Persimmon (Diospyros kaki Thunb.) is an economically important tree with a long history of cultivation in China. So far, a total of approximately 1000 varieties have been found in China. To systematically evaluate the diversity of persimmon fruit quality, 22 quality measures of appearance, intrinsic, and sensory quality were evaluated using 61 typical persimmon fruit. According to the findings, the coefficient of variation (CV) of 15 appearance and intrinsic quality index values ranged from 13.81% (fruit shape index) to 165.80% (firmness), and the CV values of 7 intrinsic quality attributes were all higher than 50%, with the CV of total polyphenols and ironic soluble pectin contents (ISP) being as high as 159.82% and 143.80%, respectively. These findings showed that several persimmon germplasm resources had a highly diverse range of fruit quality, wide variation, and distribution. Insoluble tannin and soluble sugar were shown to have a substantial positive correlation with the sensory flavor indexes (p < 0.05), indicating their significance in influencing the flavor quality of persimmon fruit. Cluster analysis was performed utilizing 15 indexes of appearance, intrinsic quality, and 7 indexes of sensory quality. The samples were divided into two groups: group I consisted of 52 pollination−constant and astringent (PCA) and 1 pollination−-variant astringent (PVA) persimmon resources, and group II consisted of 6 pollination−constant non−astringent (PCNA) and 2 pollination−variant non−astringent (PVNA) persimmon resources. The results were consistent with the classification based on the mode of astringency loss, indicating that there was a significant difference in the quality of astringent and non−astringent persimmon fruit. This study provides theoretical references for the development and application of persimmon germplasm resources.

Catechins are essential phenolic compounds in persimmon. However, the catechin content in the leaves of persimmon germplasms has not been systematically and comprehensively evaluated. To systematically assess catechin variation in different growth stages and astringency types of persimmon leaves, the young and adult leaves catechin content of 249 persimmon germplasms from Korea, Japan, and 16 provinces in China was quantified using an HPLC method. The results showed that the content of (−)-epicatechin (EC) and (−)-gallocatechin gallate (GCG) had higher coefficient of variation (CV) values in persimmon young leaves (106.74%) and adult leaves (91.49%), respectively. The genetic diversity H’ of (+)-catechin (CA) and (+)-gallocatechin (GC) content was higher in young leaves (2.00 and 2.03), and the H’ value of (−)-epigallocatechin (EGC) and CA content was higher in adult leaves (1.98 and 1.92). The non-galloylated catechins, EGC, EC, and CA, were significantly positively correlated with each other in both young and adult leaves. Catechins of persimmon leaves showed different accumulation patterns in different growth stages and astringency types; (−)-epigallocatechin gallate (EGCG) and CA had the highest average content in the persimmon germplasms of Guangxi and Shanxi provinces of China, respectively. The content of (+)-catechin gallate (CG) was found to be significantly higher in Japanese pollination-constant non-astringent (J-PCNA) persimmon leaves, and EC, GCG had the highest levels in Chinese PCNA (C-PCNA) type. The 249 germplasms were classified into five clusters (Cluster I-V) by SOM clustering based on the content of nine catechins, with EC, CA, and GC having the highest content in Cluster V of the adult leaves. In addition, four excellent germplasms of Cluster III had the highest EGC and GC content in young leaves. Thus, the critical period for catechin utilization of persimmon leaves can be further determined, and provide theoretical references for excellent germplasm screening.

Pectins are major components of cell walls in plants. Pectin methylesterases (PMEs) and pectin methylesterase inhibitors (PMEIs) play crucial roles in pectin synthesis and metabolism. Overall, 28 putative DkPMEs and 29 putative DkPMEIs were identified from the D. kaki genome. According to phylogenetic analysis, DkPME/DkPMEI proteins can be classified into four and five clades, respectively. Motif and gene structure analysis showed that DkPME/DkPMEI are highly conserved in the same clades, which indicates that the function of these DkPME/DkPMEI were similar. Besides, DkPME/DkPMEI genes were distributed unevenly on their corresponding chromosomes. Synteny analysis showed that PME or PMEI gene usually matched with more than one DkPME/DkPMEI in D. oleifera, D. lotus, and A. thaliana, implying that the function of these genes in D. kaki may be diverse. Expression analysis showed that DkPME/DkPMEI from the same clade exhibited diverse expression patterns, indicating that these genes might have diverse functions. Functional protein–protein interaction network analysis showed that DkPMEI21 and DkPMEI15 were core nodes and were, respectively, positive and negative regulators for carbohydrate metabolism, stress responses, and sugar signaling. This study provides a theoretical basis for the functional characteristics, evolutionary relationship, and role of these gene families in developing persimmon fruit.