targeted in the breeding of Japanese persimmon (Diospyros kaki Thunb.). To facilitate the efficient production of cultivars with soft and juicy fruit, we successfully used the mid-parental values (MP) of sensory evaluations as independent variables in logistic regression models to estimate the proportions of offspring from a given cross that would have soft fruit and juicy fruit. The best model for estimating firmness contained only the MP for firmness (MPf) as an explanatory variable, whereas the best model for juiciness contained both the MP for juiciness (MPj) and the MPf as explanatory variables. The regression lines from these models suggested that crosses with a low MPf and high MPj can increase the proportion of offspring that have soft fruit and juicy fruit, respectively. However, the slopes of the regression lines for both firmness and juiciness were gentle, indicating that genetic segregation in offspring is wide for both attributes. We infer from these data that softer and juicier fruit can be bred from parents having only moderate ratings for these traits.