Genetic & Breeding·Germplasm Resources·Molecular Biology

• Evaluation of Cold Tolerance of 90 Apple Cultivars and Genome Wide Association Analysis
• KAN Zhiyong, ZHANG Dehui, LI Zhongxing, YU Sisi, QIAN Qian, FAN Tianle, LI Xuewei, MA Fengwang, GUAN Qingmei
• Acta Horticulturae Sinica. 2023, 50(5): 921-932. DOI:10.16420/j.issn.0513-353x.2022-0052
• Abstract ( 1176 ) HTML ( 451 ) PDF (2043KB) ( 451 ) 　　　

• In this study，ninety apple cultivars were used as experimental materials to evaluate cold tolerance by a relative electrical conductivity test. Genome-wide association analysis was conducted on 1 247 162 SNPs detected in apple accessions by genome resequencing technology，and candidate genes significantly associated with cold tolerance were selected. Three cultivars with the strongest cold tolerance were identified，and their relative electrical conductivity was all less than 40%，which were‘Jinhong’，‘Ederbostdorf’and‘Haralson’. Based on the association analysis using 1 247 162 high-quality SNPs and index of relative electrical conductivity characterizing cold tolerance，five significant correlated loci related to cold tolerance were identified，which were distributed on chromosome 4，15，and 16，respectively. Three candidate genes TIF3B1（MD04G1241100），COR47（MD15G1003900），and MD16G1069900 closely related to cold stress tolerance were identified.

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• Construction of cDNA Library of Apple Rootstock‘Qingzhen 1’Leaf and Screen of MdMLO Genes’ Upstream Regulator
• ZHANG Kun, SI Binbin, ZHOU Jun, REN Yufeng, ZHANG Xin, XU Wendi, WANG Jiawei, QIAO Shuai, WANG Huiran
• Acta Horticulturae Sinica. 2023, 50(5): 933-946. DOI:10.16420/j.issn.0513-353x.2022-0159
• Abstract ( 682 ) HTML ( 119 ) PDF (4050KB) ( 119 ) 　　　

• MLO is a plant specific recessive resistance gene family. It is widely believed that it has a negative regulatory effect on powdery mildew. Many powdery mildew resistance MLO genes have been found in both monocotyledon and dicotyledon. However，there are few studies on the mechanism of upstream regulator of MLO genes. In this study，a cDNA library of apple rootstock‘Qingzhen 1’leaf was constructed with a titer of about 4 × 10⁹ cfu · mL^-1，and the recombination rate was 100%. Bioinformatics analysis of apple MLO gene family promoter region showed that there were 38 kinds of cis-acting elements，including hormone，stress defense response as well as growth and development response elements，etc. TCA and TC-rich repeats cis-acting elements were selected as bait sequences and constructed bait vectors named Bait-TCA and Bait-TC for yeast one-hybrid，respectively. The results showed that the Bait-TCA had self-activation and could not be used for screening. Among the Bait-TC obtained 30 sequences，six sequences were involved in plant anti-stress defense response. It suggested that they might be involved in the response of apple to powdery mildew through regulating the expression of MLO genes.

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• Functional Analysis of Transcription Factor CsbHLH3 in Regulating Citric Acid Metabolism of Citrus Fruit
• GUO Jing, LIAO Manyu, JIN Yan, MA Xiaochuan, ZHANG Fen, LU Xiaopeng, DENG Ziniu, SHENG Ling
• Acta Horticulturae Sinica. 2023, 50(5): 947-958. DOI:10.16420/j.issn.0513-353x.2022-0205
• Abstract ( 420 ) HTML ( 209 ) PDF (1977KB) ( 209 ) 　　　

• Transcription factor CsbHLH3 plays an important role in regulating citrate metabolism in citrus fruits，but the specific mechanism remains unclear. In this study，the CsbHLH3 gene was cloned，and transient transformation in tobacco leaves demonstrated the subcellular localization of CsbHLH3 protein in the nucleus. CsbHLH3 overexpression tomato fruit showed a significant increase in the expression of CsbHLH3 while a significant decrease in the content of citrate relative to the wide type. Quantitative analysis revealed that the overexpression of CsbHLH3 induced the up-regulation of SlACO3b and SlPH8. On the contrary，transient suppression of the CsbHLH3 gene in Bingtangcheng leaves resulted in a significantly higher content of citrate than that of the control. In addition，the suppression of CsbHLH3 expression down-regulated the expression of the CsACO2，CsACLα1，CsACLα2 and CsGABP genes in the citrate degradation pathway and proton pump genes CsPH8，CsVHP2 and CsVHP3. Moreover，CsbHLH3 was further confirmed to target the promoter of PH8 and GABP genes to regulate their expression through Y1H and EMSA. These results suggested that the transcription factor CsbHLH3 negatively regulates the citrate level by regulating the expression of several genes related to citrate metabolism，including PH8 and the degradation gene GABP.

