Research Papers

• Overexpression of CsNBS-LRR in Citrus Confers Bacterial Canker Resistance by Regulating SA Signaling Pathway
• LI Qiang，QI Jingjing，DOU Wanfu，QIN Xiujuan，HE Yongrui*，and CHEN Shanchun*
• Acta Horticulturae Sinica. 2020, 47(5): 817-826. DOI:10.16420/j.issn.0513-353x.2019-0625
• Abstract ( 425 ) HTML ( 734 ) PDF (1493KB) ( 734 ) 　　　
• The citrus CsNBS-LRR gene was cloned and analyzed for its expression profiles induced by citrus canker and phytohormones. The function was verified by over-expression in Wanjincheng（Citrus sinensis），and further analysis was carried out for the mechanisms. The results showed that the open reading frame of CsNBS-LRR was 3 633 bp，encoding 1 210 amino acids. It was down-regulated by Xanthomonas citri subsp. citri（Xcc）in the susceptible variety Wanjincheng，and up-regulated in the resistant variety Calamondin（Citrus madurensis）. In Calamondin，CsNBS-LRR was significantly up-regulated by salicylic acid（SA），while in Wanjincheng it was slightly increased. In the two varieties，CsNBS-LRR was not significantly induced by methyl jasmonate（MeJA）. Overexpression（OE）of CsNBS-LRR significantly results in significantly enhanced resistance to citrus bacterial canker（CBC）in the transgenic lines，as revealed by the disease severity which was 75%–88% of the wild type. The salicylicacid content in the transgenic plants and the transcription level of key genes in the salicylic acid biosynthesis were significantly increased. Transcriptional levels of key genes in salicylic acid signaling pathway are also enhanced and more sensitive to the Xcc infection. Over all，CsNBS-LRR is a potential disease resistance gene of CBC，which can improve CBC resistance through the regulation of salicylic acid signaling pathway.
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• Comprehensive Evaluation and Diversity Analysis of Fruit Quality Traits in Longan‘Shuguan’בDawuyuan’Sexual Progenies
• XUE Xin1,2,3，SHI Shengyou1,2,3,*，and HOU Shikui4
• Acta Horticulturae Sinica. 2020, 47(5): 827-836. DOI:10.16420/j.issn.0513-353x.2019-0531
• Abstract ( 569 ) HTML ( 668 ) PDF (757KB) ( 668 ) 　　　
• Sixty-five individuals of longan F1 population from a cross between‘Shuguan’（female）× ‘Dawuyuan’（male）were chosen as materials，and 27 fruit quality traits of three years were collected and determined according to the method described in Shannon-weinner and Data Standard for longan（Dimocarpus longan）methods. The coefficient of variation，index and principal component were analyzed using the SPSS19.0 software. The results showed that the fruit quality traits of 65 individuals were significantly different. The coefficient of variation of 13 quantitative traits（single fruit weight，vertical diameter，transverse diameter，soluble solids content，edible rate，peel thickness，pericarp weight，flesh thickness，seed weight，vitamin C content，sucrose content，glucose content and fructose content）ranged from 6.95% to 41.64% with a diversity index ranging from 0.56–1.28. The diversity index of 14 description characters（harvest period，pericarp colour，fruit shape，fruit shoulder，fruit top，turtle crack，braided，pulp colour，flesh texture，flesh transparency，freestone，flesh juice，degree of flesh dregs and flesh flavor）ranged from 0.56 to 1.28. Meanwhile，the principal component analysis showed that the cumulative contribution rate of five traits（single fruit weight，edible rate，soluble solids content，harvest period and flesh texture）was 87.50%. In summary，a method for comprehensive evaluation of fruit quality traits of hybrids of‘Shuguan’בDawuyuan’was established in this study. Five excellent individuals（SD7，SD11，SD36，SD53 and SD120）were screened out among 65 individuals and the result was highly consistent with our observations.
