Research Papers

• Activity and Function Analysis of MdRDACO1 Flanking the Retro- transposon Mdsolo-LTR1 Insertion Site in‘Red Delicious’Apple Spur Mutants
• MA Fuli1,*，MU Wenlei1,3,*，ZHOU Junyong1,2，LU Lijuan2，SUN Qibao2，WANG Hai-yan1,3，and SUN Jun1,**
• Acta Horticulturae Sinica. 2020, 47(8): 1429-1437. DOI:10.16420/j.issn.0513-353x.2019-0781
• Abstract ( 415 ) HTML ( 710 ) PDF (5091KB) ( 710 ) 　　　
• In our previous study，a Mdsolo-LTR1 insertion was identified as a spur-specific solo LTR （long terminal repeat）located at position 3 768 578 bp on apple chromosome 4 in‘Red Delicious’apple spur mutants. The 1-aminocyclopropane-1-carboxylate oxidase（ACO1）gene，which encoded the rate-limiting enzyme synthesizing ethylene，was localized at approximately 50 kb downstrem of Mdsolo-LTR1 insertion site in spur mutants. In the present study，activity and function analysis of MdRDACO1 flanking the retrotransposon Mdsolo-LTR1 insertion site was further confirmed. The real-time PCR analysis showed that the expression levels of MdRDACO1 in apical bud（L9–L12）and stem（before shoot half lignification）of‘Red Delicious’were higher than those of in‘Oregon spur Delicious’. The function of MdRDACO1 gene was investigated by Agrobacterium-mediated genetic transformation into Arabidopsis. Overexpression of MdRDACO1 gene significantly increased hypocotyl elongation，plant height and the expression level of AtCPS1 gene in transgenic lines. Our results suggested that spur mutants could partly be attributed to Mdsolo-LTR1 insertion，which represses the expression activity of nearby MdRDACO1 gene，down-regulating the expression activity of MdCPS to synthesize gibberellins in spur mutants.
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• Genome Wide Identification of MRLK Family Genes and Expression Analysis in Response to Aphid Infection in Peach
• FAN Meili，PAN Lei，ZENG Wenfang，LU Zhenhua，CUI Guochao，MENG Junren，JIN Zhe，WANG Zhiqiang，and NIU Liang*
• Acta Horticulturae Sinica. 2020, 47(8): 1438-1450. DOI:10.16420/j.issn.0513-353x.2019-0974
• Abstract ( 313 ) HTML ( 556 ) PDF (2868KB) ( 556 ) 　　　
• Conserved protein motif of malectin-like receptor kinases（Malectin，Malectin-like and Pkinase）were used to blast the MRLKs from peach （Prunus persica） protein database. RNA-sequencing data was used to analyze the expression of MRLKs in five peach cultivars with different aphid resistance genotype after green peach aphid（GPA）feeding at different time points（0，3，6，9，12，24，48 and 72 h）. In this study，we identified 41 members of the MRLK family in the peach genome，and the MRLK genes were distributed unevenly on 8 chromosomes in peach. The amio acid number is 391–1 035，molecular weight is 44.05–115.09 kD，pI is 5.38–9.16 of the MRLK family numbers of peach. The phylogenetic tree showed that MRLK family were divided into 5 subgroups of Arabidopsis，rice and peach. The members of the peach MRLK family were divided into 3 subgroups（Ⅰ，Ⅱ，Ⅲ）. The members within each sub-group were highly conserved according to the analysis of motifs compositions and exon/intron organizations. Subcellular location prediction analysis showed that all the MRLK members were located on cytoplasmic membrane. Additionally，prediction on cis-acting elements indicated that these genes were likely to be involved in multiple responses stimulated by light，phytohormone，abiotic and biotic stress. After GPA infection，no expressions of 19 members were detected in the five experimental materials mentioned above，and another 15 family members were found to be no differentially expression between‘P5868’with any other materials. After aphid infection，PpMRLK2，PpMRLK9，PpMRLK22，PpMRLK23，PpMRLK24，PpMRLK26 and PpMRLK32 were constitutionally highly expressed in Rm4 type variety‘P5868’. Among them，PpMRLK26 showed the most significant up-regulation. Further analysis indicated that 22 MRLK genes were constitutively expressed in‘P5868’，as they were stably expressed at different times after aphid infection. Therefore，PpMRLK26 can be considered as a potential candidate gene for Rm4 type aphid-resistance in peach.
