Research Papers

• Screening and Identification of Bacillus velezensis XC1 and Its Influence on Apple Replant Disease
• YAN Zhubing, WANG Mei, MING Changjun, JIANG Yuanmao, SHEN Xiang, CHEN Xuesen, YIN Chengmiao, MAO Zhiquan
• Acta Horticulturae Sinica. 2021, 48(3): 409-420. DOI:10.16420/j.issn.0513-353x.2020-0476
• Abstract ( 986 ) HTML ( 582 ) PDF (1624KB) ( 582 ) 　　　

• In this study,a strain XC1 was screened from the rhizosphere soil of healthy apple trees in the replanted apple orchard,which could antagonize the main pathogenic fungi（Fusarium solani,F. proliferatum,F. oxysporum,F. moniliforme）of apple replant disease. Among them,the inhibitory rate of F. oxysporumwas the highest,reaching 79.83%. Through morphological,physiological and biochemical characteristics,16S rDNA and gyrA sequence analysis,the bacterium was identified as Bacillus velezensis,which is a new biocontrol bacterium with development potential. At present,strain XC1 has been collected by the China General Microbiological Culture Collection Center,with the preservation number CGMCC No.20057. The pot experiment showed that compared with the control（replanted soil）,XC1 treatment could significantly promote the seedlings growth of Malus hupehensisRehd. and its plant height,ground diameter,fresh and dry mass were 54.8%,34.8%,121.1% and 96.0% higher than those of the control respectively;the activities of sucrase,urease,catalase and neutral phosphatase in the replanted soil treated with XC1 fertilizer were significantly increased,which were 1.57,2.71,1.21 and 1.79 times higher than those of the control,respectively. The number of fungi in the soil were significantly reduced;and the number of bacteria and actinomycetes was increased;and the gene copy number of F. oxysporum treated with XC1 fertilizer was 76.4% lower than that of the control. This indicated that B. velezensis has obvious bacteriostatic effect,which can improve the soil environment,promote the growth of M. hupehensisRehd. seedlings,and reduce the apple replant disease to a certain extent.

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• Relationship Between Morphogenesis and Carbohydrate Synthesis of the Calyx-Persistence Fruit and Calyx-shedding Fruit in Differentiation Stage of‘Dangshan Suli’Pear
• JIA Bing, GUO Guoling, WANG Youyu, WEI Pengfei, YU Tao, CHANG Xiao, HENG Wei
• Acta Horticulturae Sinica. 2021, 48(3): 421-438. DOI:10.16420/j.issn.0513-353x.2020-0602
• Abstract ( 484 ) HTML ( 385 ) PDF (1529KB) ( 385 ) 　　　

• Pyrus bretschneideri‘Dangshan Suli’was used as the experiment material,sprayed with distilled water,200 mg·L^-1 PP₃₃₃ and 400 mg·L^-1 GA₃ at full bloom stage;the calyx-persistence fruit and calyx-shedding fruit were respectively collected at the young fruit differentiation stage;the single fruit weight,chlorophyll,sorbitol,sucrose,glucose and fructose content were measured and the expression of genes related to photosynthesis,sorbitol and sucrose metabolism was analyzed by quantitative real-time PCR（qRT-PCR）. Besides,the enzyme activities of S6PDH,NAD⁺-SDH,NADP⁺-SDH,SPS and SUS were determined. The results showed that the contents of sorbitol and sucrose in calyx-persistence fruit were significantly higher than those in calyx-shedding fruit of all treatments. In terms of the autologous photosynthesis,the significantly increase sorbitol and sucrose content in all calyx-persistence fruit could be supported by the obvious higher relative expression of PSII protein subunits psbD and Rubisco activase genes in calyx-persistence fruit than those in calyx-shedding fruit. From the perspective of sorbitol synthesis pathway,the prominent higher sorbitol content in calyx-persistence fruit was related to the higher expression of S6PDH1 and the outstanding higher activity of sorbitol-6-phosphate dehydrogenase. From the perspective of ‘source-sink’transport,it was related to the distinct higher expression of sorbitol transporter genes SOT3/4/8/14/15/2/25/29/30/31/34 in calyx-persistence fruit than that in calyx-shedding fruit. Likewise,the apparent increased sucrose content in calyx-persistence fruit was related to the significant higher expression of sucrose phosphate synthase genes SPS1 and SPS8,sucrose synthase genes SUS1/3/12/13/15/17,and their clear higher enzyme activities from the perspective of sucrose synthesis pathway. When it comes to the perspective of sucrose transport pathway,it was related to distinct higher expression of the sucrose transport genes SUT1/2/3and the tonoplast monosaccharide transporter TMT2/3/4in calyx-persistence fruit. This experiment preliminary clarified that the morphogenesis of calyx-persistence fruit and calyx-shedding fruit is determined by the relative sorbitol and sucrose metabolism activities.

