Jujube Cultivars Research Articles

Molecular Variation and Phylogeny of Thymidylate Kinase Genes of Candidatus Phytoplasma ziziphi from Different Resistant and Susceptible Jujube Cultivars in China

The thymidylate kinase (tmk) gene is indispensable for the proliferation and survival of phytoplasma. To reveal the molecular variation and phylogeny of the tmk genes of Candidatus phytoplasma ziziphi, in this study, the tmk genes of 50 phytoplasma strains infecting different resistant and susceptible jujube cultivars from different regions in China were amplified and analyzed. Two sequence types, tmk-x and tmk-y, were identified using clone-based sequencing. The JWB phytoplasma strains were classified into three types, type-X, type-Y, and type-XY, based on the sequencing chromatograms of the tmk genes. The type-X and type-Y strains contained only tmk-x and tmk-y genes, respectively. The type-XY strain contained both tmk-x and tmk-y genes. The type-X, type-Y, and type-XY strains comprised 42%, 12%, and 46% of all the strains, respectively. The type-X and type-XY strains were identified in both susceptible and resistant jujube cultivars, while type-Y strain was only identified in susceptible cultivars. Phylogenetic analysis indicated that the tmk genes of the phytoplasmas were divided into two categories: phylo-S and phylo-M. The phylo-S tmk gene was single-copied in the genome, with an evolutionary pattern similar to the 16S rRNA gene; the phylo-M tmk gene was multi-copied, related to PMU-mediated within-genome transposition and between-genome transfer. Furthermore, the phylogenetic tree suggested that the tmk genes shuttled between the genomes of the Paulownia witches’ broom phytoplasma and JWB phytoplasma. These findings provide insights into the evolutionary and adaptive mechanisms of phytoplasmas.

Study on the Metabolic Basis of the Color Formation of Two Color-Presenting Types of Jujube Fruits.

Jujube is a plant of the genus Ziziphus in the family Rhamnaceae; its fruit has high nutritional value, and it is rich in polyphenols, flavonoids, and other secondary metabolites. The color of its peel is an important indicator for evaluating the appearance of the fruit. However, the mechanism of the difference in color presentation between the seedling offspring of the 'Red Fruit' (TLHH) and the 'Green Fruit' (TLHL) of the fresh jujube cultivar 'Tailihong' is not clear. Therefore, this study used targeted metabolomics techniques to accurately and quantitatively analyze the metabolic pathways of carotenoid and anthocyanin metabolites during the ripening process of two color-presenting types of jujube fruits. Through the analysis of the dynamic changes in the pigment content of the jujube peel, it was found that 30 DAP (days after pollination), 80 DAP, and 110 DAP were the key periods for the development of the color of the peel of 'TLHL' and 'TLHH' jujube and that the substances responsible for the main differences were chlorophyll, carotenoids, and anthocyanins. Furthermore, we used an LC-MS/MS metabolic analysis to compare the differences in the carotenoids and anthocyanin metabolites between the two color-presenting types of jujube peels at the key periods of 30 DAP, 80 DAP, and 110 DAP. We detected 32 carotene metabolites and 75 anthocyanin metabolites, respectively, among which lutein had the highest content of carotenoids; it reached the maximum value (93.05 µg/g) and was higher than that of 'TLHH' (74.14 µg/g) at 30 DAP of 'TLHL'. Both showed a decreasing trend with fruit ripening. The anthocyanin with the highest content was cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, which reached the maximum value (258.32 µg/g) at 30 DAP of 'TLHH' and was 51.6 times that of 'TLHL'; similarly, both showed a decreasing trend with fruit ripening. These results elucidate the main metabolites of carotenoids and anthocyanins in the two types of jujube peel and their accumulation characteristics, suggesting that the key metabolites of the difference in color between 'TLHL' and 'TLHH' jujube fruits were lutein and cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, increasing the understanding of the color mechanism of jujube peel and providing a reference for targeted genetic breeding of jujube peel color.