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• Expression Characteristics and Interacting Proteins of the Effector SDE70 from‘Candidatus Liberibacter asiatics’in Infected Citrus
• LONG Junhong，ZHAO Ke，DU Meixia，XIE Zhu，CHEN Shanchun，HE Yongrui，and ZOU Xiuping*
• Acta Horticulturae Sinica. 2020, 47(8): 1451-1462. DOI:10.16420/j.issn.0513-353x.2019-0847
• Abstract ( 377 ) HTML ( 537 ) PDF (2516KB) ( 537 ) 　　　
• Citrus Huanglongbing（HLB）is the most devastating disease of citrus. The main pathogenic species is the Asian species（‘Candidatus Liberibacter asiaticus’，Las）in citrus industry. Las has a complete Sec-dependent secretion system which could secrete effectors to target proteins or genes of host to regulate the plant resistance. In order to explore the pathogenesis of Las effectors and their host target genes，a Sec-dependent effector gene SDE70（CLIBASIA_02470）of Las was cloned from infected Jincheng. Informatics analysis showed that the SDE70 protein has a total length of 132 amino acids，and a putative 20 amino acids signal peptide was detected in the N-terminal. The analysis of E. coli alkaline phosphatase activity showed that the signal peptide was functional in transferring protein to outside cell. Subcellular localization analysis showed that the SDE70：：GFP fusion protein accumulated in the onion cytoplasm and nucleus. Real-time quantitative PCR analysis found that the expression of SDE70 in the symptomatic veins of tolerant Sour Pomelo was significantly lower than that in the asymptomatic veins，on the contrary，its expression in the symptomatic veins of susceptible Jincheng orange was significantly higher than that in the asymptomatic veins. In Jincheng orange，the expression of SDE70 in roots was significantly higher than that in veins，while its expression in young leaves was significantly lower than that in old leaves. The data showed that SDE70 exhibited significant differential expressions in different disease-resistant varieties，different developmental stages of symptoms，and different tissues. Twenty-six citrus proteins that interact with SDE70 were screened out by yeast two-hybrid assay. Gene Ontology rich analysis indicated that 42.3%，34.6% and 65.4% of these proteins were involved in the cellular biosynthetic process，the molecular function of ribonucleotide binding，and located on the cytoplasmic matrix or membrane，respectively. Further yeast two-hybrid experiments showed that three target proteins interacted strongly with SDE70 and they were involved in plant vesicle transport and ubiquitination-like pathway. These results suggested that SDE70 effector regulate plant response to Las infection through manipulating the signal transduction and/or cytoplasmic transport pathways in citrus.
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• Genomic Identification of Jujube AP2/ERF Transcription Factors and Their Expression Pattern During Jujube Witches’ Broom Pathogenesis Process
• LI Jidong*，NI Jing*，YE Xia，CHEN Peng，TAN Bin，ZHANG Mengyang，ZHENG Xianbo，ZHANG Yu，and FENG Jiancan**
• Acta Horticulturae Sinica. 2020, 47(8): 1463-1474. DOI:10.16420/j.issn.0513-353x.2019-0965
• Abstract ( 322 ) HTML ( 488 ) PDF (2214KB) ( 488 ) 　　　
• In this study，a total of 175 and 164 jujube AP2 / ERF transcription factors were obtained from the plant transcription factor database and the NCBI database by bioinformatics methods，respectively. Duplicated sequences were deleted after sequences aligning by DNAMAN. ERF domain were confirmed by SMART software. Finally，145 AP2/ERF transcription factors were identified，of which 116，23，and 5 members were divided into ERF，AP2，RAV subfamily，respectively，including another independent gene. The jujube AP2/ERF transcription factors were featured with amino acid numbers among 111–692，molecular weight among 12 446.87–76 154.10 D，and isoelectric point among 4.31–10.11. 105 jujube AP2/ERF genes were mapped to the 12 jujube chromosomes and the others were not. Jujube witches’ broom（JWB） diseased buds were grafted to healthy 1-year-old seedlings and 4-year-old trees to perform an infection process. The response of AP2/ERF transcription factors to JWB phytoplasma was analyzed according to the transcriptome datas and qRT-PCR. Results showed that the expressing level and number of AP2/ERF were different in 6 sampling stages. The expressing level of 48 AP2/ERF were significantly different in 6 periods. Among them，ZjAP2*9，ZjERF49 and ZjERF91 were the most important AP2/ERF transcription factors in response to the phytoplasma.