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• Genome-wide Identification of the Laccase Gene Family and Its Expression Analysis Under Low Temperature Stress in Musa accuminata
• LIU Yanying，NI Shanshan，XIANG Leilei，CHEN Yukun，and LAI Zhongxiong*
• Acta Horticulturae Sinica. 2020, 47(5): 837-852. DOI:10.16420/j.issn.0513-353x.2019-0626
• Abstract ( 361 ) HTML ( 715 ) PDF (2680KB) ( 715 ) 　　　
• Laccase has been shown a multifunctional enzyme that plays many important roles. The whole genome-wide of identification of banana laccase family members was conducted and analyzed. Using bioinformatics approaches，22 laccase genes（MaLAC）were identified from Musa acuminata genome and 11 laccase genes（MbLAC）were also identified from Musa balbisiana genome. Most of MaLAC and MbLAC members contained three typical Cu-oxidase domains. Gene structure analysis showed that most of MaLACs and MbLACs were composed of five introns and six exons. Phylogenetic clustering analysis indicated that the MaLACs were divided into five groups and the MbLACs were divided into four groups. The promoter cis-acting elements showed that the MaLAC promoter sequence contained a large number of stress response elements，such as light response，hormone response and abiotic stress，etc. The results of qRT-PCR analysis showed that the expression of some members of MaLACs increased under low temperature stress. The expression of MaLAC3-2，MaLAC4，MaLAC4-5，and MaLAC17 increased significantly at low temperatures of 13 ℃，4 ℃ and 0 ℃. Moreover，18 MaLAC transcripts were found to be potential targets of miR397 or miR408.
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• Genetic Diversity of Malus prunifolia Germplasms Based on Chloroplast DNA Analysis
• GAO Yuan，WANG Dajiang，WANG Kun*，CONG Peihua*，ZHANG Caixia，LI Lianwen，and PIAO Jicheng
• Acta Horticulturae Sinica. 2020, 47(5): 853-863. DOI:10.16420/j.issn.0513-353x.2019-0609
• Abstract ( 271 ) HTML ( 464 ) PDF (737KB) ( 464 ) 　　　
• Four intergenic region，trnH-psbA，trnS-trnG spacer + intron，trnT-5′trnL and 5′trnL-trnF of 49 accessions of newly collected germplasms of Malus prunifolia（Willd.）Borkh. were amplified by four primers. Based on genetic variation of 4 chloroplast intergenic regions，the genetic diversity of Malus prunifolia among different populations were explored from the perspective of maternal inheritance. The results showed that the length of four intergenic regions of chloroplast DNA was 3 790 bp after sequencing，splicing，alignment and merging，and 173 variable sites were detected including 2 singleton variable sites，20 parsimony informative sites and 151 insertion/deletion gaps. Among the 49 accessions of Malus prunifolia，the number of variable sites of region trnH-psbA，trnS-trnG spacer + intron，trnT-5′trnL and 5′trnL-trnF were 26，25，120 and 2. The number of haplotypes for four regions being were 9，7，8 and 3. After four regions being merged the haplotypes of chloroplast DNA fragments were 14. The region with the highest nucleotide and haplotype diversity was trnH-psbA（Hd = 0.775，Pi = 0.02143），and the nucleotide andhaplotype diversity of 5′trnL-trnF was the lowest（Hd = 0.481，Pi = 0.00072）. The cpDNA diversity of Malus prunifolia with four chloroplast DNA regionsmerged was high（Hd = 0.854，Pi = 0.00949）. Tajima’s test showed all Tajima’s D values were not significant at P > 0.10，which indicated that variation of those chloroplast regions followed neutral theory of molecular evolution. The genetic variation of Malus prunifolia mainly existed within populations. Gene exchange among different populations is frequent，and genetic differentiation among most of populations is less，which has little relationship with geographical distance.
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• Distribution of orf687，a Fertility Restorer Gene for Ogura CMS in Radish
• ZHANG Li*，WANG Qingbiao，and WANG Yanping
• Acta Horticulturae Sinica. 2020, 47(5): 864-874. DOI:10.16420/j.issn.0513-353x.2019-0819
• Abstract ( 197 ) HTML ( 385 ) PDF (954KB) ( 385 ) 　　　
• The distribution of orf687（Rfo），a fertility restorer gene of Ogura CMS，was investigated in 129 radish cultivars，including 5 cultivated species and 4 wild species. Our results showed that orf687 was widely distributed in East Asian big radish（89.16%），European small radish（85.71%），black radish （100%），pod radish（100%）and wild radish（70%）. Among East Asian big radish，95.45% of the red-skinned radish contained orf687，which was higher than that of white radish and green radish. In addition，genotype identification of orf687 by PCR-RFLP showed that the ratio of double recessive genotype（rfrf）without restoring ability was the highest in wild radish（57.14%），followed by East Asia big radish（47.13%）and European small radish（37.50%）. Moreover，in East Asian big radish，the ratio of red-skinned varieties with rfrf genotype was 76.19%，higher than that of white radish（41.67%）and green radish（23.53%）. The results clarified the Rfo genotypes of different radish varieties，and will provide guidance for the breeding and utilization of male sterile lines.
