De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit ...
De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit ...
De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes
More Information-
Abstract
Stenocereus thurberi is a cactus endemic to the Sonoran desert (Mexico), which produces a fruit named sweet pitaya. One trait that allows the cactus to survive in desert ecosystems is its cuticle, which limits water loss in dry conditions. Nevertheless, the mechanism of cuticle biosynthesis has yet to be described for cactus fruits. Also, transcripts from S. thurberi published in the databases are scarce. This study reports the de novo assembly of the sweet pitaya peel transcriptome. The assembly includes 174,449 transcripts with an N50 value of 2,110 bp. Out of the total transcripts, 43,391 were classified as long non-coding RNA. Functional categorization analysis suggests that mechanisms of response to stress and cuticle biosynthesis are carried out in fruit pitaya peel. The transcripts coding for a cytochrome p450 77A (StCYP77A), Gly-Asp-Ser-Leu motif lipase/esterase 1 (StGDSL1), and ATP binding cassette G 11 (StABCG11), which carried out the synthesis, polymerization, and transport of cuticle components, respectively, were identified. Expression analysis during fruit development suggests an active cuticle biosynthesis at the early stages and the ripe stages, carried out by StCYP77A, StGDSL1, and StABCG11. The dataset generated here will help to improve the elucidation of the molecular mechanism of cuticle biosynthesis in S. thurberi and other cactus fruits.-
Keywords:
- Peel,
- Transcriptome,
- Stenocereus thurberi,
- Fruit,
- Development
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Supplementary information
Supplementary File 1 Nucleotide a nd p redicted a mino a cid s equences o f t he cuticle biosynthesis-related transcripts. Supplementary Table S1 Summary of homology search for sweet pitaya (Stenocereus thurberi) transcripts in different databases. Homologous sequences were predicted by an alignment through BLAST21 to the protein databases listed in the table with an E value threshold of < 1 × 10−10 for the nr-NCBI database and an E value threshold of < 1 × 10−5 for the others. Supplementary Table S2 Homology search for sweet pitaya (Stenocereus thurberi) transcripts in commercial fruits and other cactus. Homologous sequences were predicted by an alignment through BLAST21 to the protein databases listed in the table with an E value threshold of < 1 × 10−5. Supplementary Table S3 Nucleotide and amino acid sequences of characterized cuticle biosynthesis genes from model plants. Supplementary Table S4 List of proteins from Arabidopsis (subject) homologous to sweet pitaya transcripts (query). BLASTx alignment against the TAIR database with an E value < 1×10−5. Only the results of the thirteen bi-directional homologous transcripts here analyzed are shown. Supplementary Table S5 List of proteins from tomato (subject) homologous to sweet pitaya transcripts (query). BLASTx alignment against the ITAG database with an E value < 1 × 10−5. Only the results of the thirteen bi-directional homologous transcripts here analyzed are shown. Supplementary Table S6 List of predicted proteins from sweet pitaya (subject) homologous to cuticle biosynthesis genes from model plants (query). BLASTx alignment against the sweet pitaya predicted proteins with an E value < 1 × 10−5. Supplementary Table S7 List of predicted proteins from sweet pitaya (subject) homologous to cuticle biosynthesis proteins from model plants (query). BLASTp alignment against the sweet pitaya predicted proteins with an E value < 1 × 10−5. Supplementary Table S8 List of transcripts from sweet pitaya (subject) homologous to cuticle biosynthesis proteins from model plants (query). tBLASTn alignment against the sweet pitaya transcriptome with an E value < 1×10-5. Supplementary Table S9 List of transcription factors homologous to sweet pitaya transcripts. BLASTx alignment against the PlantTFDB with a E value < 1 × 10−5. Supplementary Table S10 List of protein kinases homologous to sweet pitaya transcripts. BLASTx alignment with a E value < 1 × 10−5. Supplementary Table S11 List of transcriptional regulators homologous to sweet pitaya transcripts. BLASTx alignment with a E value < 1 × 10−5. Supplementary Table S12 Gene Ontology (GO) terms and Enzyme Codes (EC) assigned to the sweet pitaya peel transcripts. Supplementary Table S13 Top20 of Gene Ontology (GO) terms assigned to the sweet pitaya peel transcripts. Supplementary Table S14 Metabolic pathways from the KEGG database assigned to the sweet pitaya peel transcripts. Supplementary Table S15 Length of coding and long non-coding transcripts from sweet pitaya peel. Supplementary Table S16 Abundance of coding and long non-coding transcripts from sweet pitaya peel. Supplementary Table S17 Differential expression analysis results between M1 and M2 libraries. FC: Fold Change, CPM: Counts per million of reads, FDR: False Discovery Rate. Supplementary Table S18 Differential expression analysis results between M1 and M3 libraries. FC: Fold Change, CPM: Counts per million of reads, FDR: False Discovery Rate. Supplementary Table S19 Differential expression analysis results between M1 and M4 libraries. FC: Fold Change, CPM: Counts per million of reads, FDR: False Discovery Rate. Supplementary Table S20 Expression data of the not differentially expressed transcripts (log2FC < 1, FDR < 0.05). Supplementary Table S21 Expression data of the 27 tentative reference genes with the lowest coefficient of variation (< 0.113). Supplementary Table S22 Expression data and coefficient of variation of the 14 sweet pitaya transcripts homologous to reference genes from other cactus fruits. Supplementary Table S23 Homology of the candidate reference genes and the cuticle biosynthesis-related transcripts from Stenocereus thurberi. The homologous search was carried out through BLAST alignment of the S. thurberi transcriptome to Hylocereus polyrhizus transcripts, TAIR, ITAG, and SwissProt database using a maximal E value of 1×10−5. Abbreviations: Actin 7 (StACT7), alpha-tubulin (StTUA), elongation factor 1-alpha (StEF1a), COP1-interactive protein 1 (StCIP1), plasma membrane ATPase 4 (StPMA4), BEL1-like homeodomain protein 1 (StBLH1), polyubiquitin 3 (StUBQ3), plastidic ATP/ADP-transporter (StTLC1), cytochrome p450 family 77 subfamily A (StCYP77A), Gly-Asp-Ser-Leu motif lipase/esterase 1 (StGDSL1), and ATP binding cassette transporter family G member 11 (StABCG11). S. thurberi transcripts identified in this study were designated with the prefix "St" and the name of their best homologous match from other plant species. Supplementary Table S24 Oligonucleotide sequences designed to amplify the candidate reference genes and transcripts