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• Effects of Exogenous Sucrose on Bulblet Formation of Lycoris sprengeri in vitro
• Lü Xuesi，ZHANG Dong，MIN Ruihan，LI Shiqi，LI Zheng，REN Ziming*，and XIA Yiping*
• Acta Horticulturae Sinica. 2020, 47(8): 1475-1489. DOI:10.16420/j.issn.0513-353x.2019-0415
• Abstract ( 452 ) HTML ( 465 ) PDF (6887KB) ( 465 ) 　　　
• Lycoris sprengeri was used to study the effects of exogenous sucrose concentrations on bulblet formation in vitro，from morphological，histocytological，physiological，biochemical and molecular levels. The results showed that the presence of exogenous sucrose is a necessary condition for the formation of bulblets in vitro，while sucrose concentration（30 g ? L-1 or 60 g ? L-1）had little effect on the number of bulblets. Acting as both carbon and energy source，exogenous sucrose was a key factor for bulblet formation. When exogenous sucrose was present，sucrose and soluble sugar accumulated before the formation of axillary buds，and the accumulation of starch granules at the base of the scale provided a material basis for bulblet formation here. In addition，the presence of sucrose promoted the accumulation of MeJA in plants and inhibited the abnormal increase in the expression of LsWIP1，LsERS2 and LsEIN2 genes levels，which may mean that sucrose initiated a damage protection mechanism as a signaling molecule and promoted the formation of bulblet.
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• Identification of Differential Metabolic Pathways and Key Regulatory Genes in the Two Flower Bud Differentiation Processes of Magnolia liliiflora
• CHENG Shaoyu，Xuan Lingjuan，DONG Bin，GU Cuihua，SHEN Yamei*，ZHANG Mingru，DAI Mengyi，WANG Zhuowei，ZHANG Yingjia，and LU Danying
• Acta Horticulturae Sinica. 2020, 47(8): 1490-1504. DOI:10.16420/j.issn.0513-353x.2019-0963
• Abstract ( 275 ) HTML ( 438 ) PDF (4001KB) ( 438 ) 　　　
• Magnolia liliiflora‘Hongyuanbao’blooms in spring and summer，transcriptome sequencing and metabolome sequencing were analyzed to explore the differential metabolic pathways and key regulatory genes during second flower bud differentiation processes of‘Hongyuanbao’. 43 257 unigenes and 569 metabolites were identified. Thirty-five floral development genes were involved in the twice flower bud differentiation. Combine transcriptomic with metabolomics analysis，4 074 genes were involved in the middle stage of second flower bud differentiation. Meanwhile，sucrose and 3-cyanoalanine were significantly up-regulated in the second time，and methylmalonic acid was significantly down-regulated（|log2FC| ≥ 2）. The correlation value of the corresponding differential genes was |PCC| > 0.80 and P < 0.05 in four KEEG pathways. The correlation between trehalose and seven differential genes were |PCC| > 0.80 in the sucrose and starch metabolic pathway. CCA analysis showed that comparison between the middle stage of twice flower bud differential process identified three KEGG pathways：ko01200 carbon metabolism，ko00630 glyoxylic acid and dicarboxylic acid metabolism and ko02010ABC transport protein. The expression of genes related to floral development，6 genes（MlCOL9，MlGA9，MlGAI，MlSPL4，MlSPY，MlSVP）were selected from 35 different genes for qRT-PCR verification，which verified the accuracy of transcriptome sequencing results. In summary，this study showed that the secondary flower bud differentiation of‘Hongyuanbao’was produced by the combined influence of photoperiod pathway，vernalization pathway，age pathway and gibberellin pathway and 8 metabolic pathways，and the sucrose and trehalose played important role in it.