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• Identification of MYB Family Genes and Its Relationship with Pungency of Pepper
• JU Lixiang，LEI Xin，ZHAO Chengzhi，SHU Huangying，WANG Zhiwei，and CHENG Shanhan*
• Acta Horticulturae Sinica. 2020, 47(5): 875-892. DOI:10.16420/j.issn.0513-353x.2019-0735
• Abstract ( 527 ) HTML ( 866 ) PDF (4288KB) ( 866 ) 　　　
• One hundred and seventy-two MYB transcription factors were extracted from the pepper genome database by bioinformatics methods，and there was a comprehensive analysis of the sequence characteristics，the chromosomal location，evolutionary relationships，protein conservative motif and genetic structure at the same time. What’s more，the technology of RNA-seq was used to screen MYB genes that might be related to the expression of spiciness genes. The results showed that there were 1R，2R（R2R3），3R，6R and other types of pepper MYB，among which R2R3 was the majority. Furthermore structural domain analysis showed that they have typical W type R2R3 conservative motifs. Subsequently，about twenty motif elements were obtained，and position analysis showed that MYB proteins from the same branch seem to have similar structural characteristics. A total of 37 groups were obtained through clustering with Arabidopsis thaliana，suggesting that the pepper MYBs may have various biological functions. The RNA-seq results indicated that the expression of twelve MYB，such as CaMYB98 and CaMYB168，were consistent with the accumulation of capsaicin content in fruit placenta tissues of‘Huangmowang’at different development stages. Thus it was predicted that they can regulate the metabolic pathwayof capsaicin by up- or down-regulating the expression of related proteins by binding to specific sites，which can be further studied as important candidate genes for the regulation of pungency.
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• Pollen Morphology of Impatiens sect. Impatiens（Balsaminaceae）
• WANG Qian1,2,3，YANG Xudong2,4,5，XIA Changying1,3,4，LI Jin4,5，and YU Shengxiang4,5,*
• Acta Horticulturae Sinica. 2020, 47(5): 893-906. DOI:10.16420/j.issn.0513-353x.2019-0426
• Abstract ( 317 ) HTML ( 603 ) PDF (13377KB) ( 603 ) 　　　
• To study the taxonomic value and systematic implications of the pollen morphology of sect. Impatiens，30 species from this section were studied by Scanning Electron Microscope. The results indicated that the morphological characteristics of the pollen grains are generally shown as follows：single and 4-colpate pollen grains are mostly oblong，germinal furrow are horned，the exine of pollen grains are of reticulate ornamentation. In addition，pollens of different species have significant differences in size， polar shape，muri shape，lumen size and the density of granular appendages in the lumen. For example，polar shape is mostly oblong，occasionally，there are also sub-rounded and sub-quadrate. Lumina on the surface of pollen distributed in two types：even and uneven. The muri of lumen are smooth or sinuate towards margin. There are granular appendages in the lumina with different densities. Based on above characteristics，the pollen of sect. Impatiens was divided into two types and eight subtypes. This study indicated that the morphological characteristics of pollen，especially if the lumen is even，muri shape，lumen size，and granules density in the lumen，could be used as the basis for classification of sect. Impatiens and the definition of species level.
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• Induction of Embryogenic Calli from Immature Pedicels and Efficient Plant Regeneration of Hippeastrum
• YU Bo1，HUANG Lili1，ZHU Yu2，ZHU Genfa1，and SUN Yingbo1,*
• Acta Horticulturae Sinica. 2020, 47(5): 907-915. DOI:10.16420/j.issn.0513-353x.2019-0672
• Abstract ( 457 ) HTML ( 483 ) PDF (2757KB) ( 483 ) 　　　
• The aim of this study was to establish an efficient system of plantlet regeneration and seedling production for Hippeastrum. We focused on embryogenic calli induction from immature pedicel explants and plantlet regeneration. The effects of plant growth regulator concentration，the developmental period of the explant，and explant size were evaluated. The highest induction rate of embryogenic calli（85.3%）was achieved by culturing 1 mm thick slices of immature pedicel explants on Murashige and Skoog（MS）medium supplemented with 0.5 mg ? L-1 N-phenyl-N’-1,2,3-thiadiazol-5-ylurea（TDZ）and 2.0 mg ? L-1 2,4-dichlorophenoxyacetic acid（2,4-D）for 8 weeks. Embryogenic calli were subcultured on the same medium and were subcultured once a month. Under these conditions，the proliferation rate of embryogenic calli was 10.6-fold per month. The plant regeneration rate of embryogenic calli reached 98.0%，and an average of 12.3 plantlets formed from each embryonic callus on MS medium without any growth regulators. After subculturing 36 times（3 years），there were no significant changes in embryogenic calli proliferation and plant regeneration efficiency. The survival percentage of these seedlings hardened in the greenhouse was 97.5%. After transplanting into the field，no obvious phenotypic variations were observed among the regenerated plants. Inter-simple sequence repeat（ISSR）marker analysis supported the absence of DNA-level variations among the regenerated plants.