Antioxidative enzymes, phytochemicals and proximate components in jujube fruit (Ziziphus mauritiana L.) with respect to genotypes and harvest maturity

Jujube is an underutilized fruit having high maturity variation at harvest. Investigations were made on eight different cultivars of jujube (Umran, Karela, Gurrh, Amrodia, Mehmood Wali, Aakash, Foladi and Khubani) for changes in antioxidative enzymatic activities, phytochemical functions and proximate composition with respect to different harvest maturity stages (M1: mature green, M2: yellow and M3: crispy brown) under postharvest ambient conditions (25 ± 2 °C; 60 %–65 % RH) at three shelf intervals (1, 3 and 5 d). Significant genotypic and maturity related variation was recorded regarding studied attributes. The fruit of cv. ʽKhubaniʼ had better attributes among the cultivars evaluated. The crispy brown jujube fruit had higher peroxidase (POD) and catalase (CAT) activity and more protein, total soluble solids (TSS), ash, crude fat and fiber than early mature stages. Over time, the ascorbic acid (vitamin C), titratable acidity (TA), total phenolic (TPC), total antioxidant capacity (TAC), crude protein, crude fiber, moisture, crude fat and activity of antioxidative enzymes [CAT and superoxide dismutase (SOD)] exhibited a significant decline; while increase was recorded in TSS, pH and POD activity. Overall, this work identified that jujube's antioxidative, biochemical and proximate properties are significantly influenced by cultivar, fruit harvest maturity and duration of postharvest handling under ambient shelf.

Genetic Diversity and Relationships among Indian Jujube (Ziziphus mauritiana Lamk.) Cultivars Using Morphometric Characteristics, matK Barcoding, and ISSR Markers

Indian jujube displays genetic diversity and does not prominently display minute morphometric variations, and this makes correct identification a difficult and long-term task. However, little work has been conducted to bring jujube cultivars into domestication. So, the present study aimed to evaluate eleven cultivars of Indian jujube in terms of the fruit’s morphometric characteristics, as well as molecular marker studies by plastidial megakaryocyte-associated tyrosine kinase (matK) barcoding and inter-simple sequence repeats (ISSR) markers for species differentiation, identification, and relationships among Indian jujube cultivars. The results of the morphometric characteristics showed that the mean geometric diameter, surface area, sphericity, sphericity ratio, shape index, fruit length, fruit diameter, fruit weight, and seed weight varied among cultivars. The results also showed that the color values of L*, a*, and b* for fruits differed in different cultivars. In addition, the results showed a discrepancy in the genetic diversity parameters related to the matK barcoding, ISSR markers, and relationships among Indian jujube cultivars. Substantially, hierarchical clustering by heatmap revealed that ‘Zytoni’ and ‘Um-Sulaem’ with spines seem to be mono-clades distinct from other cultivars, which related to variations in the expression levels of genes. Therefore, they should be relied upon together to distinguish and identify cultivars in order to maximize the effectiveness of local germplasm conservation and exploitation.

Characterization based on colorimetry, physiology and sensory attributes among traditional jujube cultivars of Sindh, Pakistan

Jujube (Ziziphus spp.) fruit is attaining incredible attention in current global climatic changing scenario as the fruit has significant nutritional value but remained unexplored in past. Fifteen Jujube cultivars were selected at Jujube Research Station Tandojam, Sindh Pakistan, to exploit their morphological, physiochemical, color and sensory attributes. Measured traits like tee shape diverged as semi erect, erect and spreading whereas leaf shape was also found highly variable. Thorn attachment differed as cadoucous, partial and persistent and fruit shape was set as round, oblong, oval and ovate. Maximum leaf blade length was counted by Soofi sanghar (9.0cm) while lowest was found in Gola soghat (5.1cm). Maximum fruit mass was recorded in cultivar Late gola (31.57 g) whereas least was observed in Khirol mukkhri (5.63 g). Maximum stone weight was estimated in Early gola (10.55 g) whereas minimum was recorded in Khirol desi (6.4 g). Highest glucose level was observed in Soofi local (4.46 g 100 mL−1) while lowest glucose level was recorded in Khirol desi and Khirol Ratam (3.53g 100 mL−1). Best cultivars by appearance were Late gola and Early gola followed by Gola saffina, Gola soghat, Soofi sanghar and Soofi local. Findings of this study are useful for varietal improvement and to run successful breeding programmes. Commercially relevant features evaluated in this study are highly beneficial for jujube varietal identification and germplasm conservation

The Flavor Characteristics and Metabolites of Three Commercial Dried Jujube Cultivars.