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• Genome-wide Identification and Expression Analysis of JmjC Gene Family in Response to Different Photoperiods in Dendrobium
• ZHAO Hua1，ZHANG Shuting1，LIU Pudong1，FU Shuai1，YE Wei2，CHEN Yukun1，LIN Yuling1，XU Han1，and LAI Zhongxiong1,*
• Acta Horticulturae Sinica. 2020, 47(8): 1505-1520. DOI:10.16420/j.issn.0513-353x.2019-0933
• Abstract ( 245 ) HTML ( 454 ) PDF (3712KB) ( 454 ) 　　　
• Bioinformatics methods were used to perform the genome-wide identification of Dendrobium JmjC gene. The expression patterns of DoJMJ in different tissues and their responses to various photoperiods were detected by qRT-PCR. Seventeen JmjC gene family members were identified in the Dendrobium officinale genomic database，and they were divided into five subfamilies（JARID1，JHDM3，JHDM2，JMJD6 and JmjC-only）based on the conserved domains. The number of conservative domains in each subfamily varies；the gene structures analysis showed that the numbers of exons and introns in different subfamilies were different. There were similar exon/intron structures within the same subfamilies. Promoter cis-acting elements analysis revealed that DoJMJ family members contained hormone response elements such as Auxin，ABA，GA，MeJA，SA elements，and environmental signaling response elements including light，drought，low temperature，defense and stress elements，qRT-PCR results showed that the expression of ten members were higher in stem and leaf，a few members showed higher expression levels in root，and all members had lower expression in the fruit of the Dendrobium nobile，which speculated that DoJMJ might play a major role in the developmental processes of stem and leaf. In addition，the family members also exhibited different expression patterns in various photoperiod conditions. Eleven members were highly expressed a 12 h/12 h（light/dark）cycle，and a few members showed higher expression levels in 4 h/20 h，8 h/16 h and 24 h/0 h（L/D）light cycles.
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• Cloning and Expression Analysis of Lb_PPR1 Gene in Different Lycium barbarum Fertility Varieties
• GUAN Cuiping，YANG Yajun，and SHI Jing*
• Acta Horticulturae Sinica. 2020, 47(8): 1521-1529. DOI:10.16420/j.issn.0513-353x.2019-0935
• Abstract ( 212 ) HTML ( 315 ) PDF (3679KB) ( 315 ) 　　　
• The pentatricopeptide repeats（PPR）proteins involve in post-transcriptional modifications and editing of specific single-stranded RNAs in the nucleus and organelles via their localization in various organelles，and they play important roles in series events of plant growth and development. In this study，Lb_PPR1 gene was cloned from the fertile line‘Ningqi 1’and the male-sterile line‘Ningqi 5’. Bioinformatics analysis was used to predict the physico-chemical properties，subcellular localization，conserved domain，protein structure and phylogenetic evolution of Lb_PPR1 encoded protein. The results indicated that Lb_PPR1 gene contained a 1 977 bp open reading frame encoding 658 amino acids in both ‘Ningqi 1’and ‘Ningqi 5’，but there were 20 bp and 14 aa differences between the two cultivars. Lb_PPR1 protein was predicted to have 14 tandem repeats，belonged to PLS family，and its subcellular localization was in cell membrane and cytoplasm. Secondary and tertiary structure predictions showed that Lb_PPR1 protein was dominated by α-helix. Phylogenetic analysis showed that Lb_PPR1 had the closest relationship with PPR in Capsicum annuum and Nicotiana attenuate. Quantitative real-time PCR（qRT-PCR）was performed to determine the expression pattern of Lb_PPR1 gene in different organs and different developmental stages of anther. The results showed that Lb_PPR1 was expressed in different tissues of Lycium barbarum，but highest in the fertile line’s flower buds，its expression in the male-sterile line‘Ningqi 5’were all significantly lower than the fertile line‘Ningqi 1’. The above results indicate that Lb_PPR1 gene maybe related to the development of flower organs in Lycium barbarum.
