Research Papers

• Genome-wide Identification and Analysis of Apple WUSCHEL-related homeobox（WOX）Family Genes
• WANG Chukun1，HAN Pengliang1，WANG Yongmei2，WANG Pengfei2,*，and HU Dagang1,*
• Acta Horticulturae Sinica. 2019, 46(6): 1021-1032. DOI:10.16420/j.issn.0513-353x.2018-0716
• Abstract ( 476 ) HTML ( 1118 ) PDF (2646KB) ( 1118 ) 　　　
• In our study，we identified 12 WOX family genes, by bioinformatics methods and the apple genome databases，and further analysis was also produced. Phylogenetic analysis showed that the WOX family in Malus × domestica and Arabidopsis can be divided into three clades，including modern clade，intermediate clade and ancient clade. All the members of the WOX family in Malus contained a common motif，motif-1，and different branch-specific motifs existed in different branch members. The analysis on gene structures suggested that WOX family members contained 2 to 4 exons. The chromosome location showed that 11 family members were located on 7 chromosomes of apple，and one is located on chr00 respectively. The analysis of gene expression patterns showed that all members were constitutively expressed in different tissues and organs and preferentially expressed in fruit. The codon bias analysis showed that the apple WOX family genes are less preferred.
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• Cloning and Functional Characterization of an Ethylene Response Factor MdERF1B-like in Apple
• ZHANG Jing1，CI Zhijuan2，XU Haifeng1，JIANG Shenghui1，FANG Hongcheng1，WANG Yicheng1，ZHANG Zongying1，YANG Guanxian1，and CHEN Xuesen1,*
• Acta Horticulturae Sinica. 2019, 46(6): 1033-1044. DOI:10.16420/j.issn.0513-353x.2018-0739
• Abstract ( 301 ) HTML ( 801 ) PDF (2450KB) ( 801 ) 　　　
• The expression levels of genes involved in anthocyanin and ethylene biosythesis were analyzed via qRT-PCR using uncolored and colored fruits of‘Taishan Zaoxia’apple at different developmental stages. An ethylene response factor was isolated and tentatively named as MdERF1B-like （MDP0000167207），with an open reading frame of 690 bp encoding a protein of 229 amino acid residues. The expression level of MdERF1B-like was consistent with the expression trends of anthocyanin synthesis related genes MdDFR，MdANS and the regulatory gene MdMYB9 in the colored and uncolored‘Taishan Zaoxia’fruit. Phylogenic analysis indicated that MdERF1B-like was located in group IX and was closely related to PyERF1B-like. Overexpression of MdERF1B-like in‘Orin’calli led to the significantly higher anthocyanin accumulation than in the control. The MdMYB9 promoter sequence of 746 bp was analyzed，which contained an ERF binding RAA motif in its promoter，and yeast one-hybrid assay showed that MdERF1B-like bound with MdMYB9 promoter. Furthermore，luciferase reporter assay was used to verify that MdERF1B-like can promote the transcriptional activity of MdMYB9 promoter. Therefore，MdERF1B-like may promote the accumulation of anthocyanin through regulating the expression of MdMYB9.