To understand the flavor and metabolite differences between the three commercial dried jujube cultivars Huizao (HZ), Hamazao 1 (HMZ), and Qiyuexian (QYX), their soluble sugars, organic acids, volatiles, and metabolites were systematically investigated. The results show that sucrose and malic acid were the main soluble sugar and organic acids contained in these dried jujubes, respectively. Sucrose (573.89 mg/g DW) had the highest presence in HZ, and the total sugar content (898.33 mg/g DW) was the highest in QYX. Both of these had a low total acid content, resulting in relatively high sugar-acid ratios (105.49 and 127.86, respectively) compared to that of HMZ (51.50). Additionally, 66 volatile components were detected in the 3 jujubes. These mainly included acids, aldehydes, esters, and ketones (90.5-96.49%). Among them, (E)-2-nonenal, (E)-2-decenal, heptanal, decanal, nonanal, and octanal were identified as the key aromatic substances of the dried jujubes, and their contents were the highest in HMZ. Moreover, 454 metabolites were identified, including alkaloids, amino acids, flavonoids, lipids, nucleotides, and terpenoids. The highest contents of flavonoids (5.6%) and lipids (24.9%) were detected in HMZ, the highest contents of nucleotides (10.2%) and alkaloids (27%) were found in QYX, and the contents of saccharides (5.7%) and amino acids (23.6%) were high in HZ. Overall, HZ, HMZ, and QYX significantly differ in their flavor and nutrition. HZ tastes better, HMZ is more fragrant, and QYX and HMZ possess higher nutritional values.

Analysis of endogenous benzoic acid content in different jujube varieties, maturity stages, and processing types: Implications for the agri-food industry

AbstractBenzoic acid naturally exists in a variety of plants and fermented foods, and jujube contains natural benzoic acid. This study scrutinises the content of benzoic acid in diverse jujube cultivars, and its modulation by variables such as harvest timing, product types, and drying techniques. The methodology encompasses tracking the progressive augmentation of benzoic acid throughout the maturation process of jujube, with the apex content being 144.4 mg kg−1 in the Junzao cultivar. It further investigates the substantial fluctuations in benzoic acid content in jujube powder under disparate processing conditions, with the zenith content observed in drum-dried jujube powder at 127.6 mg kg−1, and an unexpectedly elevated level of 66.2 mg kg−1 in freeze-dried jujube powder. As long as it is not consumed excessively, it will not cause harm to the human body. The conclusion drawn from this research posits can be employed to resolve consumer grievances, or as a benchmark for testing services for product quality control.

Genetic Diversity and Population Structure of Jujube Cultivars in the United States Revealed by Single Nucleotide Polymorphism Markers

The nutritional and medicinal significance of jujube (Ziziphus jujuba) has led to persistent efforts in genomics to accelerate the utilization of its germplasm resources. However, the absence of accurate genetic identity of existing germplasm limits these studies. In the United States, different names were frequently given to the same jujube cultivars because the pedigrees of the imported germplasm are unclear. The present study selected a panel of 147 single nucleotide polymorphism (SNP) markers distributed across the jujube genome to examine genetic identity, genetic diversity, and population structure in 177 jujube cultivars sampled from different locations in the United States. SNP profile multilocus matching reported a total of 23 synonymous groups including 116 samples that were identical to at least one other sample. This led to the detection of 74 unique genotypes for subsequent diversity analysis. Model-based genetic structure analysis divided the distinctive genotypes into three major groups, with some admixtures among the groups. The genetic differentiation among these groups was further validated by analysis of molecular variance (Fst = 0.199, P value < 0.001), principal coordinate analysis, and clustering analysis. Morphological traits were studied in some of the genetically identical commercial cultivar groups, (i.e., Li, Lang, and Jinsi). Results demonstrated significant morphological differences within genetically identical cultivars in the Jinsi group, indicating phenotypic variation resulting from mutations in these clones.