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Research Notes

• Effect of Soil Textures and Rootstock on Rhizosphere Microorganism and Carbon Source Utilization of Apple Roots
• XU Longxiao，XUN Mi，SONG Jianfei，TIAN Xiaozhi，YIN Fangpeng，HUANG Weinan，ZHANG Weiwei，and YANG Hongqiang*
• Acta Horticulturae Sinica. 2020, 47(8): 1530-1540. DOI:10.16420/j.issn.0513-353x.2020-0046
• Abstract ( 300 ) HTML ( 587 ) PDF (947KB) ( 587 ) 　　　
• Bacterial 16S rRNA gene copy number，bacterial rhizosphere effect，microbial community metabolic activity，functional diversity and carbon source utilization types in rhizosphere and non- rhizosphere soils were analyzed in two-year old potted apple trees（Malus × domestica Borkh.‘Red Fuji’ with Malus robusta Rehd. and Malus hupehensis Rehd. as rootstock）planted in sandy loam，loam and clay loam respectively. Results showed that among all parameters that were tested，three of them including the bacterial copy number，microbial community metabolic activity and functional diversity index displayed the exact same trend. Clay loam had the highest numbers followed by loam and sandy loam. Numbers in M. hupehensis were higher than those in M. robusta. Rhizosphere soil had higher numbers than non-rhizosphere soil. Rhizosphere effects in the 2 rootstocks were the largest in sandy loam and the smallest in clay loam，and the bacterial abundance in sandy loam soil was most affected by rootstocks. The utilization capacity of carbon sources of rhizosphere and non-rhizosphere microbial community in clay loam were the highest followed by loam and sandy loam. The utilization capacity of phenolic acids and carboxylic acids in rhizosphere microbial community was significantly higher than that in non-rhizosphere microbial community. Rhizosphere microbial community of M. robusta had the highest utilization capacity of carboxylic acids in sandy loam and the lowest in clay loam whereas M. hupehensis showed the opposite trends. Types of carbon sources used by rhizosphere microbial community varied with soil texture. In sandy loam，amino acids were mainly used，followed by carbohydrates and carboxylic acids; in loam，carbohydrates were mainly used，followed by polymers and amino acids; and in clay loam polymers were mainly used，followed by amino acids and carbohydrates. The principal component analysis showed that the rhizosphere microbial community types of the two rootstocks were separated by different soil texture types and they were gathered in the same soil texture，which indicated that the type of carbon source utilization of apple rhizosphere microbial community was more susceptible to soil texture，while the difference between the two rootstocks had less impacts.
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• Comparative Analysis on Phenolic Compounds Among Different Clones of Vitis vinifera‘Cabernet Franc’
• SHI Hongmei1,2，ZHANG Zhengwen3，WANG Zhe1，HAN Xiaomei1，WANG Yongmei1,2，REN Fengshan1,2,*，and GONG Lei1
• Acta Horticulturae Sinica. 2020, 47(8): 1541-1551. DOI:10.16420/j.issn.0513-353x.2019-0732
• Abstract ( 307 ) HTML ( 463 ) PDF (867KB) ( 463 ) 　　　
• This study is aimed to screen the excellent Vitis vinifera‘Cabernet Franc’clone with higher contents of flavanol and anthocyanin so as to provide a theoretical basis for the breeding of wine grapes in Penglai regions. Cabernet Franc and 3 grapevine clones（214，327，623）in Penglai region were selected as the test samples to determine the contents of the total phenol，total tannin，and total anthocyanidins in grape skin and seeds through spectrophotometer method. In the meantime，contents of phenolic acids，flavonols，flavanols，anthocyanins，and resveratrol were measured by high performance liquid chromatography（HPLC）. The results showed that flavanol was the main type of monomeric phenols and the content of catechin was the highest. The malvidin-3-O-glucoside was the main anthocyanin. Under the same cultivation and management conditions as well as the natural conditions，significant differences were found in phenolic substances among different clones of Cabernet Franc. In addition，obvious differences were observed in the same clones of different cultivation years. Thereinto，the total phenolic content in the skin and seeds，the total tannin，and flavanol in the seed，as well as the phenolic acid and monomer anthocyanin content in the skin and seed were significantly higher in the 623 clone than other grape clones，indicating that the performance of clone 623 was better than that of the clones and Cabernet Franc.
