Assessment of Fruit Quality and Genes Related to Proanthocyanidins Biosynthesis and Stress Resistance in Persimmon (<i>Diospyros kaki</i> Thunb.)

Persimmon (Diospyros kaki Thunb.) is becoming a fruit that is used worldwide because it contains high nutritional and medicinal value. However, the trait evaluation of persimmon is still needed and is critical for marketing and breeding, especially in China. Here, we evaluated thirteen quality indicators (fruit weight, horizontal length, vertical length, firmness, titratable acid content, vitamin C content, flavonoid content, anthocyanin content, soluble sugar content, pectinase activity, soluble protein content, tannin content, and tannin cell size) in six Chinese pollination-constant, astringent (PCA) persimmon cultivars (‘Jinxi 3′, ‘Ganfang 1′, ‘Poyang 5′, ‘Poyang 6′, ‘Yifeng 1′, and ‘Yifeng 3′) and a Japanese pollination-constant non-astringent (PCNA) persimmon cultivar (‘Youhou’). The quality indicator data were normalized and subjected to variant analysis and principal component analysis (PCA). The results showed that 10 of 13 indicators among the seven persimmon cultivars were significantly different, and the contribution rates of the first principal component reached 40.582%. The principal component comprehensive scores for ‘Poyang 5′ and ‘Ganfang 1′ ranked second and third, respectively, and were clustered with that of ‘Youhou.’ In addition, we also measured the expression levels of three stress resistance genes and three proanthocyanidin (PA, also called condensed tannins) pathway genes in these persimmon cultivars by quantitative reverse transcription PCR (qRT—PCR). The qRT—PCR analysis of DkCBF and DkWRKY3/8 showed low resistance to cold in ‘Ganfang 1′ but stronger resistance to anthracnose. Moreover, the expression of the PA pathway genes demonstrated that the PA content in ‘Ganfang 1′ was at a moderate level in the seven varieties. Together, our study revealed relatively comprehensive profiles of persimmon quality evaluation and demonstrated that ‘Ganfang 1′ may have the potential to be used as a breeding parent for future persimmon breeding programs