Citrus genetic improvement has achieved a great progress during the last six decades in China. A repository harboring more than 1 700 accessions of Rutaceae in Chongqing and an embryogenic callus collection including more than 100 varieties in Wuhan have been established,respectively. Continuing exploration of citrus germplasm resulted in the identification of wild Daoxian tangerine,Honghe papeda and the mini-citrus,a mono-embryonic Hongkong kumquat for functional genmics research. A new type of rootstock,Ziyang Xiangcheng（Citrus junos）has been utilized in Chinese citrus industry. A total of 122 citrus varieties including 121 for scion and one for rootstock have been registered or protected by PVP. Out of the scion varieties,88.5% is from the natural mutation including the bud-sport and chance seedling variation,and the rest from artifically created mutants,such as the irradiation,hybridization and protoplast fusion etc. These varieties covered nearly all types of citrus,including loose-skin mandarin,sweet orange and pummelo etc,with improved seedlessness,mature season and fruit color etc. The omics technologies have been widely used in citrus genetic improvement in China. Genomes including sweet orange and other main citrus species have been sequenced and assembled during the recent decade,as has accelerated cloning of the key genes controlling import agronomic traits,such as the polyembryonic related gene CitRWP etc. Genetic transformation and gene editing are also setup in Citrus. These achievments have laid a solid base for citrus genome-design breeding for the future.

In this study，apple whole-genome data were used to identify and conduct a biological analysis of the MdTOPP gene family. A total of 44 TOPP genes were systematically identified from apple genome，and they distributed on 15 chromosomes. The phylogenetic tree analysis showed that MdTOPP，PpTOPP and AtTOPP were highly homologous；the gene structure and conserved domain analysis showed that 1-2 exons，0-20 introns and 10 conserved motifs were in MdTOPP genes. The promoter cis-acting element analysis showed that the MdTOPP genes were not only affected by the external environment such as light and heat，but also comprehensively regulated by multiple hormones. All the MdTOPP genes have distinctive expression patterns in different apple tissues. MdTOPP13 and MdTOPP28 were identified from the transcriptome data of exogenous cytokinin（6-BA and TDZ）induced apple axillary bud outgrowth，and cloning sequence alignment showed high homology. Using quantitative real-time PCR，the expressions of MdTOPP13 and MdTOPP28 were upregulated after exogenous 6-BA or TDZ applied on the axillary buds of apple rootstock‘SH40’. In summary，MdTOPP13 and MdTOPP28 may play an important role in mediating cytokinin regulation of axillary bud outgrowth.

Flavonoids are a class of secondary metabolites with ‘flavan’ skeleton and thousands of derivatives. The biosynthetic pathways of flavonoids are complicated，and some of them and related enzymes have been analyzed. Flavonoids play important roles in the growth and development of plants and the formation of flowers and fruits. Studies revealed that flavonoids can response to stresses and improve the tolerance and resistance of plants. This article reviews the biosynthetic pathways and molecular regulation mechanism of flavonoids in plants，the response of flavonoid pathways to different stresses，the main roles and mechanisms of flavonoids，and the future research directions. Thus，this article is expected to providing theoretical support for the targeted cultivation of horticultural crop varieties with highly resistant，deep processing，and product development.

This paper introduces the important achievements of pepper breeding over the past 60 years in China. It includes the collection,identification,evaluation,utilization and exploration of germplasm resources. The paper also discusses the important advancement in breeding technologies which includes heterosis utilization,anther culture,marker-assisted selection（MAS）,multiple resistance breeding and shuttle breeding. In addition,the history of pepper breeding is reviewed,including the traditional breeding before 1980s and the modern breeding guided with National scientific and technological research after 1980s. Then,driven by the industrial demands,China's pepper breeding has been undergoing several major optimizations：increasing yield,adjusting growth period,enhancing disease resistance,breeding for easy storage and transportation,breeding processed-food-specific varieties,improving product quality,and breeding for mechanized harvesting. After more than four decades of development,a modern and world-leading commercial pepper breeding system has been completely established. Domestic varieties with independent intellectual property rights are taking over 95% of market share across the country. Meanwhile,there are several unique advantages of in China's pepper breeding industry,such as low barrier to entry,low risk,high efficiency,large team,rich varieties,and high effectiveness. However,there are also several problems that strongly restrict the development of the pepper seed industry in China,including homogenization of pepper varieties,difficulty in expanding pepper seed business enterprises and slow research progress of pepper molecular breeding technology. Long-season varieties cultivated in green house and ornamental pepper varieties are mainly imported because the pepper breeding in China is still lagging behind developed countries. Therefore,the future directions for pepper breeding in China will be improving product quality,producing varieties suitable for mechanized production,breeding varieties with medicinal or other functional ingredients,exploring and advertising local varieties with excellent properties,and innovating novel breeding technologies.