Comparative analysis of 326 chloroplast genomes in Chinese jujube (Ziziphus jujuba): Structural variations, horizontal gene transfer events, and evolutionary patterns impacting its domestication from wild jujube

AbstractJujube (Ziziphus jujuba Mill.), renowned for its nutritional value and health benefits, is believed to have originated in the middle and lower reaches of the Yellow River in China, where it underwent domestication from wild jujube. Nonetheless, the evolutionary trajectory and species differentiation between wild jujube and cultivated jujube still require further elucidation. The chloroplast genome (plastome), characterized by its relatively lower mutation rate compared to the nuclear genome, serves as an excellent model for evolutionary and comparative genomic research. In this study, we analyzed 326 nonredundant plastomes, encompassing 133 jujube cultivars and 193 wild jujube genotypes distributed throughout China. Noteworthy variations in the large single copy region primarily account for the size differences among these plastomes, impacting the evolution from wild jujube to cultivated varieties. Horizontal gene transfer (HGT) unveiled a unique chloroplast‐to‐nucleus transfer event, with transferred fragments predominantly influencing the evolution of the nuclear genome while leaving the plastome relatively unaffected. Population genetics analysis revealed two distinct evolutionary pathways from wild jujube to cultivated jujube: one driven by natural selection with minimal human interference, and the other resulting from human domestication and cultivation. Molecular dating, based on phylogenetic analysis, supported the likelihood that wild jujube and cultivated jujube fall within the same taxonomic category, Z. jujuba. In summary, our study comprehensively examined jujube plastome structures and HGT events, simultaneously contributing novel insights into the intricate processes that govern the evolution and domestication of jujube species.

The Influences of Soil and Meteorological Factors on the Growth and Fruit Quality of Chinese Jujube (Ziziphus jujuba Mill.).

Chinese jujube (Ziziphus jujuba Mill.) is attracting more and more attention worldwide due to their tasty and nutritious fruit with extremely high contents of vitamin C (Vc) and soluble sugar. In order to find out the main factors that influence jujube growth and reproductive adaptability, the phenological periods, vegetative growths, fruiting abilities, and fruit qualities of eight newly released cultivars were compared and comprehensively analyzed in three representative ecological sites of the three main jujube-producing regions including Fuping (Hebei), Taigu (Shanxi), and Alar (Xinjiang) in China. Our results showed that the characteristics of jujube cultivars were significantly affected by soil and meteorological factors. The fruit number per bearing shoot was much more affected by temperature, light, and rainfall. The fruit number per bearing shoot, contents of soluble solids, and soluble sugar and Vc contents in fruits were influenced more by meteorological factors. The content of flavonoids was affected by both soil and meteorological factors. A principal component analysis (PCA) indicated that cultivars suitable for planting in Fuping (Hebei) were Yuhong and Lengbaiyu. Zaocuimi, Fucuimi, and Zaoqiuhong were suitable to be cultivated in Taigu (Shanxi), while Zaocuimi, Yuhong, Yulu, Luzao 2, and Yueguang behaved better in Alar (Xinjiang). This study provides insights of the environmental factors on jujube yield and quality and therefore provides references for highly efficient jujube cultivation.

Physicochemical properties and antioxidant activity of Yulingdang jujube (Ziziphus jujuba Mill.) fruit at different stages of maturity

ABSTRACT Ziziphus jujuba cv. Yulingdang (YLD) is a jujube cultivar that has been approved as a new plant cultivar by the State Forestry Administration of China. The physicochemical properties and antioxidant activity of YLD fruit were evaluated at seven stages of maturation, ranging from fruit setting to red ripe. The antioxidant activity of YLD fruit was assessed through total phenolics, total flavonoids, and methods including the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging rate, β-carotene-linoleic acid emulsification method, and reducing power. These measures were observed to decrease gradually as maturation progressed. The study also indicated an increase in total sugar and total acid levels, along with a decrease in moisture, soluble protein, and the sugar-acid ratio during maturation. Understanding this information is essential to fully exploit the commercial potential of YLD fruit.

Multiple-Genome-Based Simple Sequence Repeat Is an Efficient and Successful Method in Genotyping and Classifying Different Jujube Germplasm Resources.