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• Development of SSR Molecular Markers Based on Transcriptome and Analysis of Genetic Relationship of Germplasm Resources in Avocado
• GUO Jun1,2，ZHU Jie1,2，XIE Shangqian1,3，ZHANG Ye1,2，YE Beilei1,2，ZHENG Liyan2，and LING Peng1,3,*
• Acta Horticulturae Sinica. 2020, 47(8): 1552-1564. DOI:10.16420/j.issn.0513-353x.2019-0840
• Abstract ( 385 ) HTML ( 487 ) PDF (1101KB) ( 487 ) 　　　
• The‘Fuerte’（Persea americana Mill.）avocado flowers and small fruits from the avocado germplasm resource nursery of Hainan University were selected for transcriptome sequencing，and 18 010 sequences were obtained，with a total length of 29 422 056 bp. MISA software was used to retrieve the transcriptome sequences data of avocado‘Fuerte’ to obtain 6 312 SSR loci distributed in 4 687 sequences. The frequency of these SSRs was 35.05%. Analysis of SSR locus characteristics showed that the average length of SSRs was 18.90 bp and the average distance between SSRs was 4.66 kb in the unigenes. The major types of SSR repeated motifs were dinucleotide and trinucleotide，which accounted for 87.15% of all the SSRs. AG/CT，AAG/CTT，and AAAT/ATTT were the predominant motifs in dinucleotide，trinucleotide and tetranucleotide groups，respectively. A total of 13 398 primers were designed with Primer 3.0 software for the SSR sequences. Thirty-two avocado germplasm resources were used as experimental subjects to verify the validity of 100 randomly chosen primers，and the genetic relationship of these avocado germplasm was also analyzed. Forty primers showed polymorphism with the He and PIC mean values as 0.529 and 0.456，respectively. A total of 219 bands and 171 polymorphic bands were amplified. On average，each pair of primers produced 4.275 polymorphic fragments. Consistent results were obtanned with the UPGMA clustering and PCA analysis，respectively. When the coefficient was set to 0.74，these avocado germplasms can be divided into 4 groups，which has certain correlation with geographical distribution.
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• QTL Mapping of Six Seed Yield Related Traits in Lotus
• LIU Zhengwei1，GUO Dandan1,2，PENG Jing1，ZHU Honglian1，KUANG Jing1，JI Qun1，WANG Zhixin1，DING Yi3,*，and KE Weidong1,*
• Acta Horticulturae Sinica. 2020, 47(8): 1565-1576. DOI:10.16420/j.issn.0513-353x.2019-0665
• Abstract ( 197 ) HTML ( 339 ) PDF (1614KB) ( 339 ) 　　　
• In this study，a F2 population of lotus including 86 individuals was constructed with the cylindrical type accession‘Middle Lake Wild Lotus’and spherical type‘Chiang Mai Wild Lotus’as female and male parents，respectively. By combining the phenotypic identification of the F2 individuals and the parents in 2017 and 2018 with the genotyping by 197 SSR markers，QTL mapping of six yield-related traits（i.e.，black seed length，black seed width，single seed weight，flower number，carpel number and seed number per seedpod）was carried out. The results showed that all the six yield-related traits were close to continuous normal distribution in the F2 population，which indicated that these traits are quantitative traits controlled by multi genes. In total，twenty-eight QTLs that distributed on seven linkage groups were identified in the two years’ experiments，which explained 5.5%–27.4% of the phenotypic variation with LOD values between 2.55 and 12.34. Twenty-five QTLs（accounting for 89.29% of total QTLs）explained more than 10% phenotypic variation. Four of the twenty-five QTLs [i.e.，black seed length（bsl1），black seed width（bsw6）and flower number fn4.1，fn5）] were repeatedly identified over the two years，explaining 7.33% to 17.6% phenotypic variantion.
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New Technologies and New Methods

• Modification of in vitro Bioassay for Screening Musa Species Against Fusarium oxysporum f. sp. cubense
• WU Yuanli1，HUANG Bingzhi1,*，ZHANG Zhisheng2，and Yang Xingyu1
• Acta Horticulturae Sinica. 2020, 47(8): 1577-1584. DOI:10.16420/j.issn.0513-353x.2020-0214
• Abstract ( 252 ) HTML ( 397 ) PDF (835KB) ( 397 ) 　　　
• It was observed that the final disease severity was mainly affected by sporulation medium，growing time of banana plantlet on medium for interaction system（MIS）before in vitro inoculation，components of MIS medium，and pathogenicity of Fusarium oxysporum f. sp. cubense（Foc）tropical race 4（TR4）strain. The effects of the four factors on final disease severity were studied by using orthogonal experimental design. Logistic regression model analysis of data showed that pathogenicity of Foc TR4 strain was the most important factor（P < 0.001），followed by sporulation medium（P < 0.05），components of MIS medium（P < 0.05），and growing time of banana plantlet on MIS medium before in vitro inoculation. The optimum factor combination for rapid screening was the third-generation rejuvenated strain，potato dextrose water meduim，half-strength Murashige and Skoog salts without organic elements， and 7-day growth of banana plantlet on MIS before in vitro inoculation，which was consistent with the result of verification test.