To explore the functions of SAUR（Small Auxin-up RNA）gene family in plant growth and development，bioinformatics methods were used to identify the SAUR genes in peach（Prunus persica）. The chromosome location，gene structure，evolutionary relationship and gene expression were analyzed，and the function of PpSAUR5 was verified through transgenic method. A total of 80 PpSAUR members were identified and divided into 12 subgroups，which were unevenly distributed on the eight chromosomes. The analysis of gene structure showed that 75 PpSAUR genes contained only one exon，and five genes contained two to three exons. Eighteen SAUR genes were found to be associated with tree growth through RNA-seq analysis. These genes exhibited different expression patterns in response to exogenous hormone.Among them，PpSAUR5 was induced by both IAA and GA. PpSAUR5 transgenic Arabidopsis exhibited longer petiole，hypocotyl，root，and less sensitivity to NAA and 2,4-D treatment than wild-type. The results indicated that PpSAUR5 functioned to promote organ elongation.

In this article,the development history of protected horticulture in China during the last 60 years has been reviewed briefly including,the accomplishments of protected horticulture in China in industrial growth,scientific and technical innovation,talents training,and team platform construction. Moreover,the potential for future development and the main tasks of protected horticulture in China are prospected.

The cytokinin response regulator VlRRA1 and its promoter were cloned from‘Kyoho’grape. The expression characteristics of VlRRA1 and the activity of VlRRA1 promoter were analyzed. The results showed that the full-length cDNA of VlRRA1 was 666 bp and encoded 221 amino acids. Conservative domain analysis showed that the gene contained only one phosphoacceptor receiver domain（REC），which belongs to type-A RR genes and can only accept phosphate groups;phylogenetic relationships showed that VlRRA1 was closely related to type-A RR in other species. The yeast self-activation assay illustrates that VlRRA1 has no transcriptional activation activity in agreement with other A-type RR genes and does not have a function similar to that of the B-type RR transcription factor. The results of qRT-PCR showed that VlRRA1 had tissue-specific expression and was mainly expressed in stems，leaves and young fruit，slightly lower expression in inflorescence and ripe fruit，suggesting that VlRRA1 may play an important role in the process of fruit set;exogenous cytokinin forchlorfenuron（CPPU）can promote VlRRA1 expression，while the cytokinin biosynthesis inhibitor lovastatin（LOV）inhibits VlRRA1 transcription. Many elements related to abiotic stress and hormone response were found in VlRRA1 promoter. The results of GUS tissue staining showed that VlRRA1 promoter had promoter activity and could respond to a variety of hormone signals，including three plant hormones related to fruit setting，cytokinin，auxin and gibberellin. These results suggest that VlRRA1 plays an important role in grape fruit setting and young fruit development mediated by cytokinin.

Citric acid is one of the important organic acids in the Horticultural crop fruit. Citric acid significantly affects the taste and flavor of the fruit. This paper reviews the status and function of citric acid synthesis，transport，storage and utilization in the accumulation of fruit. This paper emphasized the influences of the proton transfer of proton pump in the tonoplast and the regulation of citric acid accumulation. In addition，it gives an overview to the status of transcription factors，environmental and climatic factors，cultivation management measures and postharvest treatments in the metabolism and accumulation of citric acid. Based on the comprehensive understanding of the metabolic mechanism of citric acid synthesis and accumulation，the accumulation of citric acid in the fruit can be finely regulated by gene editing，to obtain the fruit with more suitable sugar-to-acid ratio and better taste.