involved in cuticle biosynthesis. Primers were designed with the PrimerQuest, OligoAnalyzer, and UNAFold tools from Integrated DNA Technologies (www.idtdna.com). Abbreviations: Primer melting temperature (Tm), base pairs (bp), plastidic ATP/ADPtransporter (StTLC1), plasma membrane ATPase 4 (StPMA4), polyubiquitin 3 (StUBQ3), alpha-tubulin (StTUA), actin 7 (StACT7), elongation factor 1-alpha (StEF1a), COP1-interactive protein 1 (StCIP1), ATP binding cassette transporter family G member 11 (StABCG11), BEL1-like homeodomain protein 1 (StBLH1), Gly-Asp-Ser-Leu motif lipase/esterase 1 (StGDSL1), and cytochrome p450 family 77 subfamily A (StCYP77A). S. thurberi transcripts identified in this study were designated with the prefix "St" and the name of their best homologous match from other plant species. Supplementary Table S25 Nucleotide sequences of the candidate reference genes. Supplementary Table S26 Cycle threshold (Ct) values of the tentative reference genes during sweet pitaya fruit development. Supplementary Table S27 Stability analysis of the candidate reference genes during sweet pitaya fruit development. The values were calculated by the algorithms geNorm (M value), NormFinder (stability value), BestKeeper (standard deviation +/− crossing point value), the deltaCt method (average of standard deviation), and RefFinder (geometric mean of ranking values) from the cycle threshold (Ct) data. The lowest values indicate the most stable genes. The Ct data was recorded by qRT-PCR in a QIAquant 96 5 plex (QIAGEN) following the manufacturer's protocol. Abbreviations: Actin 7 (StACT7), alpha-tubulin (StTUA), elongation factor 1-alpha (StEF1a), COP1-interactive protein 1 (StCIP1), plasma membrane ATPase 4 (StPMA4), BEL1-like homeodomain protein 1 (StBLH1), polyubiquitin 3 (StUBQ3), and plastidic ATP/ADP-transporter (StTLC1). S. thurberi transcripts identified in this study were designated with the prefix "St" and the name of their best homologous match from other plant species. Supplementary Table S28 Expression of cutin biosynthesis-related transcripts during sweet pitaya fruit development normalized with four normalization strategies. Relative expression (RE) was calculated through the 2−ΔΔCt method using elongation factor 1-alpha (StEF1a), alpha-tubulin (StTUA), polyubiquitin 3 (StUBQ3), and StEF1a+StTUA as normalizing genes using the 10 DAF (days after flowering) stage as calibrator. Data represent the mean ± standard error (SE) of each developmental stage (n = 4−6). Different letters denote significant differences (Tukey HSD test, p < 0.05) between developmental stages in DAF. Statistical analysis was carried out through stats packages in R Studio. The Ct data for the analysis was recorded by qRT-PCR in a QIAquant 96 5 plex (QIAGEN) according to the manufacturer's protocol. Abbreviations: Cytochrome p450 family 77 subfamily A (StCYP77A), Gly-Asp-Ser-Leu motif lipase/esterase 1 (StGDSL1), and ATP binding cassette transporter family G member 11 (StABCG11). S. thurberi transcripts identified in this study were designated with the prefix "St" and the name of their best homologous match from other plant species. Supplementary Fig. S1 Sweet pitaya fruit developmental stages. The numbers in the picture indicate the days after flowering (DAF). A longitudinal cut of sweet pitaya fruit at 40 DAF is showed. White bar = 1.0 cm. Supplementary Fig. S2 Homology analysis of assembled transcripts. E value distribution (a, b) and identity distribution (c, d) of the matches in the Swiss-Prot (a, c) and RefSeq (b, d) databases. (a,b) The number inside the pie chart indicates the number of transcripts recorded using that E value. Alignment by BLASTx with an E value threshold of 1 × 10−5. Supplementary Fig. S3 Amplification specificity of the candidate reference genes. Melting curve analysis of the candidate reference genes Actin 7 (StACT7), (a) alpha-tubulin (StTUA), (b) elongation factor 1-alpha (StEF1a), (c) COP1-interactive protein 1 (StCIP1), (d) plasma membrane ATPase 4 (StPMA4), (e) BEL1-like homeodomain protein 1 (StBLH1), (f) polyubiquitin 3 (StUBQ3), (g) and plastidic ATP/ADP-transporter (StTLC1), (h) Transcript quantification and melting curve were recorded in a QIAquant 96 5 plex (QIAGEN) following the manufacturer's protocol. Supplementary Fig. S4 Analysis of the predicted protein StCYP77A from Stenocereus thurberi. (a) Phylogenetic tree of StCYP77A and related proteins of the subfamily CYP77A (CYP77A2, CYP77A4, and CYP77A6) from Solanum lycopersicum (Sl), Solanum melongena (Sm), Nicotiana attenuata (Na), Beta vulgaris (Bv), Carnegiea gigantean (Cg), Arabidopsis thaliana (At), Isatis tinctoria (It), and Hirschfeldia incana (Hi). The database accession number is included next to the protein name. The scale bar of 0.05 represented a sequence divergence of 5%. The number in the branches is the percentage bootstrap value of 1,000 replicates. The highest percentages represent more significant results. The black square shows AtCYP77A4 and AtCYP77A6 from A. thaliana. The black diamond shows the homologous SmCYP77A2 from S. melongena. The red circle and red triangle show StCYP77A from S. thurberi and a protein from the closest related species C. gigantean, respectively. Neighbor-joining (NJ) phylogenetic tree constructed by MEGA11 software. (b) The predicted membranespanning region of StCYP77A. The probability of membrane insertion (Y-axis) and transmembrane region represented by purple color was determined by TMHMM software. (c) Predicted protein domains contained in StCYP77A amino acid sequences determined by InterProScan. Supplementary Fig. S5 Analysis of the predicted protein StGDSL1 from Stenocereus thurberi. (a, b) Signal peptide and topology of StGDSL1 amino acid sequence. (a) The amino acid sequence corresponding to the signal peptide (red, orange, and yellow) and the cleavage site (CS; green dashed line) were determined by Signal P 6.0 software. (b) The signal peptide (orange) and outside (blue) region of the protein sequence were determined by deepTMHMM software. (c) Predicted protein domains contained in StGDSL1 amino acid sequences were determined by InterProScan. Supplementary Fig. S6 Analysis of the predicted protein StABCG11 from Stenocereus thurberi. (a) Phylogenetic tree of StABCG11 and related proteins of the classes ABCG11, ABCG12, and ABCG13 from Arabidopsis thaliana (At), Gossypium arboreum (Ga), Citrus sinensis (Cs), Medicago truncatula (Mt), Solanum lycopersicum (Sl), Eutrema halophilum (Eh), Carnegiea gigantean (Cg), Beta vulgaris (Bv), and Spinacia oleracea (So). The database accession number next to the protein name is shown. The scale bar of 0.10 represented a sequence divergence of 10%. The number in the branches is the percentage bootstrap value of 1,000 replicates. The highest percentages represent