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• Indentification and Expression Analysis of Trihelix Transcription Factor Family in Pear
• HAN Wenlong, ZHU Zhen, LI Junru, CHEN Tianzhe, LI Guohui, SU Xueqiang, JIN Qin, CHENG Xi, CAI Yongping
• Acta Horticulturae Sinica. 2021, 48(3): 439-455. DOI:10.16420/j.issn.0513-353x.2020-0421
• Abstract ( 459 ) HTML ( 537 ) PDF (8577KB) ( 537 ) 　　　

• Trihelix transcription factors（TFs）binded to light-responsive GT elements are called GT transcription factors. This study not only identified 16 members of the Trihelix family from the pear genome,named PbGT1-PbGT16 in turn,but also identified 11 and 16 members of the Trihelix family respectively from the genomes of strawberry and peach belonging to the Rosaceae family like pear. Chromosome localization showed that the Trihelix family members of pear,strawberry and peach were distributed on 12,6 and 8 chromosomes,respectively. Segmental duplication events were found in the Trihelix family of pear by gene duplication events analysis. The clustering result of interspecific phylogenetic tree showed that the Trihelix family members of pear,strawberry and peach were divided into six subfamilies and the Trihelix family members of pear（PbGTs） belong to the GT-2,Subfamily O and SIP1 subfamilies. Combined with evolutionary relationship and qRT-PCR verification,PbGT15 may be involved in regulating lignification of pear fruit stone cells.

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• Inhibition of Pear Anthocyanin Synthesis by the PcHB12 Gene in European Pears
• ZHANG Zhen, LI Chenzhiyu, ZHANG Ya, LI Xi, WANG Shuo, WANG Xinyu, CHEN Xuesen, FENG Shouqian
• Acta Horticulturae Sinica. 2021, 48(3): 456-464. DOI:10.16420/j.issn.0513-353x.2020-0499
• Abstract ( 556 ) HTML ( 418 ) PDF (1427KB) ( 418 ) 　　　

• In order to understand the mechanism that the HD-ZipⅠtranscription factor regulates anthocyanin synthesis in pears,the European pear cultivar‘Red Clapp Favorite’was used as study material to clonePcHB12（GenBank accession number:XM_009363028）from the HD-ZipⅠfamily. Phylogenetic tree analysis,qRT-PCR,yeast one-hybrid assay,EMSA,and luciferase reporter assay were employed to study the regulatory function ofPcHB12on anthocyanin synthesis. The results showed that the open reading frame of PcHB12 is 696 bp,encoding 231 amino acids,and the predicted molecular weight of the protein is 26.77 kD. Phylogenetic tree analysis showed that PcHB12 has the highest similarity to the AtHB12 protein sequence of Arabidopsis thaliana. The expression level of PcHB12 in‘Clapp Favorite’is significantly higher than that in its red bud mutation cultivar‘Red Clapp Favorite’. In contrast,anthocyanin content and the expression levels of anthocyanin-related genesPcMYB10.1 and PcUFGT in ‘Clapp Favorite’were significantly lower than that in‘Red Clapp Favorite’. Yeast one-hybrid and electrophoretic mobility shift assay（EMSA）experiments found that PcHB12 binds to the MBS sequence in the PcMYB10.1 promoter. Luciferase experiments showed that PcHB12 negatively regulates transcription activity on the PcMYB10.1 promoter. Therefore,PcHB12 may negatively regulate PcMYB10.1 expression to inhibit anthocyanin synthesis in pears.