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• Subcellular Distribution and Responses of Antioxidant Systems in Leaves of Three Rhododendron Cultivars Under Alkali Stress
• LIU Pan，GENG Xingmin*，and ZHAO Hui
• Acta Horticulturae Sinica. 2020, 47(5): 916-926. DOI:10.16420/j.issn.0513-353x.2019-0314
• Abstract ( 304 ) HTML ( 455 ) PDF (736KB) ( 455 ) 　　　
• In order to explore the alkali-resistant mechanism of Rhododendron，the seedlings of the three Rhododendron cultivars，‘Yanzhimi’，‘Hongshanhu’and‘Hongyue’were treated with mixed NaHCO3 and Na2CO3 for 2 months. The morphological changes of the seedlings under alkali stress were observed，and ROS and antioxidant systems in the chloroplasts，mitochondria and cytosol of the leaves were determined. The results showed that the alkali tolerance of the three cultivars from high to low was ‘Yanzhimi’>‘Hongshanhu’>‘Hongyue’according to the alkali damage index. Under alkali stress，the H2O2 and superoxide anion levels in the three subcellular fractions of the three cultivars were significantly increased，which resulted in the increase in MDA content. There were differences in the activity of antioxidant enzymes among the three cultivars under alkali stress. SOD，POD，CAT and GR activities in the three subcellular fractions of‘Yanzhimi’were markedly increased after alkali stress，and the significant increase of APX activity in the chloroplasts and cytosol was observed in the chloroplasts and cytosol，but not in the mitochondria. Under alkali stress，the activities of CAT and APX in the chloroplasts，SOD，POD and CAT in the mitochondria and SOD，POD，and CAT in the cytosol of‘Hongshanhu’were significantly increased. SOD activity of‘Hongyue’increased significantly in the mitochondria and cytosol，CAT activity increased significantly in chloroplasts and mitochondria，POD and APX activities decreased significantly，GR activity did not change significantly. The contents of non-enzymatic antioxidants，AsA and GSH in the chloroplasts of the three cultivars decreased，and increased in the mitochondria and cytosols under alkali stress. Under alkali stress，the contents of non-enzymatic antioxidants AsA and GSH in the three Rhododendron cultivars decreased in chloroplasts and increased in mitochondria and cytosol.‘Yanzhimi’with the stronger tolerance maintained relatively more stable ROS level and lower MDA content and higher SOD，POD，APX and GR activities than the other two cultivars under alkali stress. ROS and antioxidant systems in the three subcellular fractions，chloroplasts，mitochondria and cytosol were determined and found that the levels of H2O2 and superoxide anion in the cytosol were significantly higher than that in the mitochondria and chloroplasts，corresponding antioxidant enzymes SOD，POD and GR and antioxidants AsA and GSH were mainly distributed in the cytosol，subcellular distribution of ROS and antioxidant systems had higher consistency. APX was mainly distributed in the chloroplasts. CAT was the most active in the mitochondria. The results indicated that ROS accumulation in the different subcellular fractions and their peroxidative damage degree varied under alkali stress，and the responses of the antioxidant defense systems in each subcellular fraction to alkali stress were also different. Cytosol was the main subcellular fraction where ROS were generated and removed.