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• Genetic Diversity of the Apricot Germplasms from North & Northeast China
• LIU Shuo1,2，LIU Ning1，ZHANG Qiuping1，ZHANG Yuping1，ZHANG Yujun1，XU Ming1，MA Xiaoxue1，and LIU Weisheng1,*
• Acta Horticulturae Sinica. 2019, 46(6): 1045-1056. DOI:10.16420/j.issn.0513-353x.2018-0477
• Abstract ( 309 ) HTML ( 670 ) PDF (1462KB) ( 670 ) 　　　
• In this study，we revealed the genetic diversity and structuration of 51 apricot accessions from North and Northeast China. Bayesian clustering of these apricot accessions was addressed using 55 microsatellites that were widely distributed across the Texas × Earlygold linkage map. The most relevant levels of different genetic basis（the number of groups）were detected at K = 5，representing the highestvalue of ΔK. Thus，we proposed there were a total of five genetic basis of cultivated apricots from both North and Northeast China. The most representatives of the Northeast Chinese apricot were found in the clustering group Ⅱ and Ⅴ. Genetic diversity was estimated on these five clustering groups in term of Shannon’s index（I），which was 1.305 on average，and ranged from 1.181 in group Ⅴ to 1.568 in group Ⅳ. The Nei’s genetic distance matrix showed the highest pairwise value of 0.398 between group Ⅴ and mixture group，and the lowest pairwise value of 0.156 between group Ⅲ and group Ⅳ. The averaged pairwise Nei’s genetic distance was 0.262. Furthermore，principal coordinate analysis also showed a clear difference between group Ⅱ and Ⅴ，even there was little genetic variant among North and Northeast apricots. We selected forty-one available microsatellites and obtained a total of 140 rare alleles，with an average of 2.74 for each. The highest number of rare alleles was found in‘Limixing’accession，represented 10% total variation. However，there was no rare alleles detected in a few apricot accessions，e.g.‘Dunhulu’，‘Xinshiji’and‘Guanyinlian’
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• Effect of Storage Temperature on the Peel Surface Structure and Wax Content of‘Shatangju’Mandarin（Citrus reticulata）Fruit
• XU Chengxiang*，WU Xiulan，MA Yanping，ZHENG Fuqing，YE Simin，and CHEN Xiaoting
• Acta Horticulturae Sinica. 2019, 46(6): 1057-1067. DOI:10.16420/j.issn.0513-353x.2018-0656
• Abstract ( 271 ) HTML ( 785 ) PDF (702KB) ( 785 ) 　　　
• To reveal the relationship between cold storage effect of citrus fruit and peel surface structure，wax content and chemical composition，this study took the mature fruits of‘Shatangju’mandarin（Citrus reticulata）as study materials，collected into plastic film microporous fresh-keeping bags，and stored under （14.2 ± 2.8）℃ natural room temperature（the control）and（6.5 ± 0.5）℃ refrigerated warehouse temperature （cold storage）for 90 d，respectively. During storage，peel surface structure，wax content and composition，flavor quality，water loss and decay indexes of the fruits were analyzed periodically. The results showed that the peel wax of‘Shatangju’mandarin fruits stored under room temperature was degraded rapidly，and peel surface structure changed significantly，whereas the peel wax and surface structure of fruits stored under cold temperature was well protected. Cold storage significantly inhibited the reduction of peel wax of‘Shatangju’mandarin，especially the reduction of long-chain aliphatic alcohol，branched paraffin，olefin，and olefin aldehyde；the soluble sugar and organic acid contents and sugar-acid ratio were kept relatively stable. Cold storage reduced the odorous substances ethanol and acetaldehyde contents of‘Shatangju’mandarin，inhibited membrane lipid peroxidation and increase of cell membrane permeability，and effectively reduced the fruit weight loss and decay.
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• Characterization of 4-coumarate：CoA Ligase（4CL）Gene Family in Citrus
• SHEN Wanxia，WANG Zhibin，XUE Yang，ZHAO Wantong，ZHU Shiping，and ZHAO Xiaochun*
• Acta Horticulturae Sinica. 2019, 46(6): 1068-1078. DOI:10.16420/j.issn.0513-353x.2018-0993
• Abstract ( 502 ) HTML ( 777 ) PDF (1665KB) ( 777 ) 　　　
• 4-coumarate co-enzyme A ligase（4CL） gene is a gene family in the plants. It is responsible for biosynthesis of flavonoides and lignin. A group of 4CL-like genes have been discovered from the genomic database of Citrus clementina. Analysis of their protein structures indicated that only three genes possessed typical characters of 4CL family. Phylogenetic relationship analysis divided those three citrus Cit4CL genes into two groups：ClassⅠand ClassⅡ. Gene expression profiles in Meyer lemon[C. limon（L.）Burm. f.] demonstrated a tissue-specific and temporal-specific fashion. The expression of Cit4CL1 was highly positively correlated with the concentration of flavonoids，indicating that this gene is important in the biosynthesis of flavonoids. However，the expression of the Cit4CL2 and Cit4CL3 genes did not relate to the flavonoids contents，but showed strong relationship with the tissues where the lignin biosynthesis occur red. This suggested that those two genes could be involved in the lignification. This study provided the basic information on function of 4CL family genes in citrus.