higher significant results. The black square beside the protein name shows AtABCG11, AtABCG12, and AtABCG13 from A. thaliana. The red circle and red triangle next to the protein name show StABCG11 from S. thurberi and a protein from the closest related species, C. gigantean, respectively. Neighbor-joining (NJ) phylogenetic tree constructed by MEGA11 software. (b) The predicted transmembrane helices of StABCG11. The probability of membrane insertion (Y-axis) and transmembrane region represented by purple color was determined by TMHMM software. (c) Multiple sequence alignment of StABCG11 and its homologous from A. thaliana (AT1G), S. lycopersicum (Solyc03g), and C. gigantean (KAJ). Amino acids are colored according to the chemistry classification of their side-chain. The darkest blue bars below the protein sequences indicate 100% conservation. Black rectangles show the conserved sequence of the Walker A and B motif and the ABC signature, named below the rectangles. Black width lines below the sequence show the predicted transmembrane helices of StABCG11. Alignment was carried out by MUSCLE in MEGA11 and drawn by ggmsa in R Studio. -
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García-Coronado H, Hernández-Oñate MÁ, Tafolla-Arellano JC, Burgara-Estrella AJ, Tiznado-Hernández ME. . De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes. Vegetable Research 4: e032 doi: 10./vegres-- García-Coronado H, Hernández-Oñate MÁ, Tafolla-Arellano JC, Burgara-Estrella AJ, Tiznado-Hernández ME. . De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes. Vegetable Research 4: e032 doi: 10./vegres--
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ARTICLE Open AccessDe novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes
Vegetable Research 4, Article number: e032 () | Cite this articleAbstract: Stenocereus thurberi is a cactus endemic to the Sonoran desert (Mexico), which produces a fruit named sweet pitaya. One trait that allows the cactus to survive in desert ecosystems is its cuticle, which limits water loss in dry conditions. Nevertheless, the mechanism of cuticle biosynthesis has yet to be described for cactus fruits. Also, transcripts from S. thurberi published in the databases are scarce. This study reports the de novo assembly of the sweet pitaya peel transcriptome. The assembly includes 174,449 transcripts with an N50 value of 2,110 bp. Out of the total transcripts, 43,391 were classified as long non-coding RNA. Functional categorization analysis suggests that mechanisms of response to stress and cuticle biosynthesis are carried out in fruit pitaya peel. The transcripts coding for a cytochrome p450 77A (StCYP77A), Gly-Asp-Ser-Leu motif lipase/esterase 1 (StGDSL1), and ATP binding cassette G 11 (StABCG11), which carried out the synthesis, polymerization, and transport of cuticle components, respectively, were identified. Expression analysis during fruit development suggests an active cuticle biosynthesis at the early stages and the ripe stages, carried out by StCYP77A, StGDSL1, and StABCG11. The dataset generated here will help to improve the elucidation of the molecular mechanism of cuticle biosynthesis in S. thurberi and other cactus fruits.
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- Peel /
- Transcriptome /
- Stenocereus thurberi /
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García-Coronado H, Hernández-Oñate MÁ, Tafolla-Arellano JC, Burgara-Estrella AJ, Tiznado-Hernández ME. . De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes. Vegetable Research 4: e032 doi: 10./vegres-- García-Coronado H, Hernández-Oñate MÁ, Tafolla-Arellano JC, Burgara-Estrella AJ, Tiznado-Hernández ME. . De novo assembly of the sweet pitaya (Stenocereus thurberi) fruit peel transcriptome and identification of cuticle biosynthesis genes. Vegetable Research 4: e032 doi: 10./vegres--Format
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The historical and current research progress on jujube–a superfruit ...
During the past 70 years, jujube research has greatly advanced. A historic leap has been achieved from the initial stage of focusing on summarizing production experiences to a new era of innovative research throughout the whole industry chain covering breeding, cultivation, pest management, fruit storage, transportation, and processing; from morphological research to comprehensive research at the levels of the plant, organ, tissue, cell, molecule, and gene; and from the research of a few individuals to national and international research collaborations.
Genome sequencing and its application
Genome sequencing is the golden key to unlocking the genetic code of life. Genome sequencing-based multiomics analysis combining transcriptome, proteome, metabolome, and phenotypic data has taken horticultural research to a new level.
De novo genome sequencing and pseudochromosome construction
In , de novo genome sequencing of jujube was accomplished (the first in the Rhamnaceae family)12. A strategy combining WGS sequencing, BAC-to-BAC and WGS-PCR-free library was employed to address the impact of the high complexity of the jujube genome, which has a high heterozygosity of 1.90%, a low GC content of 33.41% and a high density of simple-sequence repeats (SSRs) (378.1 per Mb). The assembly (437.6 Mb) covered 98.6% of the estimated jujube genome (444 Mb), and 32,808 protein-coding genes were predicted (http://jujube.genomics.cn/page/species/index.jsp). Later, another jujube genome and the chloroplast genome sequencing of four Ziziphus species were published15,16.
Using an interspecific population between Z. jujuba and Z. acidojujuba, a high-density molecular (SNP) genetic map was constructed by restriction site-associated DNA sequencing17. The joint map across the 12 linkage groups (the same as the basic chromosome number in jujube) spanned .22 cM, with a mean marker distance of 0.32 cM. Combining these genetic linkage groups with the assembled genome sequences, pseudomolecules for each of the 12 chromosomes of jujube were constructed. A total of 23,996 genes (73% of the total annotated genes) were allocated on the 12 pseudochromosomes. Self-alignment of the jujube genome sequences based on the 23,996 gene models identified 943 paralogous gene groups, indicating that the jujube genome may have undergone frequent intrachromosomal fusions and segment duplication during its evolutionary history. A gene block located in the region from 9.20 to 14.68 Mb of pseudochromosome 1 is highly conserved and contains many genes related to sugar metabolism and stress tolerance. An evolutionary divergence analysis of jujube, pear and Prunus mume found that the 4DTv (fourfold synonymous third-codon transversion) rate of jujube peaked at only 0.50, suggesting that no recent whole-genome duplication had occurred in jujube12.