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• VvMYB6,an R2R3-MYB Transcription Factor,is Involved in Anthocyanin Biosynthesis of Grapevine
• ZHU Ziguo, ZHANG Qingtian, HAN Zhen, LI Bo, LI Guodong, LI Xiujie
• Acta Horticulturae Sinica. 2021, 48(3): 465-476. DOI:10.16420/j.issn.0513-353x.2020-0468
• Abstract ( 748 ) HTML ( 707 ) PDF (2843KB) ( 707 ) 　　　

• Here,we demonstrated that VvMYB6,an R2R3-MYB transcription factor,may function as an activator of anthocyanin biosynthesis in grapevine（Vitis vinifera L.）. The VvMYB6 protein contains a conserved R2R3 domain at its N-terminal and localized to the nucleus. Expression studies in grapevine showed that VvMYB6 were strongly expressed in roots,flowers,and berry development of early stages. Ectopic expression of VvMYB6 in tobacco caused the accumulation of anthocyanins in petals and stamens. Metabolomics analysis showed that VvMYB6 expression also caused a marked accumulation of several phenolic compounds,including delphinidin and cyanidin. Expression analysis revealed that several anthocyanin biosynthesis structural genes,including chalcone synthease（CHS）,chalcone isomerase（CHI）,dihydroflavonol 4-reductase（DFR）,anthocyanidin synthase（ANS）and UDP glucose flavonoid 3-O-glucosyl transferase（UFGT）,were strongly up-regulated in transgenic plants. These findings suggest that VvMYB6 plays a key role in anthocyanin biosynthesis.

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• Efficacy of Low Temperature and Mineral Oil Covering in Prolonging Subculture Interval During Grape Germplasm Preservation in Vitro
• CHENG Xiaohua, XU Zhiwei, WANG Li, SHI Xiaoxin, DU Guoqiang
• Acta Horticulturae Sinica. 2021, 48(3): 477-486. DOI:10.16420/j.issn.0513-353x.2020-0304
• Abstract ( 572 ) HTML ( 286 ) PDF (2420KB) ( 286 ) 　　　

• Fourteen grape cultivars were used as plant materials to reveal the influences of low culture temperature and mineral oil covering on medium of plantlets in vitro. The results showed that the low temperature could significantly prolong the subculture period,but the optimal low temperature varied according to the different cultivars. Plantlets cultured in the low temperature could resume growth well after being transferred to routine temperature culture. When the survival rate of 30%-40% was a concern,the optimal temperature was 9 ℃ for‘Sweet Scarlet’,‘Melissa’,‘Summer Royal'and‘Crimson Seedless’cultivars,and the subculture period could reach more than 850 days,and maximum 1 060 days for certain cultivar;the optimal temperature was 12-15 ℃ for‘Kyoho’,‘Jumeigui’,‘Autumn Royal’,‘Flame Seedless’,‘Summer Black’,‘Princess’,‘Lilit’,‘Cabernet Sauvignon’,‘Manicure Finger'and‘Wink’,and the subculture period could last 350 to 600 days. Prior to the low temperature culture,the plantlets needed to be cultured under routine condition for a period of time（preculture）. The duration depended on the culture temperature and the varieties,and it was usually 7 to 21 days. By inoculating shoots with single bud and without leaf,as well as adding 6-8 cm mineral oil on the top of the medium,the subculture period could be up to 420 days in routine temperature culture condition while the control was 150 days. The plantlets resumed growth after the mineral oil was removed.