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• Comparative Heterosis Analysis of Cabbage Based on Transcriptome Data of Cabbage Heads Leaves
• LI Shengjuan，XU Zhongmin*，GUO Jia，ZHANG Enhui，JIANG Jiao，and SHI Wenwen
• Acta Horticulturae Sinica. 2019, 46(6): 1079-1092. DOI:10.16420/j.issn.0513-353x.2018-1040
• Abstract ( 281 ) HTML ( 577 ) PDF (1272KB) ( 577 ) 　　　
• In two F1 hybrids，we performed heterosis analysis through field traits survey and transcriptome sequencing of cabbage heads leaves. The result found that among the nine horticultural traits，head weight and main petiole weight showed significant differences between F1 hybrids and their parents，among which the head weight exhibited a high value of MPH（mid-parent heterosis）and HPH（high-parent heterosis）in the two F1 hybrids，which means the yield heterosis is obvious. Four groups of differentially expressed genes（DEGs）were compared through transcriptome analysis of cabbage heads leaves. We found that the number of DEGs between F1 hybrids and paternal lines were significantly higher than that between F1 hybrids and their maternal lines in the same criteria. It means similar gene expression profile between maternal lines and their F1 hybrids or a bigger contribution of maternal lines than paternal lines in the formation process of cabbage heads leaves of F1 hybrids. Besides，the fold change of up-regulated genes were higher than that of down-regulated genes，which implied an important role of up-regulated genes in the formation process of cabbage heads leaves of F1 hybrids. The DEGs were further conducted GO（Gene Ontology），COG（Cluster of Orthologous Groups of proteins），KEGG（Kyoto Encyclopedia of Genes and Genomes）pathway enrichment and alternative splicing analysis. The result found that DEGs are highly involved in growth and development，carbohydrate transport and metabolism，signal transduction and amino acid biosynthesis，transport and metabolism pathways. Seven DEGs were randomly selected to perform qRT-PCR and the result was basically consistent with RNA-seq，demonstrating the reliability of transcriptome data. The DEGs that we screened associated with the formation process of heterosis of cabbage heads leaves，able to provide data support for the subsequent research on the molecular mechanism of cabbage heterosis.
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• Genome-wide Identification and Expression Analysis of the SAUR Gene Family in Cucumis sativus
• WANG Hongfei and SHANG Qingmao*
• Acta Horticulturae Sinica. 2019, 46(6): 1093-1111. DOI:10.16420/j.issn.0513-353x.2018-0873
• Abstract ( 349 ) HTML ( 874 ) PDF (4185KB) ( 874 ) 　　　
• SAURs（Small auxin-up RNAs）are the early auxin-responsive genes，which play critical roles in regulating plant growth and development. In the present study，we identified the members of SAUR gene family in cucumber（Cucumis sativus）and analyzed their evolution，gene structure，tissue-specific transcription patterns，and responses to light intensity，temperature，and water potential. A total of 73 CasSAUR genes were identified and they were distributed onto the 7 chromosomes with 60% genes appearing in 2 clusters. The phylogenetic tree indicated that CsaSAURs could be further divided into 8 subfamilies and each of subfamily included a range of genes. The cis-acting elements，responding to IAA，ABA，GA，JA，SA，drought，low temperature，and mechanical damage，were identified by analyzing the promoter sequence of CsaSAURs. The members of CsaSAUR gene family exhibited different expression patterns and some of them can be activated or repressed by low light，high temperature，and high water potential. Among the 18 CsaSAURs highly expressed in hypocotyl，only CsaSAUR15 is up-regulated by the three environmental factors：low light，high temperature and high water potential.