Genome-wide screening of SSR markers and reference genes for RT-qPCR analysis. The density of SSRs in the jujube genome reaches 378 SSRs per Mb, which is approximately two times the density in peach and apple12. Using the genome data, 511 pairs of SSR primers showing high polymorphism were screened and applied for the identification of large-scale hybrid progeny and a genetic diversity analysis18,19,20. A total of 963 jujube germplasms were analyzed by SSRs to construct the core collection and germplasm resource management database21.
Specific reference genes for RT-qPCR of jujube were selected under a variety of conditions and sourced from different tissues/organs, fruit development stages, and biotic/abiotic stresses, providing more choices for further gene expression analysis and functional studies in jujube22,23,24,25,26.
Multiomics-based analysis for the molecular formation mechanisms of some important traits. Combining comparative genome, transcriptome, and metabolome data, the molecular mechanism underlying the high contents of ascorbic acid (AsA) and sugar in jujube fruit (~100 and 2 times those of apple, respectively) were revealed. The l-galactose pathway is the major route for jujube AsA biosynthesis, and the genes encoding the key enzymes involved in the biosynthesis pathway show high-level expression during fruit development12. Meanwhile, the expansion of the MDHAR gene family contributes to AsA regeneration. Further studies indicated that GLDH and MDHAR are the crucial genes in jujube AsA synthesis and recycling, respectively27. The high level of sugar accumulation in jujube fruit is due to the expansion and high-level expression of genes involved in sugar metabolism and transport. In addition, the distinct trait of the ‘bearing shoot falling in winter’ is related to the ethylene and abscisic acid (ABA) pathways12.
The genome sequencing of a drying jujube cultivar ‘Junzao’ and the resequencing of some cultivated and wild jujubes identified the selective sweep regions involved in acid and sugar metabolism and provided insights into an important domestication pattern in fruit taste15. Studies have also proven that sugar transport plays a significant role in sugar accumulation15,28 and jujube fruits have characteristics of nonclimacteric fruits15,29. The ethylene and ABA pathways are involved in regulating jujube fruit ripening30,31.
Some gene families involved in phytoplasma and cold stress and flower and fruit development were identified and analyzed at the genome level22,23,24,32,33,34. A series of gene families and metabolisms responsive to phytoplasma infection were studied, showing that photosynthetic, carbohydrate, and energy metabolism play crucial roles during phytoplasma infection33 and that the MAPK-WRKY pathway is responsive to phytoplasma stress23,24,32.
Germplasm resources and systematic classification
Construction of a highly representative germplasm repository
As one of the longest-cultivated fruit trees in the world, jujube has abundant germplasm resources after undergoing long periods of natural evolution and artificial selection. From the s to s, the first nationwide jujube germplasm investigation was carried out; a total of 700 jujube cultivars and 30 wild sour jujube genotypes were determined through synonym and homonym identification and recorded in the book China Fruit Tree Records-Jujube1.
Based on the nationwide germplasm investigation, the National Chinese Jujube Repository was constructed in Taigu, Shanxi Province, by the Ministry of Agriculture and Rural Affairs of the People’s Republic of China. To date, a total of ~930 jujube genotypes have been preserved, accounting for at least 90% of the total jujube genotypes in the world. Another germplasm repository funded by the State Forestry and Grassland Bureau of China was constructed in Cangxian, Hebei Province, where ~640 germplasm accessions, including some excellent variants of the local leading cultivars, such as ‘Jinsixiaozao’, ‘Wuhezao’, and ‘Dongzao’, are maintained. In addition, Hebei Agricultural University collected and preserved ~200 accessions of sour jujube germplasm and some other species of the Ziziphus genus, such as Z. mauritiana Lam., Z. spina-christi Willd, and Z. nummularia Burm. f.
Evaluation of elite germplasms with unique features
To date, ~700 jujube cultivars and 100 sour jujube genotypes have been evaluated. The evaluations have covered morphological, agronomical, cytological, palynological, nutritional, and reproductive biological traits, as well as biotic resistance and abiotic tolerance2,35,36,37. A number of excellent accessions have been identified, including triploid genotypes such as ‘Zanhuangdazao’38, ‘Pingguozao’39, ‘Jinglinyihaozao’, ‘Shanxitedage’, ‘Hengshuibianzhizao’, ‘Zhenhuluzao’40; the mixoploid genotype ‘Dongzao 2’41; the male-sterile germplasms ‘JMS1’ and ‘JMS2’42; the self-fruitless and self-sterile germplasms ‘Huizao’, ‘Jinsixiaozao 39’, ‘Yuanlingzao’, and ‘Xiangzao’43; the tortuous-branch ‘Dongzao’44; the seedless germplasm ‘Wuhexiaozao’; genotypes that are highly resistant to witches’ broom disease such as ‘Xingguang’45,46; and genotypes that are rich in functional nutrients47,48,49,50,51,52,53,54.
Establishment of the germplasm database and platform
Three representative books on jujube germplasm have been published. The first is China Fruit Tree Records-Jujube, mentioned above. The second is Germplasm Resources of Chinese Jujube10, which recorded accessions of jujube (Z. jujuba Mill.), sour jujube (Z. acidojujuba Liu et Cheng) and Indian jujube (Z. mauritiana L.). The third is The Illustrated Germplasm Resources of Jujube55, in which pictures and research data for 250 cultivars (57 table jujubes, 80 for dehydration, 82 for both dehydration and fresh eating, 17 for processing, and 14 ornamental varieties) were obtained from the National Chinese Jujube Repository (Taigu, Shanxi). In addition, other books such as Descriptors and Data Standards for Jujube Germplasm56, Test Guidelines for Distinctness, Uniformity and Stability—jujube57, Technical Regulators for the Identification of Jujube Cultivars-SSR Marker Method provide references and technical standards for character selection, data collection, testing, and identification in jujube germplasm studies.