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Review

• Advances in the Research on Resistance Mechanism of Apple to Ring Rot Disease
• HE Xiaowen，HE Ping，CHANG Yuansheng，WANG Sen，WANG Haibo*，and LI Linguang*
• Acta Horticulturae Sinica. 2020, 47(8): 1585-1594. DOI:10.16420/j.issn.0513-353x.2019-0646
• Abstract ( 282 ) HTML ( 478 ) PDF (779KB) ( 478 ) 　　　
• In China，the pathogen causing apple ring rot disease is Botryosphaeria dothidea. This pathogen penetrates apples through natural orifices and secretes cell degrading enzymes to degrade the apple tissue and promote further infection. Apples can inhibit pathogen infection via the enhancement of cell wall lignification，release of antibacterial compounds，and production of immune proteins. Through a detailed review of the apple ring rot damage and pathogen types，pathogenesis mechanisms，and the resistance mechanisms of apples，this research systematically introduces apple ring rot resistance mechanisms and provides an important theoretical basis for effectively controlling this disease.
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• Molecular Basis and Regulation Strategies for Quality Maintenance of Postharvest Fruit
• XU Xiaodi1,2，LI Boqiang1，QIN Guozheng1，CHEN Tong1，ZHANG Zhanquan1，and TIAN Shiping1,2,*
• Acta Horticulturae Sinica. 2020, 47(8): 1595-1609. DOI:10.16420/j.issn.0513-353x.2020-0284
• Abstract ( 259 ) HTML ( 812 ) PDF (1673KB) ( 812 ) 　　　
• 园艺作物果实采后容易发生品质劣变，造成巨大的经济损失。果实自身衰老和病原菌引起的腐烂是影响果实采后品质劣变的主要诱因。保持果实采后品质和减少腐烂损失不仅对果蔬产业的健康发展至关重要，而且也是为国民健康提供优质安全果品的重要保障。深入认知果实成熟衰老与病原菌致病的分子基础及协同调控机制，对创制果实采后品质维持的精准防控技术具有重要的指导意义。本文中综述了果实采后品质维持的分子基础、调控机制和控制技术方面取得的重要进展。
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• Research Advances of Volatile Terpenoids Metabolism in Citrus
• ZHANG Haipeng1，LIU Cuihua2，LIU Yuan1，WEN Huan1，SHI Yaoqiang3，ZHANG Hongyan1，and XU Juan1,*
• Acta Horticulturae Sinica. 2020, 47(8): 1610-1624. DOI:10.16420/j.issn.0513-353x.2020-0100
• Abstract ( 430 ) HTML ( 909 ) PDF (837KB) ( 909 ) 　　　
• Terpenoids are the most important volatile compounds in citrus fruit，which not only play important roles signal transmission between plant and environment，but also have multiple health benefits for humans. This article reviews the related research on volatile terpenoids in citrus，including the biological functions，specific profiles in different germplasms/tissues，biosynthesis-related genes and citrus taxonomy. The review demonstrates that the current research is limited to compound identification and biosynthetic analysis，and most studies are focused on free volatiles，while fewer reports focused on the bond volatiles，structural genes and regulatory genes，the mechanism of aromatic quality needs to be further dissected. In the future，exploration of the evolution of the metabolism of volatile terpenoids and the function of key genes and transcription factors will be the most important aspects of related research on citrus. In future production，the hotspot of research may be the utilization of citrus germplasms with specific flavors，breeding of new cultivars with the accumulation of specific volatile terpenoids，and improvement of the aromatic quality of certain cultivars.
