Phenotypic Diversity and Relationships of Fruit Traits in Persimmon ( Diospyros kaki Thunb.) Germplasm Resources

Persimmons ( Diospyros kaki Thunb.) are a characteristic Chinese fruit and account for a large planting area in China. The evaluation and selection of persimmons that are astringent without softening play an important role in modern breeding programs. However, the phenotypic variability and diversity of some representative traits in the natural population of persimmon germplasm without softening are still unclear. In this study, 56 traits from 150 samples of D. kaki collected in East Asia were used to evaluate phenotypes and correlations using principal component analysis (PCA) and cluster analysis. The results show that the mean coefficient of variation for the persimmon germplasm traits was 26.19%, and significant variations in phenotypic traits were observed. The frequency distribution maps of most of the characteristics showed obvious normal distribution characteristics. The analysis of the correlations between the traits showed that the most significant positive correlations had correlation coefficients close to 0.7. For example, seed width was highly and significantly correlated with fruit longitudinal and transverse width (0.796 and 0.786), and pith height was highly and significantly correlated with seed length (0.816). Moreover, the correlations between fruit traits and support traits, such as those related to the fruit handle and sepals, were significant, and the coefficients of the correlations between sepal width and fruit traits were 0.671 to 0.739. Fruit water content was negatively correlated with the soluble solids content (−0.623). Principal component analysis reduced 38 traits to 8 principal components, explaining 82.459% of the total variations, which were related to fruit size, seed, pith, color, fruit hardness, and soluble solid content; thus, persimmon germplasm could be divided into three major categories according to the sizes and shapes of the traits, and the first cluster was divided into two subcategories. The first subclass of fruits is medium size and shape; the second subclass of fruits is small in all traits; the second cluster is of high-quality and large fruits, optimal in all traits; and the third cluster is of medium to high-quality and oblate fruits. The results of this study are important for genetic improvement, diversity conservation, and resource utilization regarding persimmons and further research in this regard.