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• Molecular Mechanism Study of Exogenous Sorbitol Effects on Sugar Metabolism in Peach Leaves and Fruits
• ZHOU Ping, GUO Rui, YAN Shaobin, JIN Guang
• Acta Horticulturae Sinica. 2023, 50(5): 959-971. DOI:10.16420/j.issn.0513-353x.2022-0190
• Abstract ( 284 ) HTML ( 198 ) PDF (3052KB) ( 198 ) 　　　

• To explore the effects of exogenous sorbitol on leaves and fruits of peach（Prunus persica），the metabolomics and transcriptomics were integrated to investigate changes in sugar（sucrose，glucose，fructose，and sorbitol）contents and expression levels of genes involved in sugar metabolism and transportation as well as relevant metabolic pathways. The results have shown that sucrose，glucose，and fructose contents increased，while there was no difference in sorbitol content in leaves under sorbitol treatment. However，sorbitol content decreased while other sugar contents remained constant in the flesh under sorbitol treatment. Furthermore，content ratios of sucrose/glucose，sucrose/fructose，sorbitol/glucose，sorbitol/fructose，and sorbitol/sucrose were dramatically declined in both leaves and the flesh. Transcriptional patterns of leaves and the flesh under exogenous sorbitol treatment were distinct，in which sugar-related genes including sugar-metabolizing enzymes（PpSDHb，PpPFKa/b/e，PpHXKa，PpSUSb/c and PpINVe）and sugar transporters（PpSOTa/I and PpSWEET10/13），mediated the sucrose，glucose，fructose and sorbitol accumulation in different organs. Transcriptomic analyses confirmed that differentially expressed genes were overrepresented in sugar metabolism-related pathways（including starch and sucrose metabolism in leaves and carbon metabolism in fruits）and other secondary metabolism processes. Our study suggested that exogenous sorbitol influenced soluble sugar contents and sugar composition balance of peach leaves and flesh differently. The leaves- and fruits-specific transcriptional changes of sugar-metabolizing and sugar transporting genes fine-tuned the sugar metabolism.

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• Function Analysis of BcMAX2 in Regulating Axillary Bud Growth in Brassica campestris ssp. chinensis
• XU Lanlan, ZHAO Tianzi, ZHANG Wei, ZONG Chen, HUANG Feiyi, WANG Jianjun, HOU Xilin, LI Ying
• Acta Horticulturae Sinica. 2023, 50(5): 972-984. DOI:10.16420/j.issn.0513-353x.2022-0329
• Abstract ( 306 ) HTML ( 138 ) PDF (3911KB) ( 138 ) 　　　

• MAX2（MORE AXILLARY GROWTH 2）is a gene associated with strigolactone signal transduction. Its function is related to the growth of axillary buds. The effects of MAX2 on the growth of axillary buds were investigated by using Brassica campestris ssp. chinensis the multiple shoot branching cultivar‘Maertou’and common cultivar‘Suzhouqing’. The results showed that there were no differences in the ORF（open reading frame）sequence of BcMAX2 gene obtained from the two materials，but the BcMAX2 promoter sequence of‘Maertou’has a two-base deletion. Subcellular localization analysis indicated BcMAX2 localization in the nucleus. Overexpression of BcMAX2 in Arabidopsis increased BRC1 expression and inhibited axillary bud growth. Silencing of BcMAX2 in‘Maertou’caused the decrease of BcBRC1 expression and promoted the growth of axillary buds. Total of 197 candidate proteins interacting with BcMAX2 were obtained from the cDNA library of Brassica campestris ssp. chinensis. Most of the candidate proteins had binding and catalytic activities，and some of them were involved in signal transduction and stress response of plants. Two interacting proteins were verified by yeast two-hybrid system and bimolecular fluorescence complementation technique. The study showed that BcMAX2 may negatively regulate axillary bud growth by promoting BcBRC1 expression.

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• Creating Pink Fruit and Fruit Without Green Shoulder Using CRISPR/ Cas9 Technology in Tomato
• LI Guobin, CAI Liangyu, XIAO Licheng, WANG Jiafa, ZHANG Dedi, ZHANG Junhong
• Acta Horticulturae Sinica. 2023, 50(5): 985-999. DOI:10.16420/j.issn.0513-353x.2022-0273
• Abstract ( 295 ) HTML ( 162 ) PDF (4326KB) ( 162 ) 　　　