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• Comparison of Tea Plant Volatiles Exogenously Induced by Jasmonates or Salicylates Elicitors
• JIAO Long1,2，BIAN Lei1，LUO Zongxiu1，LI Zhaoqun1，XIN Zhaojun1，XIU Chunli1，CAI Xiaoming1,*，and CHEN Zongmao1,*
• Acta Horticulturae Sinica. 2020, 47(5): 927-938. DOI:10.16420/j.issn.0513-353x.2019-0803
• Abstract ( 369 ) HTML ( 518 ) PDF (1438KB) ( 518 ) 　　　
• To compare the tea plant volatiles induced by jasmonates or salicylates elicitors，four elicitors including jasmonic acid（JA），methyl jasmonate（MeJA），salicylic acid（SA）and methyl salicylate（MeSA），were respectively sprayed on tea plants，and tea plant volatiles were collected and analyzed by dynamic headspace technique and gas chromatography-mass spectrometer，respectively. The four elicitors could increase the emission amount and component number of tea plant volatiles. The control tea plant only released two compounds，and the emission amount was lower than 0.01 ng ? h-1 ? g-1. JA could induce nine volatile compounds，and the total emission amount could be up to 4.37 ng ? h-1 ? g-1，of which terpenes and aromatic compounds，such as (E)-β-ocimene，(E)-4,8-dimethyl-1,3,7-nonatriene（DMNT）and benzeneacetaldehyde，accounted for more than 80%. MeJA could induce twenty-seven volatile compounds，and the total amount could be up to 95.41 ng ? h-1 ? g-1，of which only terpenes，such as (E)-β- ocimene，DMNT and (E,E)-α-farnesene，accounted for more than 80%. Three aromatic components，including anisole，phenol and MeSA，could be induced by SA. Emission amount of the three compounds could be up to 191.21 ng ? h-1 ? g-1，of which MeSA made up more than 90%. MeSA was the only component of the volatiles induced by MeSA，and the emission amount of MeSA could be up to 507.5 ng ? h-1 ? g-1. By increasing the concentration of applied elicitors，the emission amount of main components or the component number of the induced volatiles were increased. The principal component analysis and hierarchical cluster analysis showed that the scores of the induced volatiles were significantly different among the four elicitors，but the volatiles induced by JA and MeJA and those induced by SA and MeSA were clustered into one class，respectively. In conclusion，exogenously application of JA，MeJA，SA and MeSA could remarkably increase the emission of tea plant volatiles，the volatiles induced by jasmonates and salicylates elicitors were distinctly different，but the volatiles induced by the same kind of elicitors were similar. It is of great significance to research the physiological mechanism and anti-herbivores function of tea plants induced by JAs and SAs.
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Research Notes

• Cloning and cis-acting Element Analysis of CCD1 and CCD4 Promoter in Apricot
• FENG Jing1，YANG Can1，LU Juanfang1，and XI Wanpeng1,2,*
• Acta Horticulturae Sinica. 2020, 47(5): 939-952. DOI:10.16420/j.issn.0513-353x.2019-0610
• Abstract ( 307 ) HTML ( 745 ) PDF (3068KB) ( 745 ) 　　　
• The promoters of pPaCCD1 and pPaCCD4 were cloned by genomic walking method using the CCD1 and CCD4 gene fragments in the transcriptome database. Sequencing showed that the lengths of pPaCCD1 and pPaCCD4 promoter were 2 233 bp and 1 838 bp，respectively. The cis-acting elements of promoter were analyzed and predicted using PlantCare databases. The results showed that two promoters contain multiple cis-acting elements associated with light signal，abscisic acid，and methyl jasmonate. In addition，the PaCCD1 promoter contains gibberellin，low temperature and transcription enhancer elements. The results suggested that the expression of PaCCD1 and PaCCD4 may be regulated by light signaling，plant hormone and stress. To further define two promoters’ core regions，two promoter-reporter vectors were respectively constructed based on structural characters of promoters and distributions of controlling elements in promoter using the promoter deletion mutation，and the vectors were fused to GUS gene and then were transformed into tobacco leaves. The efficient cis-acting element of PaCCD1 was included in–2 174 to–1 700 bp，–1 700 to–1 200 bp，–1 200 to–600 bp，while the efficient cis-acting element of PaCCD4 was included in–1 740 to–1 200 bp，–1 200 to–600 bp.The GUS enzyme activity of PaCCD1 and PaCCD4 was gradually weakened with the deletion of the promoter fragment. These results revealed that the core regions of the PaCCD1 and PaCCD4 promoter were within –1 200 to 2 174 bp and–1 200 to–1 740 bp，respectively.