The established germplasm platforms include the following:
(1) Internet Information System for Perennial and Asexual Crop Germplasm Resources (http://www.ziyuanpu.net.cn/), which includes the data observed for many years at the National Jujube Repository in Taigu, Shanxi, China;
(2) Chinese Crop Germplasm Resources Information System—jujube (http://www.cgris.net/query/croplist.php), where germplasm checking and analysis can be performed; and
(3) Internet Information System for Jujube Germplasms (http://www.ziziphus.net/zzzy), which provided information observed from local areas about 700 germplasm accessions recorded in China Fruit Tree Records—Jujube.
In addition, the International Cultivar Registration Center for the Ziziphus genus was established in at the Research Center of Chinese Jujube, Hebei Agricultural University under the authorization of the International Society of Horticultural Sciences.
Clarification of the ancestor and the original cultivation center
In the book ‘Qi Min Yao Shu’, published YA, it is clearly recorded that ancient Chinese people used to select the trees with the best tasting fruits of wild sour jujube (Z acidojujuba Cheng et Liu—Z. jujuba Mill. var. spinosa Hu) and cultivate them1,2,3,4. Qu et al. proposed that jujube evolved from wild sour jujube1 based on a systematic study of ancient books, ecological distributions, karyotyping, palynology, and isoenzymes as well as of the transitional types between jujube and sour jujube1. A further cluster analysis of isoenzymes, palynology, and DNA showed that some jujube cultivars and sour jujube genotypes were usually clustered together instead of being totally separated58,59,60, indicating that there are probably several evolutionary pathways from sour jujube to jujube. This result was later confirmed by SSR and cpSSR analysis61,62.
As to the original cultivation center of jujube, outside of China, Iran, and Japan had been regarded as candidates by some scholars outside China. However, the earliest records and evidence from Iran and Japan could only be traced back to YA, when Sino–Japan exchanges became popular and Zhang Qian was sent on a diplomatic mission to west Asia and European countries during the Han Dynasty. According to the author’s investigation in Iran, all the jujube trees that were hundreds of years old were located at key sites on the ancient Silk Road, and Iranian scholars report that the jujube was introduced from China. In the Book of Songs, published YA, it is clearly mentioned that jujubes were already widely cultivated in China. Additionally, according to the unearthed carbonized fruits, jujube was cultivated and utilized in China years ago. It was reported that jujube originated from the Yellow River valley between Shaanxi and Shanxi provinces, China, after studying ancient documents, fossils and modern distributions as well as the transitional genotypes of jujube and sour jujube1,5.
Establishment of the taxonomic system for the Zizhiphus genus, including jujube
Based on the classical taxonomic system, jujube is listed in the Rhamnaceae family, Rhamnales order63. However, the Rhamnaceae family was moved to the Rosales order in the APG III Angiosperm Phylogeny Group Classification based on chloroplast DNA sequencing (Angiosperm Phylogeny Group III, ), which was further confirmed by phylogenic studies on the genome-sequenced plant species using 390 shared genes64.
The classification system for the Ziziphus genus was proposed based on field investigations, textual research on specimens and historical documents65. The genus Ziziphus was grouped into two sections based on geographical distribution, bearing shoot persistence, and leaf hairiness. They are Section Ziziphus Cheng et Liu and Section Perdurans Cheng et Liu. The latter was further divided into Ser. Cymosiflora Cheng et Liu and Ser. Thyrsiflora Cheng et Liu mainly according to the inflorescence type. Most species belong to Sect. Perdurans; only jujube and sour jujube originating from China and Z. lotus L., native to the Mediterranean, belong to Section Ziziphus due to their deciduous bearing shoots.
Regarding the taxonomic relationship between jujube and sour jujube (Z acidojujuba Cheng et Liu—Z. spinosa Hu), four viewpoints have been reported66, i.e., that they are the same species, that jujube is a variety of sour jujube, that sour jujube is a variety of jujube, or that they are two different species. Regarding the obvious differences in distribution, morphology, usage, and historical knowledge of jujube and sour jujube in China, Liu et al. proposed that they could be treated as two different species, Z. jujuba Mill. and Z. acidojujuba Liu et Cheng67,68. However, jujubes and sour jujubes are very closely related, with cross-compatibility and transitional types between them.
The subdivisions of Z. jujuba Mill. and Z. acidojujuba Liu et Cheng were also proposed to consider them as two independent species67. Under Z. jujuba Mill., five forms have been reported, i.e., f. tortuosa Cheng et Liu (Z. jujuba Mill. var. tortuosa Hort., Z. jujuba Mill. cv. Tortuosa), f. lageniformis (Nakai) Kitag. (Z. sativa Gatern. var. lageniformis Nakai, Z. jujuba Mill. var. lageniformis Hort.), f. carnosicalycis (Wang) Cheng et Liu (Z. jujuba Mill. var. carnosicalycis Wang), f. allochroa Cheng et Liu, f. heteroformis Cheng et Liu (Z. jujuba Mill. cv. heteroformis Hort., Z. jujuba Mill. var. quinequeflora Hort.), and f. apyrena Cheng et Liu (Z. jujuba Mill. var. anucleatus Y. G. Chen). Within Z. acidojujuba Liu et Cheng, three forms were confirmed, namely, f. granulata Cheng et Liu, f. trachysperma Cheng et Liu, and f. infecunda Cheng et Liu.
There appear to be at least 2, 16, and 6 scientific names for the jujube genus, the jujube and the sour jujube, respectively, due to different classification viewpoints and poor academic exchange in the past. Based on a systematic study of the historical taxonomic literature, Liu et al. affirmed Ziziphus (rather than Zizyphus), Z. jujuba Mill. and Ziziphus acidojujuba Cheng et Liu as the proper scientific names for the jujube genus, the jujube and the sour jujube, respectively10,65,66,67,68,69.
Breeding and character inheritance
Jujube breeding has a long history. However, until the end of the 20th century, the breeding techniques for Chinese jujube had been mainly focused on selection from seedlings, bud mutants, and local germplasm, even though some new techniques had been incorporated into selection breeding, such as marker-assisted identification and standardized techniques. After entering the 21st century, great progress has been made in polyploidy and cross-breeding in jujube. Genetic engineering has also made some advances, but these applications are not yet fully developed.