Jujube (Ziziphus jujuba Mill.) is a commercially important tree native to China, known for its high nutritional value and widespread distribution, as well as its diverse germplasm resources. Being resilient to harsh climatic conditions, the cultivation of jujube could provide a solution to food insecurity and income for people of arid and semi-arid regions in and outside of China. The evaluation of germplasm resources and genetic diversity in jujube necessitates the use of Simple Sequence Repeat (SSR) markers. SSR markers are highly polymorphic and can be used to evaluate the genetic diversity within and between cultivars of Chinese jujube, and are important for conservation biology, breeding programs, and the discovery of important traits for Chinese jujube improvement in China and abroad. However, traditional methods of SSR development are time-consuming and inadequate to meet the growing research demands. To address this issue, we developed a novel approach called Multiple-Genome-Based SSR identification (MGB-SSR), which utilizes the genomes of three jujube cultivars to rapidly screen for polymorphic SSRs in the jujube genome. Through the screening process, we identified 12 pairs of SSR primers, which were then used to successfully classify 249 jujube genotypes. Based on the genotyping results, a digital ID card was established, enabling the complete identification of all 249 jujube plants. The MGB-SSR approach proved efficient in rapidly detecting polymorphic SSRs within the jujube genome. Notably, this study represents the first successful differentiation of jujube germplasm resources using 12 SSR markers, with 4 markers successfully identifying triploid jujube genotypes. These findings offer valuable information for the classification of Chinese jujube germplasm, thereby providing significant assistance to jujube researchers and breeders in identifying unknown jujube germplasm.

Construction of a High-Density Genetic Linkage Map Based on Bin Markers and Mapping of QTLs Associated with Fruit Size in Jujube (Ziziphus jujuba Mill.)

Jujube (Ziziphus jujuba Mill.) is a fruit tree that is gaining increasing importance in drought-affected regions worldwide. The fruit size is an important quantitative agronomic trait that affects not only the fruit yield and attractiveness but also consumer preference. Genetic enhancement of fruit appearance is a fundamental goal of jujube breeding programs. The genetic control of jujube fruit size traits is highly quantitative, and development of high-density genetic maps can facilitate fine mapping of quantitative trait loci (QTLs) and gene identification. However, studies regarding the construction of high-density molecular linkage maps and identification of quantitative trait loci (QTLs) targeting fruit size in jujube are limited. In this study, we performed whole-genome resequencing of the jujube cultivars “JMS2” and “Xing16” and their 165 F1 progenies to identify genome-wide single-nucleotide polymorphism (SNP) markers and constructed a high-density bin map of jujube that can be used to assist in the selection of multiple traits in jujube breeding. This analysis yielded a total of 116,312 SNPs and a genetic bin map of 2398 bin markers spanning 1074.33 cM with an average adjacent interval of 0.45 cM. A quantitative genetic analysis identified 15 QTLs related to fruit size and the observed phenotypic variation associated with a single QTL ranged from 9.5 to 13.3%. Through the screening of overlapping and stable QTL regions, we identified 113 candidate genes related to fruit size. These genes were ascertained to be involved in cell division, cell wall metabolism, synthesis of phytohormones (ABA, IAA, and auxin), and encoding of enzymes and transcription factors. These candidate genomic regions will facilitate marker-assisted breeding of fruits with different sizes and shapes and lay a foundation for future breeding and manipulation of fruit size and shape in jujube.

Jujube Fruit Metabolomic Profiles Reveal Cultivar Differences and Function as Cultivar Fingerprints.