• The key quality-regulating genes SlGLK2 and SlMYB12 were knocked out in tomato cultivars（lines）Ailsa Craig（AC），B5 and B9 using CRISPR/Cas9 binary expression vector system. Nine CRISPR/Cas9 transgenic plants for each of SlGLK2 and SlMYB12 in the AC，three CRISPR/Cas9 transgenic plants of SlGLK2 in the B5，and four CRISPR/Cas9 transgenic plants of SlMYB12 in the B9 were obtained. By sequencing the target sites，it was found that different forms of base deletion，insertion and replacement occurred at 3-4 bp upstream of PAM，mainly 1-10 bp deletion as well as single base G and T insertion. In addition，a large deletions produced between the two targets is 334 bp. Knockout of SlMYB12 in AC showed pink fruits. Knockout of SlGLK2 gene in AC showed the green shoulders of fruits were obviously lighter，and knockout of SlGLK2 gene in B5 showed no‘Green Shoulder’in tomato fruits comparing to the corresponding wild type lines. In this study，SlGLK2 and SlMYB12 gene editing plants were successfully generated in different tomato materials using CRISPR/Cas9 technology，which would provide excellent germplasm for tomato quality breeding.

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Genetic & Breeding·Germplasm Resources·Molecular Biology

• The Characteristics and Chloroplast Ultrastructure of Yellow Leaf Mutant chl234 in Eggplant
• LI Shupei, ZHANG Ying, SHU Jinshuai, CHEN Yuhui, YANG Jinkun, CHEN Lulu, LIU Fuzhong
• Acta Horticulturae Sinica. 2023, 50(5): 1000-1008. DOI:10.16420/j.issn.0513-353x.2022-0300
• Abstract ( 308 ) HTML ( 100 ) PDF (2540KB) ( 100 ) 　　　

• Yellow leaf eggplant mutant chl234 and its wild type were used as materials. chl234 exhibited a yellow-leaf phenotype from cotyledon stage and the true leaves exhibited yellow existed throughout the life cycle. Compared with wild type，chl234 had smaller cotyledon and delayed flowering，and there was no significant difference in the first flower node，plant growth trend，fruit size and seed size between chl234 and wild type. The chlorophyll content in chl234 leaves was significantly lower than that in wild type at the seeding stage，first flowering stage and fourth flowering stage. The net photosynthetic rate，stomatal conductance and transpiration rate of chl234 were significantly lower than that of wild type at the seedling stage，while the intercellular CO₂ concentration was significantly higher than wild type. The net photosynthetic rate，transpiration rate and intercellular CO₂ concentration was no significant difference between chl234 and wild type，while stomatal conductance was significantly lower than that of wild type at fourth flowering stage. chl234 had less grana lamellae stacked pile and irregular arrangement of base grains. The inheritance of the leaf color yellowing trait of chl234 using six genetic analysis populations showed that the leaf color yellowing trait was controlled by a recessive nuclear single gene.

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• The Evolutionary Relationship of Chromosomes in Seven Solanaceae Species
• FU Yu, ZHANG Lingkui, HUANG Yile, YANG Yinqing, CHEN Shumin, ZHANG Kang, LI Liangjun, CHENG Feng
• Acta Horticulturae Sinica. 2023, 50(5): 1009-1024. DOI:10.16420/j.issn.0513-353x.2022-0328
• Abstract ( 363 ) HTML ( 172 ) PDF (4994KB) ( 172 ) 　　　

• In order to trace the evolution of chromosomes of Solanaceae species，a systematic comparative genomic analysis was carried out on seven Solanaceae species. Using the genome of model plant tomato as a reference template，the collinear relationship among seven species of Solanaceae were comprehensively identified，and the genome fragment unit system of Solanaceae was established. Based on this system，the ancestral genome of Solanaceae with 12 chromosomes was reconstructed. The results showed that the ancestral genome gradually formed the current genome structure of Solanaceae mainly through translocation and inversion of genome fragments，and these rearrangement events mostly occurred in the regions of centromere and other repeated sequences were enriched. This study provided an important theoretical reference for further understanding the genome evolution and species differentiation of Solanaceae and other plants.

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Genetic & Breeding·Germplasm Resources·Molecular Biology

• Jasmonic Acid Carboxy Methyltransferase Gene RhJMT Regulates Petal Senescence in Rosa hybrida
• LIU Jiaqi, GONG Feifei, ZHANG Hao, JING Weikun, QU Suping, MA Nan, GAO Junping, SUN Xiaoming
• Acta Horticulturae Sinica. 2023, 50(5): 1025-1036. DOI:10.16420/j.issn.0513-353x.2022-0177
• Abstract ( 276 ) HTML ( 153 ) PDF (3832KB) ( 153 ) 　　　

• In order to understand the mechanism of MeJA in petal senescence，the rose variety ‘Samantha’was used as the test material，and the jasmonic acid carboxyl methyltransferase（JMT）gene RhJMT，a key enzyme in MeJA biosynthesis，was cloned in the petals. Homologous protein sequence alignment and phylogenetic tree analysis showed that RhJMT has a conserved Methylyransf_7 superfamily domain and belongs to the SABATH protein family. The results of real-time quantitative PCR showed that the expression of RhJMT increased significantly after petal senescence. The function of RhJMT was verified by virus-induced gene silencing technology. The results showed that silencing RhJMT significantly delayed petal senescence，and that exogenous application of MeJA could counteract the delaying effect of silencing the RhJMT gene. These results indicate that RhJMT can promote petal senescence and may act by controlling the concentration of MeJA.