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• Dynamic Changes of Auxin and Analysis of Differentially Expressed Genes in Walnut Endocarp During Hardening
• YU Shangqi, ZHANG Rui, GUO Zhongzhong, SONG Yan, FU Jiazhi, WU Pengyu, MA Zhihao
• Acta Horticulturae Sinica. 2021, 48(3): 487-504. DOI:10.16420/j.issn.0513-353x.2020-0438
• Abstract ( 679 ) HTML ( 397 ) PDF (4347KB) ( 397 ) 　　　

• In order to study the hardening of the walnut endocarp,which mainly involves the biological process and the role of auxin in the hardening process,the‘Xinlu’walnut was used as the research material. There is a close relationship between walnut endocarp hardening and distribution of vascular bundles on the walnut endocarp surface by morphological observation and lignin deposition analysis;The hardening of walnut endocarp near the vascular tissue is earlier than that away from the vascular tissue. The content of IAA showed a V-shaped change in the hardening of the endocarp. The average content of IAA was the highest than others during the five stages,16.467 ng·g^-1,which was about 6.8 times of the sum of IBA,ICA and ME-IAA. The analysis of intermediate metabolites of lignin synthesis showed that the content of p-coumaryl alcohol of lignin monomer in the hardening area of the endocarp was 16 times of the unhardening area. The content of sinapyl alcohol in the hardening area of the walnut endocarp was extremely high,but it was not detected in the unhardening area,and the content of these two substances in the hardening area of the walnut endocarp showed an overall upward trend with the hardening process. Through transcriptome and proteome correlation analysis,369 differentially expressed genes related to endocarp hardening were obtained. The correlation result of genes that are differentially expressed at both the transcription and protein levels is good,with the lowest correlation coefficient of 0.48124,but the correlation result of all differentially expressed genes is poor,with the highest correlation coefficient of 0.22112. Using Metascape to construct a network of relationships among the top 20 biological functions that are significantly enriched by differentially expressed genes,it is found that four biological processes,namely Phenylpropanoid metabolic process,Response to oxidative stress,Cell wall organization or biogenesis,Amino sugar and nucleotide sugar metabolism were mainly involved in endocarp hardening mainly involve. The fluorescence quantitative results showed that the expression changes trend of AUX/IAA genes JrIAA9,JrIAA16 and JrIAA27 were basically consistent with that of IAA content. It is speculated that IAA plays an important regulatory role in the process of walnut endocarp hardening,and it is of great significance to carry out the research on the mechanism of Bared-nut later.

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• Expression Characteristic Analysis of the BcPG17,a Gene Related to Inflorescence Stem Development of Brassica campestris
• LÜ Meiling, CAO Jiashu
• Acta Horticulturae Sinica. 2021, 48(3): 505-517. DOI:10.16420/j.issn.0513-353x.2020-0520
• Abstract ( 583 ) HTML ( 387 ) PDF (4351KB) ( 387 ) 　　　

• In the present study,a PG gene BcPG17 and its promoter were cloned from Brassica campestris L. ssp. chinensis Makino‘Aijiaohuang’inbred-line Bcajh97-01. Gene expression and promoter activity were explored by qRT-PCR,in situ hybridization and transient transformation of promoter-GUS fusion. The genomic DNA fragment of BcPG17 was 2 015 bp in length,containing nine exons and eight introns. The ORF of BcPG17 was 1 344 bp in length,encoding 447 amino acids. The predicted molecular weight and the theoretical pI of BcPG17 were 48.61 kD and 8.39,respectively. The protein contained a transmembrane domain with a signal peptide sequence at the N-terminus,indicating that the protein may be associated with the cell membrane. Analysis of the amino acid sequence indicated the presence of four typical domains of PG protein,closely relating to other species of Brassica. The highest expression level of BcPG17 was found in the inflorescence stem during flowering,then to a less level in the tetrad stage and uninucleate microspore stage of pollen development. The results of in situ hybridization showed that BcPG17 had a strong signal in all tissues of inflorescence stems during flowering. The 1 442 bp promoter contained at least one cis-acting element related to meristem expression, multiple motifs or elements related to plant hormone response,and four anther-specific motifs,as well as two tapetum-degeneration- retardation（TDR）binding sites. Moreover,transient expression of the promoter-GUS showed strong signal in the second internode and node of the inflorescence stem during flowering,and there was also a significant GUS signal in the anthers in the middle development stage of flower. The above results illustrated that the BcPG17 may regulate the elongation of the inflorescence stem by interacting with other proteins,presumably related to plant hormone metabolism,and it may be involved in the development of the pollen wall by the regulation of TDR protein.