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• Sterility Characteristics and the Genetic Law of a Reverse Thermo- sensitive Genic Male Sterile Mutant E6421S in Peppers
• FENG Wenpeng1，ZHOU Shudong2，YANG Bozhi2，YI Ting2，XIE Lingling2，Liu Feng2,*，and MA Yanqing1,*
• Acta Horticulturae Sinica. 2019, 46(6): 1112-1121. DOI:10.16420/j.issn.0513-353x.2018-0900
• Abstract ( 200 ) HTML ( 535 ) PDF (2742KB) ( 535 ) 　　　
• The critical fertility transition temperature, physiological and biochemical characteristics and genetic law of a reverse thermo-sensitive male sterile mutant E6421S in peppers were studied. The results showed that the critical fertility transition temperature of E6421S was 28 ℃. It was fertile above 28 ℃，and was sterile below 28 ℃. Microscopic observation in 25 ℃ showed that the tapetum of E6421S adhered to pollen mother cells at tetrad stage，leading to the abortion of pollen mother cells. Physiological and biochemical analysis showed that the soluble protein content and catalase activity of E6421S flower buds were significantly lower than those of the original breed with normal fertility，while the free proline content decreased with the development of flower buds, which was opposite to that of the original breed with normal fertility. The investigation of population traits of E6421S and the normal fertile original variety 6421 hybrid progenies showed that the sterility trait of E6421S was single-gene controlled recessive trait.
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• Expression and Function Analysis of AGL6 Homologous Genes in Cymbidium ensifolium
• WU Jinghua，YANG Chao，and WU Shaohua*
• Acta Horticulturae Sinica. 2019, 46(6): 1123-1133. DOI:10.16420/j.issn.0513-353x.2018-0760
• Abstract ( 276 ) HTML ( 707 ) PDF (6132KB) ( 707 ) 　　　
• CeAGL6，a gene belongs to AGL6 class of the MADS-box gene family，was isolated from a normalized full-length cDNA library of Cymbidium ensifolium based on pooling strategy combined with PCR-based screening method. After bioinformatics analysis of CeAGL6，expression patterns，interacting protein and tobacco genetic transformation were performed to identify its functions in the flower development of Cymbidium ensifolium. Sequence analysis revealed the highly conserved MADS domain，K domain, and a typical motif of AGL6 class of MADS-box gene family in CeAGL6. The highest expression level of CeAGL6 was found in sepal，followed by pedicels，low level in petal，lip，and column，and expression in leaf and root was not detected. Overexpression of CeAGL6 caused an advanced flowering and novel phenotypes of four-petal flower，six-petal flower，petaloid stamens and a variety of irregular five-petal flower in transgenic tobacco. Yeast two-hybrid analysis indicated there were interactions between CeAGL6 and CeAP1，CePI1，CeAG1 or CeSEP3，but the homodimers cannot form by itself. The results showed that CeAGL6 was involved in promoting flowering and flower organ development of Cymbidium ensifolium.
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• Effect of OfSVP on Flower Bud Differentiation in Response to Ambient Temperature in Osmanthus fragrans
• ZHU Yimin，WANG Qianqian，DONG Bin，ZHANG Chao，and ZHAO Hongbo*
• Acta Horticulturae Sinica. 2019, 46(6): 1134-1144. DOI:10.16420/j.issn.0513-353x.2018-0972
• Abstract ( 264 ) HTML ( 553 ) PDF (7078KB) ( 553 ) 　　　
• SVP（SHORT VEGETATIVE PHASE）is a kind of MADS-box transcription factor that regulates plant flowering in response to temperature. It plays an important role in flower bud differentiation. In order to explore the effect of SVP gene in Osmanthus fragrans on flower bud differentiation under different temperature treatments，we observed the anatomical structure of the flower bud differentiation process of Osmanthus fragrans‘Yabhong’under different temperatures （19 ℃ and 25 ℃）. The results showed that compared with 25 ℃，the low temperature of 19 ℃ can significantly promote the flower bud differentiation process of Osmanthus fragrans‘Yabhong’，the most significant effects were inflorescence differentiation and pistil differentiation. qRT-PCR analysis showed that the seven OfSVP genes were expressed in different developmental stages of Osmanthus fragrans‘Yabhong’，and the expression of OfSVP4，OfSVP6，OfSVP7 began to decrease from the inflorescence differentiation stage and reached the lowest level in the pistil differentiation stage.，but the expression level of treatment at 19 ℃ was always lower than 25 ℃ treatment. The expression levels of downstream genes FT，SOC1 and GA20ox2 treated at 19 ℃ were basically higher than 25 ℃ treatment，negatively correlated with OfSVP4，OfSVP6，OfSVP7. Therefore，OfSVP4，OfSVP6，OfSVP7 may be a key gene in response to low temperature-induced flower bud differentiation in Osmanthus fragrans，which may affect the process of flower bud differentiation by regulating the expression of FT，SOC1 and GA20ox2.