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• Analysis of Floral Bud Differentiation and Related Genes Expression Under Different Temperatures in Tulipa gesneriana
• CHEN Xinchen, ZHAO Huimin, WANG Sen, WU Simin, XIANG Lin, CHAN Zhulong, WANG Yanping
• Acta Horticulturae Sinica. 2023, 50(5): 1037-1047. DOI:10.16420/j.issn.0513-353x.2022-0091
• Abstract ( 376 ) HTML ( 183 ) PDF (2813KB) ( 183 ) 　　　

• In this study，the cultivar‘World’s Favourite’was used to compare the processes of floral bud differentiation and floral organ formation under different temperature conditions，as well as a comparison of plant growth and flowering after bulbs planting. The results showed that temperature had a significant effect on the floral buds differentiation and formation of complete flower bud structure. 22 ℃ is the most suitable temperature for floral bud differentiation under which the differentiation speed is the fastest and the floral bud structure is intact. Bulbs under 28 ℃ could form normal floral bud and displayed a faster growth，while the complete floral organ structure failed to be formed under 5 ℃ condition. The expression patterns of genes related to flower development and flowering time regulations were further analyzed by qRT-PCR. The results showed that ABC family genes and flowering time related genes were significantly different in floral buds differentiated under different temperatures. Further cloning and functional exploration of the class A gene TgSQA demonstrated that it encoded 246 amino acids with a typical MADS-box and K-box domain. TgSQA over-expressed transgenic Arabidopsis thaliana obtained an early flowering phenotype compared with the wild type，indicating that TgSQA was a positive regulator during flowering time regulation.

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Genetic & Breeding·Germplasm Resources·Molecular Biology

• Function and Expression Regulation Analysis of Prunus mume PmMYB21 During Filament Elongation
• Yuan Xi, Zhang Man, Ma Kaifeng, Wang Jia, Zhang Qixiang
• Acta Horticulturae Sinica. 2023, 50(5): 1048-1062. DOI:10.16420/j.issn.0513-353x.2022-0119
• Abstract ( 271 ) HTML ( 119 ) PDF (3957KB) ( 119 ) 　　　

• MYB21 is the key transcription factor regulating filament elongation. The flower buds from two Prunus mume cultivars，‘Fenhong Zhusha’（early-flowering）and‘Zaolü’e’（late-flowering），were used as experimental materials. The full length cDNA sequences of PmMYB21 from two cultivars were cloned and found that they have the same sequence. Sequence analysis showed that PmMYB21 protein contains the R2R3 conserved domain of MYB transcription factor. Phylogenetic analysis showed high homology between PmMYB21 and MYB21 protein from other plant species. The subcellular localization experiment showed that PmMYB21 was located in the cell nucleus. The expression level of PmMYB21 in both cultivars increased as the filament elongate during the flower opening process. The up-regulated timing of PmMYB21 expression level in early-flowering cultivar was significantly earlier than in late-flowering cultivar. Additionally，Hypomethylation region of CG-context were detected within-1 529 to-1 243 bp of PmMYB21 promoter region during flowering process in both two cultivars. The methylation level of this region was negatively correlated with the expression level of PmMYB21. The cis-acting elements including elements responsive to abscisic acid，gibberellin，and light were also detected within the hypomethylation region，suggesting that these regulatory processes might be affected by methylation modifications. The results of weighted gene co-expression network analysis（WGCNA）showed that 5 296 DEGs had highest connectivity with PmMYB21，significantly enriched in response to hormone. Combining the candidate genes screened by WGCNA and the expression pattern of candidate genes，PmMYB21 was predicted participated the signal transduction of hormones such as auxin（IAA），gibberellin（GA）and jasmonic acid（JA），and resulting in the filament elongation of P. mume.

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Cultivation Physiology & Biochemistry

• The Rooting Effect and Changes of IAA Content in Constriction，Girdling Treatment During Shoot Layering of Apple Rootstock‘Jizhen 2’
• GAO Meina, SUN Mingfei, ZHU Jie, JING Junli, LI Jia, ZHOU Shasha, LIANG Bowen, XU Jizhong, LI Zhongyong
• Acta Horticulturae Sinica. 2023, 50(5): 1063-1072. DOI:10.16420/j.issn.0513-353x.2022-0155
• Abstract ( 568 ) HTML ( 119 ) PDF (2332KB) ( 119 ) 　　　

