Abstract
Oriental persimmons (Diospyros kaki Thunb.; 2n = 6x = 90) are classified into four types depending on the astringency loss on the tree and its influence by seed: pollination constant non-astringent (PCNA), pollination variant non-astringent (PVNA), pollination variant astringent (PVA), and pollination constant astringent (PCA). Among these types, PCNA is the most important for breeding because its fruits show a stable loss of astringency on the tree. Two PCNA types, Japanese PCNA (J-PCNA) and Chinese PCNA (C-PCNA), have originated independently in Japan and China, respectively, and astringency loss in fruits of these types is controlled by different genetic mechanisms. In this study, we studied the relationship between the C-PCNA trait and fruit shape in progenies of the C-PCNA cultivar ‘Luo Tian Tian Shi’ × ‘Yotsumizo’ (PCA), ‘Iwasedo’ (PCA), and ‘Okugosho’ (J-PCNA). Since no J-PCNA offspring are yielded theoretically, all PCNA offspring are assumed to be the C-PCNA genotype. The fruit shape index, longitudinal diameter, and seed length were significantly greater in the PCNA than in the non-PCNA offspring. Fruits of the PCNA offspring have a flatter shape than those of the non-PCNA offspring. In contrast, the transverse diameter was not significantly different between the PCNA and non-PCNA progenies. The average fruit weight was larger in the PCNA than in the non-PCNA offspring, in which the difference was not significant. The length of the minor axis of the parenchyma cell in the fruit showed no significant difference between the PCNA and non-PCNA offspring, but fruits of the PCNA offspring had approximately 10% significantly smaller cells in the major axis and total area of the parenchyma cell. These results suggest that the C-PCNA fruit is repressed and/or reduced in terms of longitudinal growth of the fruit cell. The prevention of proanthocyanidin accumulation in the fruit may possibly have been an indirect effect on fruit growth. In addition, since ‘Luo Tian Tian Shi’ has only one dominant allele for the PCNA trait, the neighboring locus may have a strong effect on the trait that represses longitudinal growth of the fruit.