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• Flavonoid Components and Their Effects on Flower Colors in Camellia nitidissima，White C. japonica and Their Three Hybrid Cultivars
• LI Xinlei1,*，WANG Jiatong1,2，SUN Zhenyuan2，WANG Jie1，YIN Hengfu1，FAN Zhengqi1，and LI Jiyuan1
• Acta Horticulturae Sinica. 2019, 46(6): 1145-1154. DOI:10.16420/j.issn.0513-353x.2018-0603
• Abstract ( 646 ) HTML ( 684 ) PDF (1441KB) ( 684 ) 　　　
• The flower colors，flavonoid components and contents in dark yellow Camellia nitidissima，white C. japonica and their pale yellow hybrid cultivars were studied. The flower colors were measured by CIE L*a*b* scale，and flavonoids were qualitatively and quantitatively analyzed by ultra-performance liquid chromatography quadrupole-time-of-flight mass spectrometry. The relationship between flower colors and flavonoid components was explored by analyzed by multiple liner regression analyses. Ten flavonoids were detected in C. nitidissima，white C. japonica and their three hybrid cultivars. The flavonoids including pelargonium-3-O-glucoside（Pg3G），luteolin-7-O-rutinoside（Lu7R），eriodictyol（Er）and genistin（Gin）were identified in C. nitidissima for the first time. Pg3G，Er and Gin were not determined in white C. japonica‘Yinbai Chalis’and‘Baifeng’，and the contents of Lu7R were extremely low. The main components of C. nitidissima were quercetin-3-O-glucoside（Qu3G），quercetin-3-O-rutinoside（Qu3R），quercetin-7-O-glucoside（Qu7G），kaempferol-3-O-glucoside（Km3G），Pg3G and Lu7R. The contents of luteolin（Lu），kaempferol（Km）and Er in hybrid cultivars surpassed their parents，and those of the rest and total flavonoids were between their parents. Qu3G and Qu3R were the important components which decided the yellow color of C. nitidissima and its hybrid cultivars，and the increase of their contents caused the flower color to remarkably turn yellow. The accumulation of Qu3G significantly enhanced the brilliance of flower color，and Pg3G affected the color tone.
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Research Notes

• Molecular Identification and Genetic Diversity of“Candidatus Liberibacter asiaticus”in W. Murcott Tangerine
• CHEN Yanling，ZHENG Zheng，XU Meirong，and DENG Xiaoling*
• Acta Horticulturae Sinica. 2019, 46(6): 1155-1162. DOI:10.16420/j.issn.0513-353x.2018-0714
• Abstract ( 277 ) HTML ( 517 ) PDF (1378KB) ( 517 ) 　　　

• In December 2017，the W. Murcott tangerine trees，which were newly introduced in Honghe，Yunnan，showed typical HLB symptoms，i.e. blotchy mottle and“red nose”. Leaves and fruit samples of W. Murcott were collected for DNA extraction from midrib and tangerine pith for PCR detection，and sequencing by targeting the 16S rRNA gene and β-operator gene of “Candidatus Liberibacter spp.”. The results showed that samples collected from W. Murcott could be amplified the specific bands of “Candidatus Liberibacter asiaticus”（CLas）. The phylogenetic analysis based on the 16S rRNA gene and β-operator gene revealed the citrus Huanglongbing pathogen of W. Murcott belonged to CLas. In order to further analyze the genetic diversity of CLas，specific primers of three types of prophage were used to amplify DNA samples collected from W. Murcott. The result indicated the high genetic diversity of CLas samples from W. Murcott in Yunnan.