• The changes of IAA content and other related indexes during shoot layering in apple dwarfing rootstock‘Jizhen 2’were determined. The results showed that：the rooting rate of constriction treatment was significantly higher than girdling and control，the highest rooting rate was 78.92%；During the shoot layering process，the IAA content of constriction treatment was significantly higher than that of girdling and control，and reached the maximum value of 39.93 ng · g^-1 at 35 days；At adventitious roots induction and formation stage，the activities of POD and PPO of constriction treatment were significantly higher than those of girdling and the control，the IAAO activity of constriction treatment was lower than that of girdling and control；The upregulation of MdPAT1，MdPIN1 during induction in constriction treatment were detected，and reached the highest level at 35 days，which was significantly higher than control；The relative expression of MdYUCCA4 was significantly higher in constriction treatment than that of girdling and control at 25 days and the expression of MdARF17 was relatively low in constriction treatment. In conclusion，The constriction treatment can significantly improve the rooting rate and rooting index of ‘Jizhen 2’rootstock. Auxin IAA plays an important role in inducing and promoting adventitious root elongation of‘Jizhen 2’.

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• The Effect of Rain Shelter Material Coverlys TF150^® on the Fruit Quality of‘Miguang’Grape
• LI Zhonghan, TANG Meiling, ZHENG Qiuling, LIU Minghui, KANG Hui, GAO Zhen, DU Yuanpeng
• Acta Horticulturae Sinica. 2023, 50(5): 1073-1084. DOI:10.16420/j.issn.0513-353x.2022-0057
• Abstract ( 391 ) HTML ( 94 ) PDF (1959KB) ( 94 ) 　　　

• The effect of rain-shelter film polyethylene（PE）fabric Coverlys TF150^® on canopy，fruit microenvironment and fruit quality were investigated by using grape‘Miguang’（Vitis vinifera × V. labrusca）as test material. The experimental results from two consecutive years showed that the light transmittance under CoverlysTF150^® is 11.91% lower than that under polyolefin（PO）film，which reduced the temperature and humidity around the fruit zone and alleviated the stress of high temperature and strong light. CoverlysTF150^® increased fruit size and the content of soluble solids，anthocyanins，total phenols，flavonoids and flavanols，while reduced titratable acid content. In 2020 and 2021，fruit hundred-grain weight increased by 2.15% and 2.46%，fruit soluble solids content increased by 3.70% and 3.04%，fruit titratable acid content decreased by 17.90% and 10.53%，fruit anthocyanin content increased by 18.33% and 11.91%，total phenol content increased by 23.30% and 13.07%，flavonoids content increased by 24.00% and 19.43%，flavanol content increased by 18.20% and 15.58%，respectively. Coverlys TF150^® increased the content of terpenes aromas，especially linalool，while decreased the content of C6 aldehydes such as hexanal aroma.

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• Cultivated Substrates Evaluation for in-situ Observation of Potato Tubers Using Computed Tomography
• TAN Jie, LIU Jiangang, LIU Ju, JIAN Yinqiao, LI Guangcun, JIN Liping, XU Jianfei
• Acta Horticulturae Sinica. 2023, 50(5): 1085-1094. DOI:10.16420/j.issn.0513-353x.2022-0218
• Abstract ( 124 ) HTML ( 79 ) PDF (2669KB) ( 79 ) 　　　

• Soil hinders visualization in tuber growing and developing process，while Computed tomography（CT）technology can avoid destructive sampling and be applied on real-time observation for underground parts of plant. In order to select the cultivation substrate with good CT imaging of potato tubers，CT imaging effect，data extraction and plant growth parameters of six common cultivation substrates with different water content were compared and analyzed. The results showed that potato overground parts in sieved turf grew best，and furthermore，dry weight and fresh weight of tubers in sieved turf or vermiculite & sieved turf were the highest among all substrates. Except for vermiculite，the CT imaging can be improved with water content of substrates decreasing whereas potato plant can not grow normally under serious water shortage. In comparison to other substrates with same water content，there are less background impurities and better CT imaging sieved turf has. Therefore，sieved turf with 20% water content is a suitable cultivation substrate to observe tuber development using CT scanning.

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• Volatility Components of Michelia crassipes Tepals at Different Flowering Stages
• YUAN Jieli, JIN Xiaoling, ZHANG Zheng, XIAO Yujie, YU Qiuxiu, HU Xiaoxuan
• Acta Horticulturae Sinica. 2023, 50(5): 1095-1109. DOI:10.16420/j.issn.0513-353x.2022-0176
• Abstract ( 355 ) HTML ( 104 ) PDF (1922KB) ( 104 ) 　　　