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New Cultivars

• A New Apple Dwarfing Rootstock Cultivar‘Jizhen 2’
• ZHANG Xueying, LI Zhongyong, SHAO Jianzhu, CHEN Haijiang, and XU Jizhong
• Acta Horticulturae Sinica. 2020, 47(8): 1625-1626. DOI:10.16420/j.issn.0513-353x.2019-0194
• Abstract ( 338 ) HTML ( 304 ) PDF (1252KB) ( 304 ) 　　　
• ‘Jizhen 2’is a new apple dwarfing rootstock cultivar selected from the seedling progenies of‘SH40’. It had a good grafting affinity. Grafted on‘Jizhen 2’as inter-rootstock，the Fuji tree will start flowering in the next year. The flowering and fruiting rate of the 3-year-old tree can reach 90%. The average yield of the 4-year-old tree can reach 15 000 kg ? hm-2. The height of the adult tree is about 85% of the SH40，the branching is 75%–85% of the SH40，and the middle and short branches account for more than 75% of the total branches. The yield can be maintained at 45 000–52 500 kg ? hm-2 in high yield year. The average fruit weight of the Fuji is 256.0 g. The hardness of the Fuji fruit is 8.7 kg ? cm-2. The soluble solids content is 14.5%–16.5%.‘Jizhen 2’is suitable for application in the south-central part of Hebei Province or in similar climate areas.
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• A New Table Grape Cultivar‘Xueyuan Hong’
• LU Renxiang，DONG Sujuan，MENG Xianru，ZHANG Wen，and MA Huiqin*
• Acta Horticulturae Sinica. 2020, 47(8): 1627-1628. DOI:10.16420/j.issn.0513-353x.2019-0909
• Abstract ( 207 ) HTML ( 284 ) PDF (935KB) ( 284 ) 　　　
• ‘Xueyuan Hong’is a new seeded table grape cultivar bred through crossing‘Rousalka’（female parent）and‘Adominique’（male parent），both of which are of vinifera genetic background. The full expanded leaf of the cultivar is very large. The fruit cluster shape is conical，medium in size and high compactness. The berry is very large，with an average weight of 12.9 g，elliptical in shape. The berry skin is red，thin and with astringency in taste. Two seeds per berry on average，and neutral in flavor. The cultivar has good potential for delayed harvest to extend the harvest season and it has high storability. In Beijing area，‘Xueyuan Hong’bud breaks in late March，flowers in mid-May，reaches verasion in mid-to-late July，and ripens in mid-August.
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• A New Extra Early-ripening Citrus Cultivar‘Juxiangzao’
• LI Na1，DENG Ziniu1，LI Dazhi1，ZHANG Yong2，LI Shuju3，PENG Jimiao4，and LONG Guiyou1,*
• Acta Horticulturae Sinica. 2020, 47(8): 1629-1630. DOI:10.16420/j.issn.0513-353x.2019-0295
• Abstract ( 362 ) HTML ( 236 ) PDF (1168KB) ( 236 ) 　　　
• ‘Juxiangzao’，a new extra early-ripening Satsuma Mandarin bud mutation cultivar with strong vigor，oblate fruit and a 0.78–0.80 fruit shape index，orange and smooth peel after fully ripening，strong flavor and good mastication，and 115 g fruit weight，12.2% total soluble solids content，0.55% titratable acid content，385 mg ? L-1 vitamin C，was selected from‘Oita Wase’. The mature period is in the early and middle September，persisting a long harvestable period. In addition，the fruit yield is consistently productive with an average yield of 65 280 kg ? hm-2.
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• A New Melon Cultivar‘Tongnian’
• ZHANG Huimei1，DU Junzhi1,*，HONG Xiaoqiang1，and MA Xinshi2
• Acta Horticulturae Sinica. 2020, 47(8): 1631-1632. DOI:10.16420/j.issn.0513-353x.2019-0234
• Abstract ( 211 ) HTML ( 194 ) PDF (845KB) ( 194 ) 　　　
• ‘Tongnian’melon is developed by crossing 07GA5 as female parent with 07GD10 as male parent. The fruit is oval with golden yellow and smooth surface. The flesh is orange. The central soluble solids content is 16%–18%. The average fruit weight is 1.4 kg. The whole growth period is 90–102 d and the fruit development period is 28–32 d. The cultivar has good resistant to disease and stress. It is suitable for protected-field cultivation in Shaanxi，Hebei，Gansu，Inner Mongolia，etc.
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