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• Investigation of Melatonin on Somatic Embryo Induction for‘Thompson Seedless’Grapevine
• YA Rong1，XU Weirong2,3,4,5,*，ZHANG Ying1，XIA Siqi2，and ZHANG Ningbo2,3,5
• Acta Horticulturae Sinica. 2020, 47(5): 953-962. DOI:10.16420/j.issn.0513-353x.2019-0958
• Abstract ( 291 ) HTML ( 554 ) PDF (2543KB) ( 554 ) 　　　
• The effects of different concentrations of melatonin（0，1.0，2.0，3.0 mg ? L-1）on the induction efficiency in Vitis vinifera‘Thompson Seedless’via somatic embryogenesis were investigated with unopened flower buds as explants. The results showed that the callus induction rate was 73.67%–89.10% when subcultured on the medium of MS + 1.0–3.0 mg ? L-1 melatonin + 2.0 mg ? L-1 6-BA + 30 g ? L-1 sucrose + 3 g ? L-1 phytagel for 30 days，which was significantly higher than that of 2,4-D treatment. Concurrently，the callus formation time on the above-mentioned medium was shortened by 14 days compared to the corresponding control medium with 2,4-D. At 120 days after callus induction，somatic embryos appeared in different concentrations of melatonin，among which the highest incidence was on themedium of MS + 1.0 mg ? L-1 melatonin + 2.0 mg ? L-1 6-BA + 30 g ? L-1sucrose，reaching 12.05% at 180 d. After 30 days of germination，the cotyledon embryos on X6 medium with MS + 60 g ? L-1 sucrose + 0.5 g ? L-1 activated carbon were transferred to the seedling medium with MS + 0.2 mg ? L-1 6-BA + 0.1 mg ? L-1 NOA + 30 g ? L-1 sucrose + 0.5 g ? L-1 activated carbon. Among them，1.0 mg ? L-1 melatonin induced a large number of normal somatic embryogenesis，and the induction rate was 14.84%. The results also demonstrated that the induction rate of somatic embryos treated with different concentrations of melatonin increased rapidly after 180 d，and low concentrations of melatonin was beneficial to somatic embryos germination and normal development，whereas the 2,4-D-induced callus had no somatic embryos formation.
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• Identification of CRK Gene Family in Pear and Its Members in Response to Signals of Valsa pyri
• LIU He，DUO Hu，ZHAO Dan，SUN E，MA Fupeng，MA Chunling，and ZUO Cunwu*
• Acta Horticulturae Sinica. 2020, 47(5): 963-973. DOI:10.16420/j.issn.0513-353x.2019-0759
• Abstract ( 268 ) HTML ( 583 ) PDF (2371KB) ( 583 ) 　　　
• The Cysteine-rich receptor like kinases（CRKs）took important regulatory roles during plant：PF01657）and kinase（Pfam：PF00069），a genome-wide identification of CRKs in pear（Pyrus spp.）genome were performed. In addition，the physical and chemical characteristics，evolutionary characteristics，subcellular location，chromosomal distribution，cis-acting regulatory element（cis-element）and expression patterns were analyzed. A total of 32 CRKs were obtained，with the amino acid size from 440 to 1 217 aa，molecular weight of 48.90–137.02 kD，and isoelectric point of 5.31–8.59. CRKs were predicted mainly located on plasma membrane. According to evolutionary analysis，a total of 156 CRKs from 5 plant species，including pear，Arabidopsis thaliana，apple，tomato and rice，could be divided into 6 subgroups. Pear CRKs were mainly distributed in subgroup Ⅳ，Ⅴand Ⅵ. In pear CRKs，5 tandem duplicated gene clusters，including 20 members，were found. For all the family members，a large number of cis-elements responsive to hormone and stress were discovered in promote regions. After inoculated Valsa canker pathogen Valsa pyri（Vp），8 and 10 CRKs were differentially expressed in Pyrus betulifolia （resistant）and‘Zaosu’pear（Pyrus bretschneideri，susceptible），expression of 6 members were changed in both two germplasm. Among these，Pbr001477.1 and Pbr000205.4 were up-regulated in two germplasm，but other genes exhibited distinct expressions between two germplasm.