Jujube is a nutritious fruit, and is high in vitamin C, fiber, phenolics, flavonoids, nucleotides, and organic acids. It is both an important food and a source of traditional medicine. Metabolomics can reveal metabolic differences between Ziziphus jujuba fruits from different jujube cultivars and growth sites. In the fall of 2022, mature fresh fruit of eleven cultivars from replicated trials at three sites in New Mexico-Leyendecker, Los Lunas, and Alcalde-were sampled from September to October for an untargeted metabolomics study. The 11 cultivars were Alcalde 1, Dongzao, Jinsi (JS), Jinkuiwang (JKW), Jixin, Kongfucui (KFC), Lang, Li, Maya, Shanxi Li, and Zaocuiwang (ZCW). Based on the LC-MS/MS analysis, there were 1315 compounds detected with amino acids and derivatives (20.15%) and flavonoids (15.44%) as dominant categories. The results reveal that the cultivar was the dominant factor in metabolite profiles, while the location was secondary. A pairwise comparison of cultivar metabolomes revealed that two pairs had fewer differential metabolites (i.e., Li/Shanxi Li and JS/JKW) than all the other pairs, highlighting that pairwise metabolic comparison can be applied for cultivar fingerprinting. Differential metabolite analysis also showed that half of drying cultivars have up-regulated lipid metabolites compared to fresh or multi-purpose fruit cultivars and that specialized metabolites vary significantly between cultivars from 35.3% (Dongzao/ZCW) to 56.7% (Jixin/KFC). An exemplary analyte matching sedative cyclopeptide alkaloid sanjoinine A was only detected in the Jinsi and Jinkuiwang cultivars. Overall, our metabolic analysis of the jujube cultivar's mature fruits provides the largest resource of jujube fruit metabolomes to date and will inform cultivar selection for nutritional and medicinal research and for fruit metabolic breeding.

Analysis of Metabolites and Metabolic Pathways of Three Chinese Jujube Cultivar.

Most studies on metabolites in jujube fruits focus on specific types of metabolites, but there are only a few comprehensive reports on the metabolites in jujube fruits. In order to understand the variance of metabolites in fruits of different jujube varieties. The objective of this study was to explore the metabolic components of jujube fruit by comparing three cultivars, namely Linyi LiZao (LZ), Jiaocheng SuantianZao (STZ), and Xianxian Muzao (MZ). The metabolites present in the fruits of these three cultivars were evaluated and compared. The results revealed the detection of 1059 metabolites across the three jujube varieties, with each cultivar exhibiting distinct metabolic characteristics. Notably, MZ exhibited a higher abundance of six metabolite classes, namely amino acids and derivatives, flavonoids, lipids, organic acids, phenolic acids, and terpenoids, compared to LZ. Conversely, LZ exhibited higher concentrations of alkaloids, lignans, coumarins, nucleotides, and their derivatives compared to the other two cultivars. In terms of STZ, its content of amino acids and derivatives, lignans and coumarins, organic acids, and phenolic acids was largely similar to that of LZ. However, the content of alkaloids, nucleotides, and their derivatives, and terpenoids was significantly higher in STZ compared to LZ. Additionally, STZ exhibited lower levels of flavonoids and lipids compared to LZ. Moreover, MZ was found to be less nutritionally rich than STZ, except for lignans and coumarins, as it displayed lower levels of all the metabolites. KEGG pathway enrichment analysis revealed six significantly different metabolic pathways (p < 0.05) between LZ and MZ, including arginine and proline metabolism, sphingolipid metabolism, flavonoid biosynthesis, glutathione metabolism, glycerophospholipid metabolism, and cysteine and methionine metabolism. The metabolites in STZ and MZ exhibited three significantly different pathways (p < 0.05), primarily associated with flavonoid biosynthesis, arginine and proline metabolism, and sphingolipid metabolism. The significantly differential metabolites between LZ and STZ were observed in the phenylpropionic acid biosynthesis pathway and the ubiquinone and other terpenoid-quinone biosynthesis pathways. LZ showed a closer relationship with STZ than with MZ. STZ and LZ exhibited higher medicinal values, while LZ had lower acidity and MZ displayed better antioxidant activity. This study presents the first thorough analysis of metabolites in LZ, STZ, and MZ cultivars, which can serve as a theoretical basis for quality analysis, functional research, and classification processing of jujube fruit.

The Key Metabolic Network and Genes Regulating the Fresh Fruit Texture of Jujube (Ziziphus jujuba Mill.) Revealed via Metabolomic and Transcriptomic Analysis.