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• Cloning of Potato StRcd1 and Its Expression Analysis Under Abiotic Stress
• CHEN Yingping1，WANG Fang1,2,*，WANG Jian1,2，SUN Haihong1,2，and HE Miaomiao1,2
• Acta Horticulturae Sinica. 2019, 46(6): 1163-1171. DOI:10.16420/j.issn.0513-353x.2018-0998
• Abstract ( 336 ) HTML ( 602 ) PDF (1185KB) ( 602 ) 　　　

• The Rcd1 protein is the major subunit of the CCR4-NOT protein complex and is one of the most conserved proteins found in eukaryotes，and its homologs are expressed in a variety of differentiated tissues. In order to understand the function of Rcd1 protein in response to abiotic stress in potato，the StRcd1 gene was cloned from potato cultivar‘Qingshu 9’. The expression pattern of the gene under simulated drought stress and salt stress was analyzed. The results showed that the full length of StRcd1 was 1 223 bp，the open reading frame was 897 bp，encoding 298 amino acids，and the subcellular cells were located in the nucleus. StRcd1 was highly expressed in potato tubers and responded to drought and salt stress，but the expression patterns in different tissues were different. The expression of the roots was the highest under the salt stress of 12 h and drought stress of 24 h，which were 5.96 times and 9.37 times of the control，respectively. It is speculated that StRcd1 plays an important role in response to drought and salt stress in potato.

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• Chromosome Karyotype Analysis and Development of SSR Molecular Markers in Toona sinensis
• YU Pengfei1,2，SUN Xiaojian2，LI Chenchen2，ZHANG Xu2，ZHENG Wei2，and LIU Changjin1,2,*
• Acta Horticulturae Sinica. 2019, 46(6): 1172-1182. DOI:10.16420/j.issn.0513-353x.2018-0903
• Abstract ( 258 ) HTML ( 583 ) PDF (2558KB) ( 583 ) 　　　
• Chromosome karyotype analysis and SSR molecular marker development of Toona sinensis were conducted. The karyotype analysis result showed that the number of chromosomes in both populations was 2n = 56，and all of karyotypes for the populations was 2A type，the chromosome of T. sinensis was relatively primitive with little variation. 66 921 Unigenes were obtained by transcriptome sequencing analysis from T. sinensis. A total of 13 324 SSRs were identified from 11 184 Unigenes. The frequency of SSRs from these Unigenes was 19.91%，and the mean distribution distance of loci was 3.84 kb. Meanwhile，the major types such as mononucleotide，dinucleotide and trinucleotide accounted for 62.33%，19.66% and 15.99%，respectively. Furthermore，A/T was the predominant mononucleotide repeat type（62.23%），AG/CT was the predominant dinucleotide repeat type（10.31%），and AAG/CTT was the predominant trinucleotide repeat type（4.85%）. 8 218 pairs of SSR primers were found by Primer 3.0. Randomly 19 pairs of primers were selected for PCR amplification by 17 T. sinensis samples，and 6 PCR products showed clear and reproducible results indicating the polymorphism among these samples.
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• Effects of Soil Boron Applications on Photosynthetic Pigments and Physiologic-biochemical Indexes of Chrysanthemum
• LIU Panpan，XIAO Zidie，HUANG Kaiwei，WANG Pengfei，LI Tianpeng，and YANG Lanfang*
• Acta Horticulturae Sinica. 2019, 46(6): 1183-1191. DOI:10.16420/j.issn.0513-353x.2018-0937
• Abstract ( 216 ) HTML ( 596 ) PDF (1622KB) ( 596 ) 　　　
• A pot experiment of cultivating chrysanthemum with soil boron applications at 0，0.2，0.5，1.0，2.5，5.0 and 10.0 mg ? kg-1 was conducted to understand the effects of boron on the physiology and biochemistry of chrysanthemum，in which the content of photosynthetic pigments，soluble sugar，vitamin C，proline（Pro），malondialdehyde（MDA）and the activity of catalase（CAT）were measured during the growth of chrysanthemum. The results showed that the suitable soil boron applications improved the flowering and increased the height of chrysanthemum，but the excessive applications delayed the flowering. The rate of 2.5 mg ? kg-1 increased the content of chlorophyll，helped maintain the stable value of chlorophyll a to chlorophyll b and the content of carotenoid in chrysanthemum leaves. Soil boron application rates of 0.2–10.0 mg ? kg-1 increased the content of soluble sugar during the fast growing period，and the application of rates between 0.2 to 5.0 mg ? kg-1 decreased and that of 10.0 mg ? kg-1 increased the content of soluble sugar during the flowering period. The applications of 0.2 and 0.5 mg ? kg-1 increased and 5.0 and 10.0 mg ? kg-1 decreased the CAT activity in chrysanthemum leaves during the fast growing period，but all applications increased the CAT activity during flowering period. The vitamin C content in chrysanthemum leaves increased by boron applications of 0.5 to 2.5 mg ? kg-1，but decreased by applications of 5.0 and 10.0 mg ? kg-1. The content of Pro in chrysanthemum leaves decreased 7.9%–75.5% as the rate of soil boron applications varied. The boron applications of 0.2 to 2.5 mg ? kg-1 had no significant effect on the content of MDA，but the applications of 5.0 and 10.0 mg ? kg-1 increased the content of MDA significantly. In conclusion，the suitable soil boron application rate for the growth of chrysanthemum under this experiment was under 2.5 mg ? kg-1.