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• Genetic and QTL Mapping Analysis of Bolting Time in Cabbage（Brassica oleracea）
• WANG Wuhong，WANG Jinglei，LI Biyuan，WEI Qingzhen，HU Tianhua，HU Haijiao，and BAO Chonglai*
• Acta Horticulturae Sinica. 2020, 47(5): 974-982. DOI:10.16420/j.issn.0513-353x.2019-0825
• Abstract ( 319 ) HTML ( 455 ) PDF (1640KB) ( 455 ) 　　　
• We constructed the populations of F1，BC1，BC2，and F2 by using cabbage lines‘S-1’（early flower）and‘G-1’（late flower）as parents and adopted the plant quantitative trait major gene + polygenic mixed genetic model method to analysis the genetic model of bolting time of cabbage. Besides，we used SLAF-BSA technology to mapping the bolting time QTLs. The results showed that the bolting time fitted the model of two additive-dominant-epistatic major genes and additive-dominance polygenes. The average heritability of major genes plus polygenes was 93.41%，which indicated that bolting trait of cabbage was mainly affected by major gene inheritance. Moreover，two QTLs were detected，which located on chromosome C02 2.31–3.09 Mb and 33.57–34.40 Mb，respectively，with a total length of 1.61 Mb.
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• Cloning and Expression Analysis under Abiotic Stress of the DHAR Gene in Camellia sinensis
• LIU Jingyu*，TENG Ruimin*，LI Hui，LIU Hao，and ZHUANG Jing**
• Acta Horticulturae Sinica. 2020, 47(5): 983-994. DOI:10.16420/j.issn.0513-353x.2019-0684
• Abstract ( 223 ) HTML ( 450 ) PDF (1858KB) ( 450 ) 　　　
• Using RT-PCR technology，the CsDHAR gene encoding dehydroascorbate reductase was cloned from the cDNA of Camellia sinensis‘Longjing 43’. CsDHAR gene was 639 bp in length，encoding 212 amino acids，belonging to glutathione transferase superfamily which is highly conservative. Phylogenetic analysis showed that CsDHAR protein was closely related to Arabidopsis DHAR1 and DHAR2. Among different species，CsDHAR protein was closely related to Populus trichocarpa and P. euphratica. Physicochemical analysis showed that CsDHAR protein was a hydrophilic protein. Structural analysis showed that CsDHAR protein has a typical functional domain，and the tertiary structure is mainly composed of alpha-helix and irregular curl. Quantitative real-time PCR analysis showed that CsDHAR expression levels were not significantly different at different growth stages in leaves of tea plant. CsDHAR gene expression profiles of C. sinensis‘Longjing 43’and‘Anji Baicha’were detected and analyzed by qRT-PCR.‘Longjing 43’had the highest expression level in 4 h under low and high temperature treatments，and the highest expression level in 24 h under drought and high salt treatments. The expression level of‘Anji Baicha’was the highest in 4 h under high temperature and high salt treatments，and the highest expression level in 2 h under drought treatment. Under different abiotic stress treatments，CsDHAR was induced，indicating that the gene was involved in the regulation process of stress response in tea plant.
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Review

• Research Advances of Citrus microRNAs in Plant Development and Stress Resistance
• YAO Lixiao，HE Yongrui，and CHEN Shanchun*
• Acta Horticulturae Sinica. 2020, 47(5): 995-1008. DOI:10.16420/j.issn.0513-353x.2019-0552
• Abstract ( 361 ) HTML ( 626 ) PDF (842KB) ( 626 ) 　　　
• microRNAs（miRNAs）are a class of endogenous small non-coding RNAs，which regulate complementary mRNAs by mediating mRNA degradation and translational repression. The research on citrus miRNAs has been conducted from 2005，three years after the first plant miRNA was identified in Arabidopsis. Many plant-conserved miRNAs and novel miRNAs have been identified in citrus，with the advancement of high-throughput sequencing technology and the improvement of bioinformatics analysis methods. These miRNAs were not only involved in the biological processes，such as citrus reproduction，flower and fruit development，but also in the resistance against biotic and abiotic stresses，through regulation of their target genes. Meanwhile，the functions of cis-miR156，cis-miR396，and cis-miR3954were summarized herein. In the present manuscript，we also prospected the usage of citrus-specific viral vectors and CRISPR/Cas9 gene editing technology to accelerate the study on function of citrus miRNAs，especially the novel miRNAs.