• The volatile components of Michelia crassipes tepals at the flower bud stage，the first-open stage and fully-bloom stage were analyzed using by HS-SPME-GC-Orbitrap-HRMS. A total of 641 volatiles，which could be further classified into 14 groups（mainly terpenes and esters），were identified. Among them，434 volatiles were found in the tepals at the fully-bloom stage，392 volatiles at the first-open stage，and 352 volatiles at the flower bud stage. Also 96，80 and 118 unique volatiles were detected in each stage. At the fully-bloom stage，3 unique alkaloids were detected and they were tetrahydrologanine，tropinone and pilocarpine. The total amount of volatile compounds at fully-open stage was the highest of 668.993 μg · kg^-1，followed by the first-open stage at 628.111 μg ·kg^-1，and the lowest at the bud stage of 522.590 μg · kg^-1. α-guaiene，germacrene B，cis-muurola-4(15), 5-diene，β-caryophyllene，bicyclosesqui- phellandrene，cis-β-ocimene，β-humulene，bicyclogermacrene，γ-muurolene and α-copaene were the major volatiles（content over 13.000 µg · kg^-1）. The analysis of OAV concluded that the characteristic aroma components of M. crassipes tepals included methyl benzoate and α-pinene and the modified aroma components included cis-β-ocimene，β-caryophyllene，linalool and nerolidol. Herbal，floral and woody odor types were the main aroma characteristics. Β-ionone with a low aroma threshold made the tepals in the first-open stage much more floral odor type than that in the bud stage. Benzyl acetate was an unique volatile compound of tepals in fully-open stage，which contributed its strong sweet odor type. The results of principal component analysis indicated that the aroma characteristics of tepals of M. crassipes were not dominated by high-content volatiles，but by the interaction and mutual influence of multiple volatiles. In conclusion，the composition of volatile components in the tepals of M. crassipes is rich，but there are certain differences in different flowering stages. The differences in the types，contents and aroma thresholds of volatile components affected the aroma characteristics of tepals at different flowering stages，making them exhibit diverse fragrance.

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Plant Protection

• The Distribution Pattern of Candidatus Liberibacter asiaticus in Fruit Pith
• LÜ Ruoya, LI Yun, ZHENG Yongqin, DENG Xiaoling, ZHENG Zheng
• Acta Horticulturae Sinica. 2023, 50(5): 1110-1117. DOI:10.16420/j.issn.0513-353x.2022-0200
• Abstract ( 311 ) HTML ( 114 ) PDF (2197KB) ( 114 ) 　　　

• The pathogen of citrus Huanglongbing，Candidatus Liberibacter asiaticus（CLas）was able to multiply in fruit pith. To analyze the proliferation regularity and the distribution pattern of CLas within fruit pith tissue of infected citrus fruit，CLas-infected Wokan（Citrus reticulata Blanco‘Wokan’），Navel orange（C. sinensis），Guanxi pomelo（C. maxima‘Guanxi Miyou’）and Shatian pomelo（C. maxima‘Shatianyou’）were collected for sampling of fruit pith. RT-qPCR was applied to quantify the CLas population in different segments（1.5 cm segment）from the individual fruit pith. The CLas population in different fruit pith from individual fruit of Wokan and Navel orange was also analyzed. The abundance of CLas in different segment of the individual fruit pith and different fruit pith from the individual fruit was statistically compared. Quantitative analyses revealed that CLas population in each of the 1.5 cm segment varied among fruit pith of four citrus varieties. The CLas population in 1.5 cm segments of fruit pith from Wokan and Shatian pomelo fruit was significantly higher than those from Navel orange and Guanxi pomelo fruit. The variable abundance of CLas in four citrus cultivars could be associated with the different substance composition in fruit pith of four citrus cultivars. The reason of CLas tended to multiply in the middle region or stylar region of the individual fruit pith was mainly due to the distribution of nutrients in fruit pith.

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• Screening of Antagonistic Bacterium FX1 Against Erwinia amylovora and Its Control Effect of the Antibacterial Substances on Fire Blight
• HE Xu, HAN Jian, SHENG Qiang, LUO Ming, BAO Huifang, HUANG Wei
• Acta Horticulturae Sinica. 2023, 50(5): 1118-1129. DOI:10.16420/j.issn.0513-353x.2022-0048
• Abstract ( 414 ) HTML ( 69 ) PDF (1355KB) ( 69 ) 　　　

