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Genetic and environmental variances for fruit ripening time (FRT), fruit weight, and soluble solids concentration (SSC) in Japanese persimmon (Diospyros kaki Thunb.) were estimated. The variance among fruit within a tree was the largest among environmental variances. Therefore, using a large sample size per tree and per year effectively increased heritability, but the effect was minimal when more than five fruit were sampled. The variance among years was largest for SSC and smallest for FRT. Generally, the variance associated with the genotype × year interaction was as large as the tree × year interaction. The variance among trees within a genotype was negligible for all traits. Repeating measurements yearly was more efficient than replicating trees.

The expected proportion of individuals in progeny having genotypic values for fruit weight over a given selection criterion to the total individuals derived from a cross was estimated by multiple-regression analysis in which inbreeding coefficient (F) and midparental (MP) value were independent variables and progeny mean was the dependent variable in Japanese persimmon (Diospyros kaki Thunb.). A total of 117 seedlings from 39 crosses was used. Genetic differences of progenies among crosses could be explained solely by F and MP, the effect of the former being greater than the latter. The expected proportion of progenies with large fruit decreased as MP decreased and severely decreased as F increased. Based on the parental mean of 35 fruit on a single tree for 3 years, the proportion of individuals in progeny with fruit weight >200 g was estimated as 34%, 21%, and 12% for 0, 0.125, and 0.25 F values, respectively, in individual from a cross with MP = 200 g.

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SummaryOne hundred and eighty-eight cultivars of oriental persimmon (Diospyros kaki Thunb.) native to Japan were evaluated for fruit ripening time (FRT), fruit weight (FW), and soluble solids content (SSC). A high heritability for each of these traits was conserved in this population; the overall mean and SD of FRT, FW and SSC were early to mid-November and 15 days, 200 g and 72 g, and 17.0% and 1.7%, respectively. Subgroups of PCA (pollination constant-astringent) and PVNA (pollination variant-nonastringent) showed wide variations for each trait. As to mean values, the PVNA group had slightly earlier FRT and higher SSC than the PCA group but their FW were similar. PCNA (pollination constant-nonastringent) group showed the latest FRT and the SSC was intermediate between those of PCA and PVNA groups; whereas, PVA (pollination variant-astringent) had the earliest FRT with the lowest SSC. The PCNA and PVA groups had larger fruits than the PCA and PVNA groups. Variations in FRT and SSC of PCNA were characteristically small, which suggest that these cultivars evolved later than the others.There is a weak, negative correlation between FW and SSC and a weak, positive one between FRT and FW. The percentage of early ripening cultivars was higher in cultivars which originated in the northern areas of Japan in contrast to those developed in southern regions.