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New Cultivars

• A New Triploid Pear Cultivar‘Huaxiangsu’
• ZHANG Ying1，CAO Yufen1,*，TIAN Luming1，DONG Xingguang1，HUO Hongliang1，LI Shuling2, HUANG Lisen1，ZHAO Deying1，QI Dan1，XU Jiayu1，YAN Shuai1，and WANG Lidong1
• Acta Horticulturae Sinica. 2020, 47(5): 1009-1010. DOI:10.16420/j.issn.0513-353x.2019-0074
• Abstract ( 250 ) HTML ( 439 ) PDF (904KB) ( 439 ) 　　　
• ‘Huaxiangsu’is a triploid pear cultivar resulted from crossing between‘Sha 01’and ‘Naguoli’. The tree is vigorous and spreading. The average weight per fruit is 180 g. The fruit is characterized by obovate shape，yellowish-green skin covered with occasional red blush toward the sun，milky white flesh，crisp，fine texture，juicy，high quality with sweet，slight aromatic flavour and good storability. The soluble solids content is 13.54% and the titrable acid content is 0.13%. The fruits ripen in mid-September in Xingcheng City，Liaoning Province. The developmental period of pear extends up to 140 days from fruit set. The production in full fruit period is 39 000 kg ? hm-2. It’s more resistant to cold and pear scab.
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• A New Auricularia cornea Cultivar‘Shener 1’
• YU Hailong1,2,*，ZHANG Meiyan1,*，Shen Xiufen1,2，ZHANG Lujun1，SHANG Xiaodong1，LI Yu2，and TAN Qi1,**
• Acta Horticulturae Sinica. 2020, 47(5): 1011-1012. DOI:10.16420/j.issn.0513-353x.2019-0154
• Abstract ( 169 ) HTML ( 325 ) PDF (3110KB) ( 325 ) 　　　
• ‘Shener 1’was domesticated by wild Auricularia cornea which was gathered from Chifeng County，Inner Mongolia in 2007. The cultivar is characterized by short life circle，large number of primordium，high yield. The fruiting-body is moderate size，ear like，elasticity，glutinous，and it has moderate size，glaze surface，good elasticity. The cultivar is suitable to sale fresh products.
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• A New Hericium erinaceus Cultivar‘Huhou 8’
• LI Qiaozhen1,*，LI Zhengpeng1,*，ZHANG Henan1，WU Di1，YU Hailong1，ZHANG Yinfang2，and YANG Yan1,**
• Acta Horticulturae Sinica. 2020, 47(5): 1013-1014. DOI:10.16420/j.issn.0513-353x.2018-1046
• Abstract ( 358 ) HTML ( 441 ) PDF (1244KB) ( 441 ) 　　　
• ‘Huhou 8’is new cultivar of edible mushroom（Hericium erinaceus）by crossing‘0605’and‘Cichang’. It has a good taste，high yield and suitable for protected cultivation. The mycelium growth potential was strong. The fruiting bodies were solitary，hard fleshy and compact. Its average length is 10.2 cm，average width is 7.8 cm and average height is 6.2 cm. The growth cycle is short and biological efficiency is 44% for the first tide. The temperature is 14–18 ℃ during mushroom period. It has strong resistance.
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• A New Magnolia Cultivar‘Xiaoxuan’
• XIE Bin，WANG Yaling*，and YE Wei
• Acta Horticulturae Sinica. 2020, 47(5): 1015-1016. DOI:10.16420/j.issn.0513-353x.2019-0039
• Abstract ( 329 ) HTML ( 310 ) PDF (1374KB) ( 310 ) 　　　
• Magnolia‘Xiaoxuan’is a new cultivar which is hybridized by Magnolia stellata ‘Waterlily’and Michelia platypetala‘Xin Hanxiao’. The seedling of‘Xiaoxuan’ is obtained by artificial hybridization. The seedling is grafted on root stocks，Magnolia denudata Desr.，Magnolia biondii Pamp. and Michelia champaca L. are selected as the root stocks. The plant type is compact with dense branches，leaves and large amount of flowers. The color of floral back is red to pink. The flower blooms in two seasons with long flowering period. The cultivar with high ornamental value can be planted widely.
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• A New Zelkova schneideriana Cultivar‘Linyuan’
• HU Xijun1,*，JIN Xiaoling1,2，XING Wen1，WANG Xiaoli1，and ZHANG Yaping1,3
• Acta Horticulturae Sinica. 2020, 47(5): 1017-1018. DOI:10.16420/j.issn.0513-353x.2019-0020
• Abstract ( 210 ) HTML ( 268 ) PDF (1328KB) ( 268 ) 　　　
• A new Zelkova schneideriana cultivar‘Linyuan’was selected from the seedling. The main characteristics are nearly spherical tree shape，long branches，large and broad oval mature leaves. It sprout early in spring and leaf color turns red-brown in early autumn. The cultivar has good drought and salinity tolerance. It has high survival rate of grafting propagation and can be cultivated in the hills and plains south of the Yangtze River.‘Linyuan’is the optimum tree species for urban street trees，and planting in arid and barren areas.
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