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• Analysis of Different Expressed Genes of Rhododendrons Under Salinity Stress by cDNA-SCoT
• ZHENG Fuchao1，GENG Xingmin1,*，YUE Yuanzheng1，SU Jiale2，and JIA Xinping2
• Acta Horticulturae Sinica. 2019, 46(6): 1192-1200. DOI:10.16420/j.issn.0513-353x.2018-0648
• Abstract ( 172 ) HTML ( 536 ) PDF (2172KB) ( 536 ) 　　　
• Soil salinization is one of the main factors that limit the distribution and landscape application of Rhododendron. To explore the molecular mechanism of Rhododendron resistance to salt stress，R.‘Jiangnan Chunzao’and R. obtusu‘Yanzhi Mi’seedlings were used as the materials to analyse different expressed genes under salt stress by the method of cDNA-SCoT. The results showed that 40 primers could amplify more than 90 bands，most of which were between 100-1800 bp in length. Thirty two bands with obvious differences were selected for recovery. Fifteen high-quality EST sequences were obtained by sequencing after the transformation. Bioinformatics analysis showed that the differential genes in Rhododendron seedlings exposed to salt stress mainly coded catalase，LRR receptor-like serine / threonine protein kinase At1g63430 Structure X1，Shc-related protein，photosystem Ⅱ protein D1，PTS fructose transporter subunit ⅡABC etc，and involved in cell structure，defense response，metabolism，energy metabolism，signal transduction，transport and transcription etc.
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Discussion

• Research Hotspots and Trend Analysis of Horticulture in China
• FAN Jinfeng1 and DENG Xiuxin2,*
• Acta Horticulturae Sinica. 2019, 46(6): 1201-1214. DOI:10.16420/j.issn.0513-353x.2018-0746
• Abstract ( 527 ) HTML ( 1440 ) PDF (2790KB) ( 1440 ) 　　　
• Graduate thesis，the most representative work when the graduate obtains the degree，presents the academic discipline direction and the research characteristics of the postgraduate training units，and also shows the discipline developmental level and the industrial demands to a certain extent. Bibliometrics analysis was used to analyze the graduate thesis in horticulture collected from 1998 to 2017 in China National Knowledge Internet（CNKI）by CiteSpace software. From the perspective of graduate degree thesis，the research hotspots，trend and frontier of horticulture subjects were analyzed. The results showed that the hotspots of graduate thesis in horticulture were photosynthesis，genetic transformation，genetic diversity，fruit quality，biological characteristics and plant hormones，most of which belonging to plant physiology and molecular biology. Graduate thesis in horticulture mainly focuses on basic research，but less on application research. Research subjects selection and countermeasures of horticulture in the future were proposed in this study.