• The antagonistic bacteria against Erwinia amylovorawhich were isolated from plant fermentation were used as the test strains，among which Bacillus velezensis FX1 rescreened out by using perforation-inhibition zone method and co-cultivation method respectively. The results showed that the filtered fermentation broth of FX1 had the strongest antibacterial activity against E. amylovora，and the diameter of inhibition zone was 26.11 mm，after co-culture with the bacteria，the antibacterial rate was 99.99%. The antimicrobial activity of crude extracts from fermentation filtrate of FX1 extracted by different methods were compared. The acid precipitation，ammonium sulphate saturation precipitation and n-butanol extract methods were used for the crude extracts of this strain，and the crude extracts obtained by the acid precipitation and ammonium sulphate saturation precipitation methods exhibited significant antibacterial activity，with the acid precipitation extract showing the strongest antibacterial activity. The biocontrol functional genes were amplified by specific primers，and the gene fragments of bmyB，fenD，ituC，srfAA，srfAB，bioA，yngG，yndJ and TasA were amplified from genomic DNA of the FX1，which showed that the strain may produce lipopetide and antibacterial protein metabolites. The preventive efficacy of spraying FX1 strain lipopeptide crude extract，filtered fermentation broth and fermentation broth in vitro inflorescences of Korla Fragrant Pear for 3-5 d were 79.07%，56.85%，50.02%，respectively. The preventive and therapeutic effects on Pyrus betulaefolia seedlings for 7-15 days were 72.64%，72.85% and 71.54%，61.59%，52.02% and 56.03%，respectively. And the preventive effects was similar to that of agricultural streptomycin（82.33%）. The antibacterial substances of B. velezensis FX1 showed obvious preventive and therapeutic effect on E. amylovora，and has the potential for future in-depth research，development，and application in biocontrol fire blight disease.

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• Identification of Phytopythium helicoides Causing Root Rot of Impatiens hawkeri and Toxicity Test of Different Fungicides in Laboratory
• ZHANG Xiaoyong, LI Shujiang, LONG Qiaofang, YANG Youlian
• Acta Horticulturae Sinica. 2023, 50(5): 1130-1140. DOI:10.16420/j.issn.0513-353x.2022-0128
• Abstract ( 441 ) HTML ( 94 ) PDF (2735KB) ( 94 ) 　　　

• In order to identify the pathogen of Impatiens hawkeri root rot，two pathogenic strains were isolated from diseased roots by tissue separation method. Based on morphological characteristics and ITS and COX II sequences analysis，the pathogen strains were finally identified as Phytopythium helicoides. Inoculating the pathogen on the healthy roots，stems and leaves reproduced the heavy symptoms observed according to the Koch’s rule. The determination of host range showed that P. helicoides could infect not only I. hawkeri，but also I. balsamina，Begonia cucullata，B. elatior，Pelargonium hortorum，Rosa hybrida，R. rugosa，Fuchsia hybrida，Crassula arborescens and Kalanchoe blossfeldiana. In culture tests，the optimum for mycelial growth were at 27-32 ℃ at pH 6-7. Additionally，the toxic effect of ten fungicides against pathogen were evaluated in vitro. Among them 10% oxathiapiprolin OD，98% hymexazol SP，40% dimethomorph WG and 80% mancozeb WP performed good inhibition effects.

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New Technology & New Method

• Method for High Efficiency Isolation of Protoplasts from Pear Leaves and Its Utility for Gene Transient Expression
• GAO Chengyu, WANG Yiheng, JIN Jiangzhou, LI Tao, LI Jindou, ZHOU Mengyao, ZHANG Haixia, MA Hui, ZHANG Yuxing, QI Baoxiu, XU Jianfeng
• Acta Horticulturae Sinica. 2023, 50(5): 1141-1150. DOI:10.16420/j.issn.0513-353x.2022-0264
• Abstract ( 266 ) HTML ( 94 ) PDF (3374KB) ( 94 ) 　　　

• High quality and quantity of protoplasts were succefully isolated from the mesophyll cells of leaves of tissue cultured‘Xinli 7’pear seedlings. This was achieved by optimizing the composition of the cell wall degrading enzymes and the reaction solution where the best results were obtained when the leaves of 30-days old tissue cultured pear seedlings were treated with 1.0% cellulase，0.1% pectinase and 0.4% macerozyme in a buffer containing 20 mmol · L^-1 MES，0.5 mol · L^-1 of D-mannitol，20 mmol · L^-1 of potassium chloride，10 mmol · L^-1 of calcium chloride and 1.0 g · L^-1 of bovine serum albumin（pH 5.7）. Approximately 1.09 × 10⁶ protopl · mL^-1 were recovered with their viability being above 90%. To test their usefulness in genetic transformation in transient expression of proteins 1-2 µg · mL^-1 of pROK2- GFP plasmid DNA was transformed into the prepared protoplasts with 40% PEG-4000. After being cultured for 12 hours GFP was clearly observed in about 40% of the protoplasts，the transformation efficiency reached 40%.

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Review

• Research Progress on Influencing Factors and Mechanisms of Flower Bud Differentiation in Horticultural Plants
• JIN Zhou, LU Shan, JIANG Junhao, LI Shouren, ZHANG Nan, JIANG Xiaoyu, WU Fan
• Acta Horticulturae Sinica. 2023, 50(5): 1151-1164. DOI:10.16420/j.issn.0513-353x.2022-0058
• Abstract ( 902 ) HTML ( 384 ) PDF (816KB) ( 384 ) 　　　

• The differentiation period of flower buds in different horticultural plants is slightly different，and the differentiation time is different. The internal factors affecting flower bud differentiation include endogenous hormones and nutrients. Endogenous hormones mainly include auxin，gibberellin，abscisic acid and cytokinin. Light，temperature，moisture and mineral nutrition can affect the flowering of horticultural plants by regulating hormone levels. Flower bud differentiation mechanism includes the C/N ratio theory，hormone balance hypothesis，hormone signal regulation hypothesis and nutrition hypothesis. At the same time，with the further study of flower bud differentiation in horticultural plants，researchers have found that the process of flower bud differentiation is related to the expression of related genes. This paper reviewed the research progress on flower bud differentiation of horticultural plants in recent years， and looked forward to the main research directions in the future.

