Mining Single Nucleotide Polymorphism (SNP) Markers for Accurate Genotype Identification and Diversity Analysis of Chinese Jujube (Ziziphus jujuba Mill.) Germplasm

Chinese jujube (Ziziphus jujuba Mill.) is an economically important fruit tree with outstanding adaptability to marginal lands and a broad range of climate conditions. There are over 800 cultivars, mostly landraces from China. However, a high rate of mislabeling in Chinese jujube germplasm restricts the sharing of information and materials among jujube researchers and hampers the use of jujube germplasm in breeding. In the present study, we developed a large panel of single nucleotide polymorphism (SNP) markers and validated 288 SNPs by genotyping 114 accessions of Chinese jujube germplasm. The validation resulted in the designation of a set of 192 polymorphic SNP markers that revealed a high rate of synonymous mislabeling in the jujube germplasm collection in Ningxia, China. A total of 17 groups of duplicates were detected, encompassing 49 of the 114 Chinese jujube cultivars. Model-based population stratification revealed two germplasm groups, and the core members of the two groups showed a significant genetic differentiation (Fst = 0.16). The results supported the hypothesis that the cultivated Chinese jujube had multiple origins and multiple regions of domestication. The Neighbor-Joining dendrogram further revealed that this collection is comprised of multiple sub-groups, each including 1-13 closely related cultivars. Parentage analysis of cultivars with known pedigree information proved the efficacy of using these SNP markers for parentage verification. A subset of 96 SNPs with high information index was selected for future downstream application including gene bank management, verification of pedigrees in breeding programs, quality control for propagation of planting materials and support of the traceability and authentication of jujube products.

Transcriptomic Analysis Reveals Key Candidate Genes Related to Seed Abortion in Chinese Jujube (Ziziphus jujuba Mill.)

Background: Seed abortion is a common phenomenon in Chinese jujube that seriously hinders the process of cross-breeding. However, the molecular mechanisms of seed abortion remain unclear in jujube. Methods: Here, we performed transcriptome sequencing using eight flower and fruit tissues at different developmental stages in Ziziphus jujuba Mill. ‘Zhongqiusucui’ to identify key genes related to seed abortion. Histological analysis revealed a critical developmental process of embryo abortion after fertilization. Results: Comparisons of gene expression revealed a total of 14,012 differentially expressed genes. Functional enrichment analyses of differentially expressed genes between various sample types uncovered several important biological processes, such as embryo development, cellular metabolism, and stress response, that were potentially involved in the regulation of seed abortion. Furthermore, gene co-expression network analysis revealed a suite of potential key genes related to ovule and seed development. We focused on three types of candidate genes, agamous subfamily genes, plant ATP-binding cassette subfamily G transporters, and metacaspase enzymes, and showed that the expression profiles of some members were associated with embryo abortion. Conclusions: This work generates a comprehensive gene expression data source for unraveling the molecular mechanisms of seed abortion and aids future cross-breeding efforts in jujube.

Composition and content of phenolic acids and flavonoids among the different varieties, development stages, and tissues of Chinese Jujube (Ziziphus jujuba Mill.)

The composition and content of phenolic acids and flavonoids among the different varieties, development stages, and tissues of Chinese jujube (Ziziphus jujuba Mill.) were systematically examined using ultra-high-performance liquid chromatography to provide a reference for the evaluation and selection of high-value resources. Five key results were identified: (1) Overall, 13 different phenolic acids and flavonoids were detected from among the 20 excellent jujube varieties tested, of which 12 were from the fruits, 11 from the leaves, and 10 from the stems. Seven phenolic acids and flavonoids, including (+)-catechin, rutin, quercetin, luteolin, spinosin, gallic acid, and chlorogenic acid, were detected in all tissues. (2) The total and individual phenolic acids and flavonoids contents significantly decreased during fruit development in Ziziphus jujuba cv.Hupingzao. (3) The total phenolic acids and flavonoids content was the highest in the leaves of Ziziphus jujuba cv.Hupingzao, followed by the stems and fruits with significant differences among the content of these tissues. The main composition of the tissues also differed, with quercetin and rutin present in the leaves; (+)-catechin and rutin in the stems; and (+)-catechin, epicatechin, and rutin in the fruits. (4) The total content of phenolic acid and flavonoid ranged from 359.38 to 1041.33 μg/g FW across all examined varieties, with Ziziphus jujuba cv.Jishanbanzao having the highest content, and (+)-catechin as the main composition in all 20 varieties, followed by epicatechin, rutin, and quercetin. (5) Principal component analysis showed that (+)-catechin, epicatechin, gallic acid, and rutin contributed to the first two principal components for each variety. Together, these findings will assist with varietal selection when developing phenolic acids and f lavonoids functional products.

Geographical and Varietal Traceability of Chinese Jujubes Based on Physical and Nutritional Characteristics

Chinese jujube fruits are known for their high nutritional and functional values. To protect advantageous regional jujube fruits, it is important to monitor quality indicators and trace the origin and variety. In this study, 31 quality indicators of Chinese jujubes collected from 6 main producing areas were determined. According to different origins and varieties, Chinese jujube fruits were divided into five and six categories, respectively. To simplify the parameters, eight of the main characteristics, namely, soluble sugar content, fresh mass, edible rate, Na, Mg, K, Zn, and cyclic adenosine monophosphate (cAMP), were screened based on multiple comparison, correlation analysis, and principal component analysis (PCA). According to the eight main parameters, it was found that that both the categorical and cross-validated classification accuracy of linear discriminant analysis (LDA) were 100%. The discrimination accuracy of the testing set samples based on the orthogonal partial least squares-discriminant analysis (OPLS-DA) model were 90 and 93% for geographical and varietal classification, respectively. This indicated that the eight main parameters could be used as the characteristic parameters for the origin and variety traceability of Chinese jujubes.

Review on Some Features of the Chinese Jujube (Ziziphus jujuba Mill.)

The Chinese jujube (Ziziphus jujuba Mill.), originating from China, with a history of over 4000 years, is one of the major fruit crops cultivated in China and on important areas in Central Asia, India, Iran, the Middle East etc. The high resistances to drought, salty soils and similar climate to that of China recommend this fruit tree as a valuable crop, especially in the context of climate changes and extended desertification. Chinese jujube has a high tolerance to pests and disease, being suitable for organic farming. The lack of divulgative papers on jujube true nutritional, medicinal and economic value, makes it still unknown for the great part of Romanian and European consumers, intensive advertising campaign is needed. The aim of this review is to highlight the requirements of the Chinese jujube (Ziziphus jujuba Mill.) in regards to the soil, water, climate as well as its high nutritional and medicinal values.