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New Cultivars

• A New Early Ripening Sweet Cherry Cultivar‘Wuyuehong’
• CHEN Long，CHENG Hehe，LI Yusheng，WU Yaqin，WU Yongjie，LI Yougang，and ZHAO Yanhua*
• Acta Horticulturae Sinica. 2019, 46(6): 1215-1216. DOI:10.16420/j.issn.0513-353x.2019-0061
• Abstract ( 970 ) HTML ( 573 ) PDF (1207KB) ( 573 ) 　　　

• ‘Wuyuehong’is a new early-ripening sweet cherry cultivar selected from the hybrid seedlings from embryo culture of‘Hongdeng’sweet cherry cultivar. The fruit is red with wide-heart shape. The average fruit weight is 9.21 g and the biggest one is 13.7 g. The flesh is pink，crisp，juicy and sweet with the soluble solids content of 18.5%. It ripens 5–7 d earlier than‘Hongdeng’in Qinhuangdao area. The tree is relatively vigorous and very adaptable to chilling and freezing injuries，the production at nine years old is 12 078 kg ? hm-2。

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• A New Okra Cultivar‘Min Qiukui 3’
• LAI Zhengfeng，LIAN Dongmei，YAO Yunfa，LIN Bizhen，and HONG Jianji*
• Acta Horticulturae Sinica. 2019, 46(6): 1217-1218. DOI:10.16420/j.issn.0513-353x.2018-0415
• Abstract ( 229 ) HTML ( 454 ) PDF (1284KB) ( 454 ) 　　　
• ‘Min Qiukui 3’is a new okra cultivar which was bred by systematic selection after crossing ‘FL-14’as female parent and‘Dongyuan 2’as male parent. The cultivar has strong growth potential，140–180 cm in height，first flower on 5–6 node. The shape of fruit is beautiful without setae. The fruit is green with 5 arrises，about 15 cm in length，1.9 cm in diameter and 25 g in weight. The fruit is not easy to age with crisp and tender taste.‘Min Qiukui 3’is an early-maturity cultivar with high temperature tolerance，water logging tolerance and strong disease resistance，and with a high yield of 39 952.5 kg ? hm-2. It is suitable to be cultivated in greenhouses and open fields in all regions of China.
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• A New Early-maturing Sweet-waxy Corn Cultivar‘Jingkenuo 2016’
• XU Li，FAN Yanli，XI Shengli，ZHANG Cuifen，ZHANG Xiaoji，DONG Hui，SHI Yaxing*，and LU Baishan*
• Acta Horticulturae Sinica. 2019, 46(6): 1219-1220. DOI:10.16420/j.issn.0513-353x.2018-0334
• Abstract ( 528 ) HTML ( 519 ) PDF (2447KB) ( 519 ) 　　　
• ‘Jingkenuo 2016’is a new excellent early-maturing sweet-waxy corn cultivar developed from the cross of‘N39’and‘Tiannuo 2’. Sweet and waxy kernels（1︰3 quantitatively）are contained on the same ear，resulting in soft and sweet-scented tastes.‘Jingkenuo 2016’contains 12.4%–13.1% soluble solids content（SSC）and 2.3563 μg ? g-1 folic acid. Its kernel is white and growth period lasts 83 days from sowing to harvesting，10 days earlier than that of‘Jingkenuo 2000’. It has high and steady yields in adaptable region with 400 g in one ear and 13.5 t ? hm-2.
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• A New Seedless Watermelon Cultivar‘Nongkeda 21’
• MA Jianxiang，ZHANG Xian*，ZHANG Yong，LI Hao，WEI Chunhua，YANG Jianqiang，YANG Xiaozhen，and XU Nana
• Acta Horticulturae Sinica. 2019, 46(6): 1221-1222. DOI:10.16420/j.issn.0513-353x.2018-0395
• Abstract ( 373 ) HTML ( 523 ) PDF (1043KB) ( 523 ) 　　　
• ‘Nongkeda 21’is a new mid-maturation seedless watermelon cultivar which was selected from the cross-combination of MD06 and F16. It is suitable to cultivate in the open field of northern China in the spring．The whole growth period of‘Nongkeda 21’is about 110 days，and the period for fruit development is around 35 days. It has a vigorous growth potential with an average single fruit weight of 6.5 kg and a yield of 52.5 t ? hm-2. The fruit shape of‘Nongkeda 21’is oval and its shape index is 1.0. The fruit skin is dark green，and the pericarp thickness is about 1.2 cm. The fruit flesh is red fine sandy. The center sugar content is 12.5%，value of that is close to the edge sugar content. More importantly，this cultivar has a high resistance to disease and other adverse stimuli.
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