Upgrading the breeding objectives
Breeding objectives should take into consideration the characteristics of jujube trees, the demands of all related parties, the breeding trends in fruit trees and breeding practices in jujube70. The overall objective should be to meet the various needs of farmers, processers, marketers and consumers. The specific objectives should include outstanding resistance to biotic and abiotic stresses, dwarfing, low branching ability, thornlessness, early bearing, high and stable yields, high quality, stonelessness, high nutrient levels, various ripening times, ease of transport and storage, and multiple-use cultivars. The major requirements to meet farmers’ needs are reducing inputs, increasing output and accelerating economic returns. Good quality, stonelessness, high nutrient levels, and varied ripening times can satisfy consumers, whose demands have become increasingly critical and diversified. Objectives such as tolerance to transportation and long storage life, varied ripening times, and multiple-use cultivars are marketers’ preferences. A revolutionary novel cultivar could simultaneously satisfy the diverse demands of farmers, processers, marketers, and consumers.
Creating a mixoploid-free polyploid induction system
Given the limitations of traditional selection breeding for obtaining breakthrough cultivars and the extreme difficulty of cross-breeding in jujube, polyploid breeding seems to be a promising prospect. Consumers usually prefer large fruits, but increasing fruit size by applying more fertilizer and plant regulators may result in poor fruit quality. As a result, polyploidy induction has become an ideal breeding approach for obtaining new cultivars with high-quality, large fruits.
Four generations of polyploid induction techniques using colchicine as the main mutagen have been developed for jujube, i.e., in vivo apical bud induction71, in vitro apical or lateral bud induction72, in vitro callus/embryo induction73 and in vivo callus induction74. The fourth-generation technique is to induce polyploidy by treating in vivo calluses induced on branch cuts with colchicine, which could eliminate the severe mixoploidy formation from traditional polyploid breeding and directly produce pure polyploid shoots (Fig. 3). The pure polyploid shoot could form flowers and even set fruits for further evaluation in the same year as the polyploid induction. Consequently, the pure polyploid creation and evaluation period can be shortened by 3–5 years. Until now, a total of 25 triploid, tetraploid, and octoploid strains have been created, among which three excellent tetraploid strains have been released as new cultivars by the Hebei Forestry Cultivar Examination and Approval Committee75,76,77. The novel field technique for homogeneous polyploidy induction has been successfully applied in sour jujube78 and in elm (data not shown).
Auto-tetraploids differ greatly from their diploid counterparts in their morphology, cytology, and nutrient content79. Comparing the tetraploid jujube cultivar ‘Riguang’ and its diploid counterpart ‘Dongzao’, ‘Riguang’ has wider and darker green leaves, higher chlorophyll content, a higher photosynthesis rate, larger stomata, larger pollen and flowers, wider and larger fruits, and an earlier maturation time but is also less vigorous and less cold hardy79. The contents of vitamin C, cAMP, soluble sugars, titratable acids, sucrose, glucose, and fructose were significantly higher in tetraploid ‘Riguang’ fruits than in diploid ‘Dongzao’ fruits79. It was discovered that an autotetraploid sour jujube had higher tolerance to salinity than the diploid, and its preliminary molecular mechanism was illustrated80,81. In addition, triploids of ‘Jinsixiaozao’, ‘Yuanlingzao’, and ‘Changhongzao’ have been created by endosperm culture, but no new cultivar has been released82. Anther/pollen culture has also been practiced in jujube, and some plants have been generated from pollen73,83.
Establishing emasculation-free cross-breeding technology
Cross-breeding, the most powerful breeding method for fruit trees, has not been successfully utilized in jujube. This is a result of several key obstacles, including the extreme difficulty of emasculation of small flowers (~5 mm in diameter), the low fruit-setting rate (only ~1%) and the high embryo abortion rate. The rate of obtaining hybrids in jujube is usually <0.01% by the traditional crossing approach. Since no new gene fusions or multiple trait combinations are available in autopolyploidization and it is difficult to make large breakthroughs via selection breeding, there is no substitute for cross-breeding, and its advantages are also incomparable.
In the last 10 years, a high-efficiency hybrid breeding technology system combining male-sterile germplasm, embryo rescue, net control hybridization, and molecular identification was established. Hybrid plant production was increased by 100 times using the new system, and a large number of hybrid progeny were obtained from 19 cross combinations, of which a number of superior lines were selected70.
Three emasculation-free methods have been developed based on the discovery of two typical male-sterile germplasms and a group of self-fruitless/self-sterile germplasms that can replace male sterility42,43, which effectively overcame the key obstacle to artificial emasculation in jujube. Method 1: Hybrids are produced by using a male-sterile variety as the female parent and a variety with high pollen viability and compatibility as the male parent20,84. Method 2: A self-fruitless or self-sterile variety is chosen as the female parent, and a variety with high pollen viability and compatibility is chosen as the male parent. In the two cases mentioned above, all the offspring from self-fruitless or self-sterile parents can be directly regarded as authentic hybrids. Method 3: is a universal technology free of emasculation, i.e., covering the parents with nets to keep away unexpected pollen donors, pollinating by bees inside the nets, and identifying the hybrids with molecular markers84. This method can produce cross and reciprocal-cross hybrids at the same time85.
The problem of hybrids not being obtained due to heavy early embryo abortion was solved by embryo rescue based on the understanding of the mechanism of embryo abortion and the factors affecting very young embryo culture. These factors included the culture media, inoculation methods, removal or maintenance of the seed coat, combination of growth regulators, and concentrations of lactalbumin hydrolysate, activated carbon, and sucrose86,87,88. The seedling rate of young embryos <30 days after flowering (before the abortion peak) was increased from 3.7 to 40%89. The key techniques included peeling off the seed coat, culturing young embryos together with their endosperm and reverse inoculating young embryos with the chalazal end pointed down on the medium.
In recent years, the interploidy hybridization of jujube and the interspecific hybridization between jujube and sour jujube were successfully carried out20,84,85. With the breakthroughs in cross-breeding technology, the acquisition of a progeny population and the establishment of genetic maps, genetic research into important traits was also carried out.
Several high-density genetic linkage maps have been constructed based on segregation populations of ‘JMS2’ × ‘Xing16’, ‘Dongzao’ × ‘Linyilizao’, ‘Dongzao’ × ‘Jinsi 4’, and ‘Dongzao’ × ‘Yinshanhong’17,90,91,92. The male sterility and kernelless traits are controlled by homozygous recessive genes, and some QTL loci of quantitative traits have also been identified92,93,94,95.