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• Characteristics of the Transcription Factor BrWRKY57 and Its Regulation on BrPPH1 and BrNCED3
• ZENG Zexiang, XIAO Xianmei, TAN Xiaoli, FAN Zhongqi, CHEN Jianye
• Acta Horticulturae Sinica. 2021, 48(3): 518-530. DOI:10.16420/j.issn.0513-353x.2020-0432
• Abstract ( 340 ) HTML ( 231 ) PDF (3724KB) ( 231 ) 　　　

• In this study,a WRKY transcription factor termed BrWRKY57,was obtained from Chinese flowering cabbage. Amino acid sequence alignment and phylogenetic analysis revealed that BrWRKY57 contained one WRKY conserved domain,exhibited the highest homology with Arabidopsis thalianaAtWRKY57,and belonged to sub-group IIc. Real-time quantitative PCR analysis demonstrated that BrWRKY57 was up-regulated during leaf senescence of Chinese flowering cabbage,and its expression was significantly enhanced by abscisic acid（ABA）treatment. Subcellular localization and transcriptional activity analysis suggested that BrWRKY57 was a nuclear protein and had transcriptional activation activity. Moreover,dual-luciferase transient expression assay revealed that BrWRKY57 could activate the promoter activities of chlorophyll catabolic gene BrPPH1and ABA biosynthetic gene BrNCED3. These results indicate that BrWRKY57 might be associated with Chinese flowering cabbage leaf senescence via effecting the genes expression of chlorophyll degradation and ABA synthesis.

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• The Effect of Stu-miR156 Silencing by STTM Technology on Potato Lateral Root Development
• LUO Hongyu, YANG Jiangwei, FENG Ya, ZHANG Huanhuan, LIU Shengyan, ZHANG Ning, SI Huaijun
• Acta Horticulturae Sinica. 2021, 48(3): 531-538. DOI:10.16420/j.issn.0513-353x.2020-0230
• Abstract ( 478 ) HTML ( 365 ) PDF (1613KB) ( 365 ) 　　　

• To elucidate the biological function of Stu-miR156 in potato lateral root development,plantlets in vitro of potato cultivar‘Desiree’were used as dornors. Using STTM（Short tandem target mimic,STTM）technology,the Stu-miR156 silencing expression vector was successfully constructed and further the transgenic plants were obtained viaAgrobacterium-mediated method. qRT-PCR was used to determine the differential expression of Stu-miR156 and its target gene StSPL9in the transgenic potato plants. We constructed a pCAM-GFP-StSPL9 fusion protein expression vector and transformed it into tobacco,thereby confirming that StSPL9 was localized in the cytoplasm and nucleus. The result of qRT-PCR showed that the expression levels of Stu-miR156 in roots,stems and leaves were severely inhibited,while the target gene StSPL9 was up-regulated in the transgenic potato lines L1 and L2. The number of lateral roots of the transgenic plants was significantly reduced and the growth is inhibited compared with the wild type plants.