Crassulacean acid metabolism photosynthetic pathway is a kind of carbon concentrating mechanism that evolved from C3 photosynthesis and it is characterized by nocturnal CO₂ fixation and high water use efficiency. Currently，there are growing interests in improving WUE to enhance drought resistance by“transferring”CAM pathway into C₃ crops，also called‘CAM engineering’. CAM engineering has significant application potential in agriculture，while systematical investigations of CAM photosynthetic pathway / plants are a prerequisite to its progression. The wide applications of multi-omics and molecular biology methods have extensively promoted CAM plants related studies. CAM pathway-related key genes and their functions are being gradually revealed，and many CAM plant genomes have been published. Diverse mechanisms are involved in the regulation of the CAM pathway, including transcription factors，hormones，miRNA，lncRNA，alternative splicing，and DNA methylation This article mainly focuses on the latest progress of molecular biology and omics studies on CAM plants. In addtion，future research prospective and study interests are also discussed to guide further investigations on CAM plants.

This review briefly describes the carotenoid metabolic pathway and main flux-controlling steps for carotenoid accumulation in plants. It highlights our recent understanding of the regulatory mechanisms underlying carotenoid accumulation at transcriptional，post-transcriptional，post-translational and epigenetic levels.

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.

In this study，a total of 296 pear germplasms from National Horticulture Germplasm Resources Center Pear Branch Center（Zhengzhou）were collected for fruit spots observation，data collection and photography. During fruit harvesting period，the indicated pear germplasms were sampled and different fruit spot traits，including fruit spots size，fruit spots density，fruit spots height，and the fruit spots area in unit area were comprehensively analyzed. Additionally，sensory evaluation of fruit appearance quality associated with fruit spots in different pear germplasms was performed，and the apperance quality of different pear germplasms was evaluated by grey relation analysis（GRA）and cluster analysis（CA）to establish a comprehensive evaluation model for pear fruit spot traits. The results showed that the relative correlation degree of fruit spots of 296 pear resources ranged from 0.3158 to 0.6526，and the 296 resources were classified into five grades：excellent，good，medium，poor，and extremely poor. Pear varieties including‘Autumn Red’‘Silk Red’‘Red Sensatian’‘Zhongli Meicui’‘Barlett’and‘Dabali’were screened out with excellent fruit spot traits，which have good appearance quality and were consistent with the actual production fruit exterior. On the contrary，pear varieties including‘Puguali’‘Xihuamake’‘Chili’and‘Enli’were screened out with extremely poor fruit spot traits，which have poor appearance quality. Furthermore，the fruit spot traits of 296 pear germplasm resources were divided into five grades by cluster analysis，including excellent，good，medium，poor and extremely poor，which accounted for 7.8%，8.8%，37.1%，34.1% and 12.1% of the tested materials，respectively. Above all，the germplasm resources with excellent fruit spot traits will lay the foundation for the improvement of pear appearance quality，and the germplasm resources with poor fruit traits will be helpful for the investigation of the formation and regulation mechanism underlying pear fruit spots.

In China，there are four kinds of important deciduous fruit trees with a cultivation area of over 666 700 hm²：apple，pear，peach and grape. According to the quality and maturity，several generations of domestic genetic breeders，after decades of collaborative innovation and joint research，created a high-quality and efficient breeding technology system on the basis of excellent germplasm evaluation and creation，and bred a series of high-quality new cultivars of apples and pears with high quality，storability，different maturity and diverse characteristics，and bred high-quality new cultivars of peaches and grapes in early，middle and late maturity. A high-quality and efficient supporting cultivation technology system for new cultivars has been developed，which has promoted the large-scale popularization and application of independent research and development of new cultivars and the high-quality and efficient development of the industry，and provided important support for ensuring the annual demand for high-quality fruits.