Releasing new cultivars with various maturation times and usages
In the past 30 years, a total of ~200 new cultivars with large fruit, good fruit quality, high resistance to diseases, and varying uses and maturity times were released through polyploid breeding or selection from seedlings, bud mutants, and local germplasms2. Among them, the tetraploids ‘Chenguang’, ‘Hongguang’, ‘Riguang’, and ‘Zhuguang’, bred by Hebei Agricultural University, have been awarded new plant variety rights by the National Forestry and Grassland Bureau of China. The fruits of the tetraploids were 30–50% larger in size, 4–7 days earlier to mature and better tasting than diploid fruits.
A large number of local cultivars, such as ‘Zanhuangdazao’, ‘Linyilizao’, ‘Dongzao’, ‘Qiyuexian’, ‘Junzao’, ‘Huizao’, etc. have been excavated and utilized, which has greatly promoted the rapid development of the jujube industry. Recently, some excellent new cultivars for fresh eating, such as ‘Jinsi 4’, ‘Yueguang’, ‘Zaohongmi’, ‘Zaocumi’, and ‘Zaoqiuhong’, and some for dehydration, such as ‘Yuangling 2’, ‘Shuguang’, ‘Zanshuo’, ‘Yushuai’, and ‘Linhuang 1’, with larger fruit, higher quality and higher resistance to fruit diseases than traditional cultivars, have become the dominant cultivars. These dominant cultivars have replaced the traditional cultivars, which has greatly improved the cultivar structure in China.
Constructing a high-efficiency propagation system
A set of new propagation approaches has been developed on the basis of traditional sucker division. Among them, stimulating sucker propagation by cutting off the roots at the periphery of the vertical projection of the canopy and separating fasciculate suckers can increase the reproductive coefficient, while gathering and nurturing the suckers in a nursery can greatly improve the quality of the root system. Jujube hardwood cuttings are quite difficult to propagate, presenting a rooting rate of usually <30%, and have rarely been used in commercial production. However, green shoot cuttings (semilignified primary extension shoots, secondary shoots, and bearing shoots) root much more easily and have a high reproductive coefficient. The rooting rate can reach as high as 95%96, but its cost and technical requirements are relatively higher than those of other propagation techniques.
Judging from old grafted jujube trees, grafting has been used for at least years. To meet the needs of large-scale development, grafting propagation with sour jujube as the rootstock has been widely used since the late s. In particular, the use of sour jujube seeds, rather than pits, to obtain rootstocks has become the mainstream method; using this method, the seedlings grow faster and more uniformly than in rootstocks obtained from pits2. The use of Paliurus hemsleyanus Rehd. as rootstock can also play a role in the prevention of witches’ broom in jujube in southern China97. Jujube has also been successfully grafted onto Indian jujube (Z. mauritiana Lam.) in subtropical and tropical regions.
The tissue culture of jujube began in . In vitro plantlets were obtained from the stem segments of root suckers in . After , research on jujube tissue culture increased rapidly, and tissue culture with stem tips, stem segments, leaves, anthers, embryos, and cotyledons as explants were all successful83,86,87,99,100. However, propagation via tissue culture has not been used on a large scale in jujube in China because of the high technical requirements, high cost, and late fruiting of micropropagated plants.
Cultivation model and orchard management
Research on jujube cultivation technology has a long history that includes fruitful achievements and has played an important role in promoting the jujube industry. The biological characteristics of jujube are basically understood1. To date, cultivation technology systems have been established for the leading cultivars in their main growing areas with their own characteristics. High-density planting and protected cultivation systems have also been applied commercially after the beginning of the 21st century.
The unique growth and fruiting habits of jujube
Since the s, the biological characteristics of jujube have been studied comprehensively, and a complete theoretical system had been formed by the s1,101. It was revealed that jujube has very strong resistance to abiotic stress, including drought, barren soils, and saline and alkali conditions. It has unique branch and bud characteristics, i.e., usually only the primary shoots can extend, the dormant buds have a very long life, the secondary shoots die back naturally each, the mother-bearing shoots can only extend by ~1 mm per year, and the bearing shoots fall off in the fall. Its flower bud differentiation and fruit set habit are also very distinct, with a short flower bud differentiation time (10 days), a 2-month flowering season, and a low fruit set of only ~1%.
Traditional orchard improvement and high-density orchard construction
Since the s, various cultivation techniques focusing on high yield were developed for the leading cultivars and main production areas, which increased production by over 50%, increased the high-quality fruit rate by over 30%, and reduced pesticide use by over 50%102,103. At the same time, traditional sparse planting systems with large crowns (row spacing and plant height above 5 m) and intercropping jujubes with cereal crops (row spacing ≥12 m) were replaced by dense dwarf planting (2 m × 3 m) and monoculture orchards. After the Asian Olympic Games in Beijing in , dense cultivation was developed for dwarf fresh jujube, and even superdense plantings (grass orchards) with densities of up to 15,000 plants per hectare were established. After entering the 21st century, in the desert of southern Xinjiang Province, China, a novel cultivation model for high early yields and high fruit quality was established. This method is characterized by the direct sowing of the rootstock seeds (sour jujube) in orchards followed by the in situ grafting of the target cultivar. Starting with a superhigh density (0.5 m × 1.0 m), the density is gradually decreased to 1.0–1.5 m × 4.0 m. This new model obtains good yields (5–8 t/ha) in the year of grafting (Fig. 4) and maintains the high yield at over 15 t/ha 3–5 years later, which is 3–5 years earlier than this yield could be achieved in a traditional orchard104.
Protected cultivation systems for fresh jujube production
After entering the 21st century, protected cultivation techniques for fresh jujube have developed gradually. Plastic house and Chinese solar greenhouse cultivation (a plastic house with thick back wall as a thermal mass) have been successful in North China and have formed large-scale production regions of over 10,000 ha in Dali County in Shaanxi Province and Linyi County in Shanxi Province in China. In this case, the maturity period can be advanced by 1–4 months105,106. These techniques effectively solve the problem of a short supply period for open field cultivation and can increases revenues by 3–5 times. Solar greenhouses along hillsides facing the sun in the Taihang Mountains of Hebei Province have the advantages of lower investment costs, better sunlight, and much better heat retaining properties than a traditional greenhouse by using the mountain as the back wall of the greenhouses107. The cultivation of fresh jujubes in plastic shelters has resulted in great success in rainy southern China108; this method can greatly reduce the fruit cracking caused by rain at the maturity stage from 70 to <10%.