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• Population Structure and Breeding Systems of Rare and Endangered Gymnospermium kiangnanense（Berberidaceae）
• YU Qinlan, LIU Shouzan, XU Renximou, PAN Chenhang, YAN Yiming, WANG Yiying, XIA Guohua
• Acta Horticulturae Sinica. 2021, 48(3): 539-552. DOI:10.16420/j.issn.0513-353x.2020-0474
• Abstract ( 459 ) HTML ( 346 ) PDF (5022KB) ( 346 ) 　　　

• Gymnospermium kiangnanense（P. L. Chiu）,a rare and endangered plant in China,is a kind of early spring flowering plant of Berberidaceae. Field investigation shows that resources of G. kiangnanense is decreasing day by day,which limits its medicinal and horticultural development. In order to reveal the population structure and breeding system characteristics of G. kiangnanense,two natural populations distributed in Chun'an County and Zhuji City,Zhejiang Province were investigated. In this paper,the specific time life table of the population was compiled,the survival curve and survival function were analyzed,and the population dynamics was predicted by using the time series model,and the breeding system characteristics（hybridization index,pollen/ovule ratio,pollen vitality,stigma receptivity and pollinator insects）were used for determination. Our results showed that:(1) Chun'an population was spindle structure with a large proportion of middle age class,while that of Zhuji population was seriously deficient in middle age class;both populations were in decline type,and their survival curves tended to Deevey-Ⅱtype;(2) Flower characteristics ofG. kiangnanense showed generalized pollination type with P/O value of 7 920;main pollinators of G. kiangnanense were Apis cerana and Episyrphus balteatus,etc.;many ways to ensure success of pollination were involved,for example,the pollination efficiency of G. kiangnanense was improved through the short-term high-density concentrated flowering pattern,extensive pollination system and blank niche in early spring. This paper reveals the causes of G. kiangnanensepopulation formation and predicts the future development trend of the population,so as to provide decision-making basis for the protection and restoration of natural population.

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• Genome-wide Association Study of Flower Color Trait in Prunus persicaf.versicolor
• CHEN Li, XUE Liangjiao, LI Shuxian
• Acta Horticulturae Sinica. 2021, 48(3): 553-565. DOI:10.16420/j.issn.0513-353x.2020-0465
• Abstract ( 448 ) HTML ( 348 ) PDF (1694KB) ( 348 ) 　　　

• Purnus persica f.versicolor has high ornamental value with its two-color and variegated flowers in one single plant. Here,57 P. persica f. versicolor trees from three main distribution areas of ornamental peach were genotyped using Simple Sequence Repeat（SSR）markers. Seventeen polymorphic bands were amplified using six polymorphic primer pairs;the average of effective allele numbers was 2.83. Based on genotyping results by SSR markers,the samples were grouped into three genotypes,of which two to three genotypes were obtained from each collection area. The genotypes of different branches from one peach tree were identical. Further,one representative tree of each genotype was used for the genomic resequencing and variant calling. And phylogenetic analysis was then performed in combination with public genomic resequencing dataset. The results showed that individuals of the three peach genotypes were clustered into one clade,although B20 and T3 were closely related to‘Sahongtao’,whereas W5 was relatively independent,indicating the three genotypes ofP. persica f.versicolorwere cultivated from closely related clones with limited genetic variations. Genome-wide association study（GWAS）was further carried out by integrating single nucleotide polymorphism（SNP）information and flower color phenotypes. Five SNPs significantly associated with flower color trait（P < 10 ^-100）were identified and all of them were located on chromosome 7 of peach genome. Three Dicer-like 2（DCL2）genes were identified in genome segments adjacent to correlated SNP loci,suggesting that DCL2-dependent epigenetic modification may play an important role in the formation of variegated flowers in peach.

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• Isolation and Function Analysis of the Promoter of a Thermal Inducible Gene RCA1 in Rhododendron hainanense
• LI Zheng, LIU Bing, ZHOU Hong, WANG Xiuyun, XIA Yiping
• Acta Horticulturae Sinica. 2021, 48(3): 566-576. DOI:10.16420/j.issn.0513-353x.2020-0483
• Abstract ( 681 ) HTML ( 355 ) PDF (2357KB) ( 355 ) 　　　