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New Cultivars

• A New Red Pear Cultivar‘Hongfengli’
• WANG Jiazhen, LI Juncai, CAI Zhongmin, SHA Shoufeng, LI Hongjun, JIANG Xiaoyan
• Acta Horticulturae Sinica. 2023, 50(5): 1165-1166. DOI:10.16420/j.issn.0513-353x.2020-0362
• Abstract ( 320 ) HTML ( 124 ) PDF (1042KB) ( 124 ) 　　　

• ‘Hongfeng’pear is a new early maturing pear cultivar bred from the cross of‘Red Clapp’בNanguo’. The fruit is suborbicular，and the single fruit weigh is 210 g. The fruit skin is thin and red. The flesh is white，juicy，sour-sweet，with a little aroma and less stone cell after ripening. The soluble solids content is 13.3%，total sugar conternt is 10.84%，titratable acid content is 0.38%，vitamin C content is 0.0229 mg · g^-1. ‘Hongfeng’pear can be cultivated in Anshan，Jinzhou and Huludao in Liaoning Province and other areas with similar climate.

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• A New Processed Okra Cultivar‘Wan Qiukui7’
• YE Sihong, NI Ying, LIU Fei, SUN Hui, WAN Lingzhong, WU Juan, DENG Xiaonan
• Acta Horticulturae Sinica. 2023, 50(5): 1167-1168. DOI:10.16420/j.issn.0513-353x.2022-0059
• Abstract ( 223 ) HTML ( 65 ) PDF (1126KB) ( 65 ) 　　　

• ‘Wan Qiukui 7’is a new cultivar selected by genealogy from the variation single plant of ‘Yan Qiukui 112’. The skin of the fruit is light green，the shape of the fruit is straight，the length of the fresh fruit is about 21 cm，the fruit diameter is 19-22 mm，the average fruit weight is 17.4 g，the number of capsules per plant is 34.1，and the fresh fruit yield is 28 000-34 000 kg · hm^-2. This cultivar has excellent early maturity and can be picked about 60 days after spring sowing. The tender fruit has thick flesh and is suitable for processing okra crisp. It is suitable for planting all over Anhui Province.

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• A New Dendrobium officinale Cultivar‘Taihu 1’
• JIANG Jinlan
• Acta Horticulturae Sinica. 2023, 50(5): 1169-1170. DOI:10.16420/j.issn.0513-353x.2021-0033
• Abstract ( 191 ) HTML ( 85 ) PDF (1087KB) ( 85 ) 　　　

• Dendrobium officinale‘Taihu 1’was a new elite cultivar through artificial hybridization，which was derived from the cross between wild D. officinale 11 and D. officinale 2. The stem is cylindrical and semi-erect，knobby，fleshy，with purple spots. The height is 20-50 cm and the diameter is 0.5 cm. Flowering period is from April to June when cultured in greenhouses in Sanming，Fujian Province. The average annual fresh stem and leaf yield of tissue culture seedlings is 7 500.45 kg · hm^-2 after two years of facility cultivation.

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• A New Arctium lappa Cultivar‘Chuan Dali 1’
• JIANG Yuanyuan, WANG Tao, ZUO Dandan, WANG Long, YANG Ruiwu, LIAO Jinqiu, ZHANG Li
• Acta Horticulturae Sinica. 2023, 50(5): 1171-1172. DOI:10.16420/j.issn.0513-353x.2021-0028
• Abstract ( 260 ) HTML ( 72 ) PDF (1302KB) ( 72 ) 　　　

• ‘Chuan Dali 1’is a new Arctium lappa L. cultivar which is derived from the Arctium lappa L. cultivated mixed population in Sichuan by system selection. The growth period is 290 to 320 d，the flower and fruit period is 100 to 120 d，the number of fruit balls is about 450，and the average production of arctii fructus is 2 321.2 kg · hm^-2. The contents of water，total ash and arctiin in arctii fructus are 5.2%，3.5% and 7.4%，respectively. Field observation showed that it was moderately resistant to black spot disease，powdery mildew，spider mites and aphids. This cultivar has strong regional adaptability and stress resistance，and it’s suitable for cultivation in the eastern foot of the Longquan Mountains in the central of the Sichuan Basin.

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