For fresh eating jujubes, it was found that promoting the lignification of bearing shoots through extremely heavy pruning may accelerate fruiting, increase yield and result in larger fruit109. This technique has become a common practice in fresh jujube production. On the other hand, the lignification of bearing shoots changes the deciduous habit of bearing shoots and increases the pruning labor costs.
Pest and disease management
According to a comprehensive investigation, more than 100 pests and diseases have been observed in jujube1. Only approximately ten of them cause severe yield and quality losses, such as peach fruit moth, jujube inchworm, Ancylis sativa Liu, Tetranychus viennensis Zacher, jujube rust, jujube witches’ broom, and fruit cracking. After the beginning of the 21st century, outbreaks of pests and diseases, including Lygocoris lucorum, Euzophera batangensis, Ceratitis capitata, jujube flies, fruit cracking, and fruit shrinking, have become increasingly severe102,110,111,112,113,114.
High-efficiency management systems for the main diseases and pests in jujube mentioned above have been established in China3,46,103. However, high-efficiency, low-cost practical management systems for fruit cracking and fruit shrinking disease have not been developed; these conditions have a great influence on jujube yield and quality. In addition, due to the economic decline of the comparative benefits of jujube, jujube witches’ broom is becoming serious again in orchards due to poor management.
Postharvest physiology and fresh storage
Revealing the postharvest physiological characteristics of jujube fruit
Jujube is difficult to keep fresh. Under normal room temperature and humidity conditions, fresh jujube loses moisture quickly and loses crispness within 3–5 days. It ferments readily and lose firmness when it is tightly sealed in conventional plastic bags under cold storage. A postharvest physiological study revealed the main factors influencing fruit preservation in jujube115. At present, there are two opposing viewpoints about the respiratory type of jujube fruit, i.e., climacteric or nonclimacteric, even for the same cultivar (‘Dongzao’)116,117,118.
Preservation technology systems for fresh jujube
Many reports on fresh fruit preservation techniques in jujube have been published. The practical techniques include cold storage, controlled atmosphere storage, decompression storage, and controlled freezing-point storage119,120,121,122. Qu et al. reported that ‘Shanxixiaozao’ could be stored for 70 days at 0 ± 1 °C and 60% RH119. Chen et al. indicated that jujube was sensitive to CO2 and that fruit browning occurred quickly under the conditions of 10% CO. Zhang et al. found that the respiration rate, ethylene release, and cell membrane permeability of ‘Dongzao’ stored at 0 ± 0.5 °C were significantly inhibited compared with those of jujube stored at room temperature121.
Hypobaric storage can delay ripening and aging and inhibit the fermentation of jujube fruit by providing low-temperature, low-oxygen storage conditions123. Wang et al. proved that the best storage conditions for fresh jujube were at a temperature of −1 to −2 °C, relative humidity of 95%, 2% O2 and 0% CO. Chen et al. showed that the percentage of healthy fruit and the edible rate of ‘Dongzao’ jujube stored at −2 °C for 100 days were 7.4% and 20.2% higher than those of jujube stored at 0 °C125. Fu found that controlled freezing-point storage was better than normal cold storage in terms of delaying ripening and aging126. Currently, under the optimal storage conditions, half-red fresh jujube can be preserved for 2–3 months or even more than 4 months.
However, in addition to the storage conditions, the duration of fresh jujube storage and the percentage of fruit losses are also influenced by the preharvest cultivation technology and directly by the pathogen load on the fruit in the orchard14,100,113,127,128.
Postharvest treatments
In the past 20 years, postharvest treatment technology for Chinese jujube has made great progress. Fruit drying technology has gradually changed from traditional natural drying under the sun to dehydration in a drying room or by drying machine129. It takes ~1 month for natural drying or air drying to be complete, while the time required can be reduced to 1 day or even less with artificial drying. Compared with those under natural drying, the preservation rates for vitamin C, total sugar, sucrose, fructose, glucose, soluble protein, and other nutrients under artificial drying are significantly improved130,131,132.
In recent years, equipment for jujube fruit sorting or integrated cleaning and sorting has been developed and widely applied in the jujube industry in China133,134,135. The combination of artificial drying, mechanical cleaning, and automatic sorting can significantly improve the appearance of commercial fruit, increase production efficiency and economic benefits, and reduce losses after harvest.
Nutritional analysis and processing
Dominant nutrients and their spatiotemporal distribution
To perform nutritional analysis and intensive processing on jujube, efficient extraction and determination methods were established and optimized for 23 kinds of nutrient components (7 vitamins, 3 triterpenic acids, 8 amino acids, aromatics, cAMP, polysaccharides, flavonoids, and pigments) in jujube54,136,137,138,139,140,141,142. Converting dehydroascorbic acid to AsA (vitamin C) resolved the bottleneck problem in the determination of dehydroascorbic acid, and accurate determination methods for the two kinds of vitamin C in jujube were finalized141,143. The nutrient components in different organs, different fruit developmental stages, and different varieties were systematically analyzed53,54,144,145,146,147. Jujube leaves are rich in leucine, vitamin B6, carotene, betulinic acid, and ursolic acid, the flowers are rich in vitamin B1 and leucine, and mature fruits are rich in cAMP, functional sugars, vitamin B, triterpenic acid, proline, and some other important functional components in addition to the well-known carbohydrates and vitamin C.
Jujube is an important traditional herb and tonic. Comprehensive studies have shown that the most advantageous nutritional features of jujube fruit include its contents of soluble sugars (2–3 times the levels in other fruits), vitamin C (100 times the level in other fruits), cAMP ( times the level in other fruits), vitamin B, triterpenoid acid, proline, polysaccharide, flavonoids, iron, potassium, calcium, and zinc. Therefore, jujube has broad prospects as a material for the development of healthy foods with high nutrition value.
Varied processing techniques
There are many traditional processed jujube products, such as candied jujube, smoked jujube, stoneless sugared jujube, jujube liquor, liquor-saturated jujube, jujube jam, jujube paste, and so on103,148,149. In the last 30 years, various new products, such as jujube juice, jujube powder, jujube slices, jujube tea, jujube beer, jujube essence, and jujube pigment, have been developed149.
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