• In order to analysis the regulatory mechanism and expression profile of RhRCA1,three-year-old cutting seedlings of Rhododendron hainanense were used as the experimental material to isolate the promoter ofRhRCA1. This promoter was then used to drive the Luciferase and GUS reporters in tobacco and Arabidopsis thaliana respectively,to figure out its activity,tissue specificity and thermal inducibility. The results showed that:(1) Remarkable high expression of RhRCA1 was observed in the quantitative experiment after high temperature treatment,which appeared typical thermal inducibility. (2) The promoter of RhRCA1 with a length of 1 624 bp was cloned and the promoter contained multiple cis-elements related to abiotic stress response,light signals and tissue specificity. (3) A plant expression vector was constructed using theRhRCA1 promoter to drive Luciferase report gene,and was transformed into tabacco to analyse transient expression. The results showed that RhRCA1promoter could strongly respond to heat stress. (4) The promoter and GUSfusion expression vector were constructed and transformed intoArabidopsis. Analysis of T₃ generation transgenic Arabidopsis tissues with histochemical staining showed that heat stress had a significant impact on the induction of RhRCA1 promoter expression in green tissues,including cotyledon,mature leaf,young stem,sepal and seedpods. These results indicated that the promoter ofRhRCA1is a heat-inducible and tissue-specific promoter. This promoter is ideal to drive other genes to improve the thermostability of plants under high temperature by genetic engineering,which has promising applications under the tendency of global warming.

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Research Notes

• Cloning and Analysis of MoDXS Gene and Its Promoter in Morinda officinalis
• XIE Dejin, ZHOU Chengcheng, YANG Ke, REN Ke, YANG Deming, CHEN Lingyan, RONG Jundong, ZHENG Yushan
• Acta Horticulturae Sinica. 2021, 48(3): 577-589. DOI:10.16420/j.issn.0513-353x.2020-0334
• Abstract ( 463 ) HTML ( 319 ) PDF (3586KB) ( 319 ) 　　　

• In the root tissue of Morinda officinalis,three full-length cDNA sequences of 1-deoxy-D-xylulose 5-phosphate synthase genes（MoDXS1,MoDXS2-1 and MoDXS2-2）were successfully cloned and their length were 2 676,2 667,and 2 610 bp,respectively. The coding sequence（CDS）of the three cDNAs were 2 154,2 121,and 2 190 bp,encoding 717,706,and 729 amino acid residues,respectively. Sequence comparison by BlastP in NCBI database revealed that MoDXS proteins had high homology with DXS proteins from other species. The result of the phylogenetic tree displayed that MoDXS proteins had the closest relationship with DXS proteins from Coffea canephora and Coffea arabica. Furthermore,MoDXS1,MoDXS2-1,and MoDXS2-2 proteins were grouped into clade 1,clade 3, and clade 2,respectively. MoDXS1 gene had the highest expression level in roots. The expression level of MoDXS2-1 gene had significant differences in three tissues,and the expression level was the highest in leaves. However,the expression level of MoDXS2-2 gene was the highest in roots but lower in stems and leaves. The plantCARE analysis indicated that the upstream regulation sequences of MoDXS1,MoDXS2-1,and MoDXS2-2 were 2 538,732,and 1 744 bp,respectively. The subcellular localization exhibited that the three MoDXS proteins were located on chloroplast.

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New Technology and New Mathod

• The Rapid Detection of Xanthomonas citri ssp. citri（Xcc）Based on Recombinase Polymerase Amplification（RPA）Assay
• MA Zhimin, DUAN Yu, XU Jianjian, BIN Yu, ZHOU Changyong, SONG Zhen
• Acta Horticulturae Sinica. 2021, 48(3): 590-599. DOI:10.16420/j.issn.0513-353x.2020-0545
• Abstract ( 405 ) HTML ( 288 ) PDF (2191KB) ( 288 ) 　　　

• A detection assay based on recombinase polymerase amplification（RPA）for Xanthomonas citri ssp.citri（Xcc）was established by designing specific primers and optimizing concentration of primers,reaction temperature and reaction time. The method requires no complex equipment such as PCR apparatus,and can complete the detection process at 39 ℃ in 30 min,which is quick and simple. The detection method has strong specificity to Xcc with no cross reaction with other citrus pathogens. The RPA detection sensitivity was 100 times higher than that of ordinary PCR,which was the same as that of real-time quantitative PCR. In 71 citrus samples,22 samples were positive to canker detected by RPA,which was consistent with the results of PCR and real-time quantitative PCR.