The texture of fresh jujube fruit is related to its popularity and commercial value. The metabolic networks and essential genes that regulate the texture of jujube (Ziziphus jujuba) fruit are still unknown. In this study, two jujube cultivars with significantly different textures were selected by a texture analyzer. The four developmental stages of the exocarp and mesocarp of jujube fruit were studied separately using metabolomic and transcriptomic analyses. Differentially accumulated metabolites were enriched in several critical pathways related to cell wall substance synthesis and metabolism. Transcriptome analysis confirmed this by finding enriched differential expression genes in these pathways. Combined analysis showed that 'Galactose metabolism' was the most overlapping pathway in two omics. Genes such as β-Gal, MYB and DOF may affect fruit texture by regulating cell wall substances. Overall, this study provides an essential reference for the establishment of texture-related metabolic and gene networks of jujube fruit.

Composition Analysis and Nutritional Value Evaluation of Amino Acids in the Fruit of 161 Jujube Cultivars.

Amino acids are an essential group of compounds involved in protein synthesis and various metabolic and immune reactions in the human body. Chinese jujubes (Ziziphus jujuba Mill.) are an important fruit and medicinal plant which are native to China and have been introduced into around 50 countries. However, systematic research on the composition and content diversity of amino acids in the jujube is still lacking. In this experiment, the amino acid composition and the contents of the dominant amino acids in the fruit of 161 cultivars of jujube were determined by HPLC. Of the twenty-one kinds of amino acids detected, a total of fourteen kinds of amino acids were detected, of which eight kinds of amino acids were relatively high, including five essential amino acids (threonine, valine, isoleucine, leucine, and phenylalanine) and three nonessential amino acids (glycine, alanine, and proline). However, the contents of the remaining six amino acids were relatively low (aspartic acid, glutamic acid, histidine, serine, arginine, and tryptophan). Therefore, the eight primary amino acids were used as the index to evaluate the amino acids of 161 jujube varieties. Proline accounts for 56.8% of the total amino acid content among the eight amino acids. The total content of the eight primary amino acids in most jujube varieties was 1-1.5 g/100 g, and the highest content of 'Zaoqiangmalianzao' was 2.356 g/100 g. The average content of proline was 6.01-14.84 times that of the other seven amino acids. According to the WHO/FAO revised model spectrum of ideal essential amino acids for humans, 19 cultivars met the E/T (essential amino acids/total amino acids) standard, and their values ranged from 35% to 45%; 12 cultivars meet E/NE (non-essential amino acids) ≥ 60%. All cultivars reached the requirement of BC (branched-chain amino acids)/E ≥ 40% with 15 cultivars over 68%. One hundred and fifty-seven cultivars reach the standard of BC/A (aromatic amino acids) ≈ 3.0~3.5. The amino acid ratio coefficient analysis showed that phenylalanine was the first limiting amino acid of all the jujube cultivars. The SRC (the score of amino acid ratio coefficient) values of 134 cultivars were between 50% and 70%, with 12 cultivars over 70%, indicating that jujube fruits are of high nutritional value in terms of amino acids. Based on the principal component analysis and comprehensive ranking of amino acid nutritional value, the top five cultivars were screened from the 161 ones tested, i.e., 'Tengzhouchanghongzao', 'Xinzhengxiaoyuanzao', 'Hanguowudeng', 'Xuputiansuanzao', and 'Lichengxiaozao'. This study established, firstly, a complete basic data analysis of amino acid content in jujube fruit which could be used to select germplasm resources suitable for developing functional amino acid food, and provide theoretical support for the high value utilization of amino acids in jujubes.

Transcriptome and weighted gene co-expression network analysis of jujube (Ziziphus jujuba Mill.) fruit reveal putative genes involved in proanthocyanin biosynthesis and regulation

