Quantitative characterization of fruit shape and its differentiation pattern in diverse persimmon (Diospyros kaki) cultivars

There is considerable diversity in fruit shapes among persimmon (Diospyros kaki) cultivars. Although fruit shape is one of the most important traits affecting the commercial quality of fruits, quantitatively characterizing fruit shape features remains difficult. The objective of this study was to develop a reliable method for quantitatively analyzing persimmon fruit shapes, and to clarify the fruit development patterns as well as their relationships to the shapes of other organs across cultivars. Using 153 persimmon cultivars and two wild Diospyros relatives, we evaluated two-dimensional pictures of longitudinal and transverse fruit sections with elliptical Fourier descriptors (EFDs) and the SHAPE program. Principal component analysis (PCA) using each EFD generated representative vectors, which elucidated the fruit shape diversity among the cultivars. Additionally, a PCA of the EFDs quantified two major components of the variability in the shapes of longitudinal fruit sections, namely the ratio of length to diameter and the fruit apex shape. Seasonal characterizations of the first principal component revealed the fruit shape development patterns. The fundamental shapes in the longitudinal direction were coordinately determined during the early developmental stages across cultivars. Furthermore, a quantitative characterization of persimmon fruit, seed, and leaf shapes unveiled correlations between these traits. The data presented herein indicate that combining EFDs and PCA enables the quantitative analysis of persimmon organ shapes, which may be related to various quantitative indices.