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• Development and Application of an Efficient Method for the Amylose/ Amylopectin Ratio Determination in Potato Tubers
• SONG Yuhao, SHI Weiling, ZHANG Jiao, DING Zhenyu, PENG Hongxian, JIANG Chunyan, MA Qiuqin, LI Zhijing, ZHAO Yong, TANG Daobin, ZHANG Kai, WANG Jichun, LIU Xun
• Acta Horticulturae Sinica. 2021, 48(3): 600-608. DOI:10.16420/j.issn.0513-353x.2020-0446
• Abstract ( 472 ) HTML ( 301 ) PDF (761KB) ( 301 ) 　　　

• Potato starch composition（amylose/amylopectin,AM/AP）influences functional characteristics for food and other industrial applications. The determination of AM/AP ratio is of great significance for rational utilization of starch and breeding special varieties with specific starch components. The dual-wavelength method for determination of AM and AP contents was established in a 96-well plate format firstly. It was identified that the AM contents was dramatically overestimated when the AM/AP ratio of tested samples exceeded the AM/AP ratio（33.3%）of the standard curve. Furthermore,the new standard curve of potato AM/AP ratio and wavelength under the maximum absorption peak were established:y= 601.88x^0.0215,R²= 0.9999. This method further improves the accuracy and is applicable over large ranges of AM/AP ratio needed for screening. This method was used to determine the AM/AP ratio from 198 potato varieties（lines）and a few transgenic tubers with high amylose contents. The result revealed that the range of AM contents in our potato genetic resources is 17.4%-33.3%. In conclusion,a simple and efficient method for the accurate estimation of the potato starch composition was established which is especially suitable for the detection of genetic breeding materials and improvement starch composition lines.

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New Cultivars

• A New Late Ripening Apple Cultivar‘Ruixianghong’
• YANG Yazhou, ZHAO Zhengyang, GAO Hua, WANG Leicun, LIU Zhenzhong, WU Yueni, YANG Huijuan, SUN Lulong
• Acta Horticulturae Sinica. 2021, 48(3): 609-610. DOI:10.16420/j.issn.0513-353x.2020-0810
• Abstract ( 1172 ) HTML ( 393 ) PDF (985KB) ( 393 ) 　　　

• ‘Ruixianghong’is a new late ripening red apple cultivar selected from the cross of ‘Qinfu 1’בCripps Pink’. It produces attractive long-cylindrical fruit with a fruit shape index of 0.97. The average fruit weight is 197.3 g. The fruit presents a bright and clean red surface,and it is easy to color,with the capacity of non-bagging cultivation. The flesh is fine-crisp,sweet-sour,and aromatic,containing 16.3% of the soluble solids content,0.29% of the titratable acid content,55.3 mg·kg^-1 of vitamin C content. The fruit hardness is 8.24 kg·cm^-2with a long storage life and high commodity rate. The yield is 45 000-60 000 kg·hm^-2.

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• An Early Maturing Chinese Jujube Cultivar‘Huangying Lingzao’for Table
• LU Lijuan, ZHOU Junyong, SUN Jun, LIU Mao, ZHU Shufang, SUN Qibao
• Acta Horticulturae Sinica. 2021, 48(3): 611-612. DOI:10.16420/j.issn.0513-353x.2019-0898
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• ‘Huangying Lingzao’is a new early maturing Chinese jujube cultivar derived from the local germplasm‘Huangyingzao’in Anhui Province. It has high quality and high yield,which is suitable for fresh-consuming. The shape of the fruit is circle,with the average weight of 12.3 g,up to 22.6 g. The edible rate is 97%. The flesh is crispy,succulent,sweet and delicate. It matures in early August in Hefei. The fruit developing period is about 75 days. It is suitable for growing in open and protected field.

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