Proanthocyanidin (PA) is an important bioactive compound with multiple physiological benefits in jujube (Ziziphus jujube Mill.). However, the molecular mechanisms underlying PA biosynthesis in jujube fruit have not been investigated. Here, the profiling of PA, (+)-catechin and (–)-epicatechin and transcriptome sequencing of three jujube cultivars from Xinjiang Uyghur Autonomous Region of China at five developmental stages were analyzed. The levels of total PAs and catechin exhibited a decreased trend over jujube ripening, and epicatechin content of two jujube cultivars increased first and then declined. Transcriptome analysis revealed that the differentially expressed genes (DEGs) were mainly enriched in ribosome, glycolysis/gluconeogenesis, fructose and mannose metabolism. 17 DEGs encoding PAL, CHS, CHI, CHS, F3’H, LAR, ANR, C4Hs, 4CLs, FLSs, DFRs and UFGTs involved in PA biosynthesis were relatively abundant. The highly transcribed LAR gene may greatly contribute to epicatechin accumulation. A weighted gene co-expression network analysis (WGCNA) was performed, and a network module including 1620 genes highly correlated with content of Pas and catechin was established. We identified 58 genes including 9 structural genes and 49 regulatory genes related to PA biosynthesis and regulation in the WGCNA module. Sixteen genes encoding 9 families of transcriptional factors (i.e., MYB, bHLH, ERF, bZIP, NAC, SBP, MIKC, HB, WRKY) were considered as hub genes. The results of qRT-PCR analysis validating 10 genes were well consistent with the transcriptome data. These findings provide valuable knowledge to facilitate its genetic studies and molecular breeding.

Dynamics of Nutrients in Jujube (Ziziphus jujuba Mill.) at Different Maturity Stages, Cultivars, and Locations in the Southwest United States

Jujube (Ziziphus jujuba Mill.) is also called Chinese date. There are ∼100 jujube cultivars with limited commercial availability, and the majority of them have scant details in the United States. In this study, nutrient dynamics during fruit maturation of different jujube cultivars grown at Las Cruces, Los Lunas, and Alcalde, NM, were examined in 2018 and 2019. Cultivars varied by location and year, and included ‘Li’, ‘Lang’, ‘Sugarcane’, ‘September Late’, and ‘Sherwood’. Parameters tested were total phenolic content (TPC), proanthocyanidins (PAs), vitamin C, cyclic adenosine monophosphate (cAMP), and antioxidant capacity: 2,2-diphenylpicrylhydrazyl radical scavenging capacity and ferric reducing antioxidant potential (FRAP). Moisture, TPC, PAs, FRAP, and vitamin C content decreased with fruit maturity; however, the latter stage of fruit maturity showed an increase in cAMP. Compared with fruit at full-red maturity, creamy fruit had TPC, PA, FRAP, and vitamin C concentrations that were 1.0 to 1.8, 4.4 to 12.4, 1.9 to 2.6, and 0.1 to 1.3 times higher, respectively, depending on location (P &lt; 0.05). From creamy to full-red maturity, cAMP increased by 0.9 to 4.5 times. At full-red maturity, estimated TPC in jujube fruit ranged from 10.6 to 16.8 mg gallic acid equivalent per gram dry weight (DW), whereas estimated PAs ranged from 1.8 to 5.3 mg PA B2/g DW. Jujube fruit at full-red maturity had a vitamin C content that ranged from 649.0 to 1153.3 mg/100 g DW. At full-red maturity, the concentration of cAMP ranged from 148.1 to 277.6 μg/g DW in Las Cruces samples.

Transcriptome sequencing reveals potential key genes of cellular changes during the first rapid growth stage of jujube fruit size

ABSTRACT Cell number and size are essential factors in determining the final size of the fruit. However, studies on the cellular changes and molecular mechanisms of jujube fruit size development are still unclear. In this study, changes in fruit length, width, weight, and corresponding mesocarp cells were measured during jujube fruit development. The results showed that cell division and cell expansion jointly participated in the first rapid growth stage of fruit size, and cell expansion was the main factor in the second rapid growth stage of fruit size. In a further study, transcriptome sequencing was used to analyse the expression profile of fruit size's first rapid growth stage. Most of these DEGs were assigned to seven significant trends. Three genes related to the auxin signal transduction pathway and three genes related to the brassinosteroid biosynthesis signal transduction pathway were detected to be directly related to cell enlargement and cell division, respectively, which may regulate the first rapid growth of fruit size. In conclusion, candidate genes were provided for regulating fruit size in this study, which is beneficial for analysing the molecular mechanism of fruit size and lays a foundation for breeding large-fruit jujube cultivars.