Anthocyanin is the main pigment affecting the skin color of apple fruit. In our previous study，MdSLC35F2-like was expressed at higher levels in the‘Nagafu 2’apple red bud mutant than in the wild-type. The open reading frame（ORF）of MdSLC35F2-like was cloned，it is 1 041bp，encoding 346 amino acids，which was predicted to be a hydrophobic α helix transmembrane protein with the highest homology to the PbSLC35F1-like of Pyrus × bretschneideri. Phylogenetic analysis showed that it had the closest evolutionary relationship with P. × bretschneideri，and the furthest evolutionary relationship with Theobroma cacao and Eucalyptus grandis. MdSLC35F2-like sequence and its expression rules before and after the fruit bagging were analyzed. After unbagging，the expression level of MdSLC35F2-like increased firstly，and then decreased with a peak on the third day. The expression level of MdSLC35F2-like in the two kinds of buds was significantly higher than that of‘Nagafu 2’. The above results indicated that the expression level of MdSLC35F2-like gene is positively correlated with anthocyanine content. Meanwhile，its expression levels in different color apple cultivars were compared. The expression of MdSLC35F2-like in red peel cultivars was significantly higher than that in green peel cultivars，and the expression level in red pulp cultivars was higher than that in non-red pulp cultivars. It suggests that MdSLC35F2-like may participate in the anthocyanine accumulation process.

In this review，recent studies on the relationship between fruit sugar accumulation and sugar transporters （mainly includes sucrose transporter SUT related to sucrose accumulation，hexose transporter STP related to hexose accumulation，tonoplast sugar transporter TST that is highly related to vacuolar sugar accumulation，early response to dehydration six like protein ERDL6 related to vacuolar glucose efflux，sugar transporter SWEET newly identified in plants in recent years，and sorbitol transporter SOT，which is unique to Rosaceae plants，etc）in horticultural crops were summarized，and discussed prospects for future research directions on sugar transporters and the molecular biology method for fruit quality improvement.

High-resolution single-cell RNA sequencing（scRNA-seq）technology based on high- throughput sequencing technology has been developed recently to resolve the heterogeneity of plant tissues at the single-cell level,identify distinct cell types in single tissue,and construct continuous cell differentiation trajectories and the transcriptional regulatory networks,in addition,it can search for rare cell types in tissues,thus deeply analyze molecular mechanisms of tissue development. To explore the application of scRNA-seq technology in plants,this paper reviews the progress of scRNA-seq technology and its application in plants. Firstly,the development course of scRNA-seq technology was overviewed; subsequently,we analyzed the progress of scRNA-seq technology in the identification of different plant tissue cell types,screening of specific expression marker genes for different cell types,and analyzing the continuous differentiation trajectories and transcriptional regulatory networks during the development of different plant tissues;finally,we summarized the challenges and future research directions of the

scRNA-seq technology applicating in plants,and aims to provide reference for the application of scRNA-seq technology in more plant species in the future.

VaSTS19 and VdSTS19 were cloned from Vitis amurensis Rupr.‘Tonghua 3’and V. davidii Foex.‘Tangwei’. Sequence analysis showed that the open reading frame of VaSTS19 and VdSTS19 were 1 179 bp，encoding 392 amino acid，and they were located on chromosome 16. The identity between VaSTS19 and VdSTS19 nucleotide and amino acid was 98.81% and 98.21%，respectively. Both VaSTS19 and VdSTS19 are located on the cytomembrane，cytoplasm and nucleus. The expression of STS19 gene and the synthesis and accumulation of resveratrol were significantly promoted when VaSTS19 and VdSTS19 were transferred into tomato by Agrobacterium-mediated method. The promoters of VaSTS19 and VdSTS19 were cloned from‘Tonghua 3’and‘Tangwei’，respectively. cis-Acting elements analysis showed that both promoters contained stress-related elements，hormone-related elements and light-related elements. A sequence alignment showed that the VaSTS19 promoter was demonstrated 60% homology with the VST2 promoter cloned from V. vinifera. The promoters of VaSTS19 and VdSTS19 and their fragments were significantly responsive to SA and MeJA induction in transgenic tobacco leaves. The results indicated that the expression pattern of STS19 and the production of resveratrol may be related to the regulation of the upstream region.

This article focuses on the development and industrial application of vegetable cultivation technologies in China over the past 60 years. The main scientific and technological achievements made in the past 60 years are summarized in terms of facility vegetable production and environmental control technology,soilless cultivation and plant factory technology,seedling nursing and grafting technology,vegetable growth,development and stress tolerance regulation technology,soil maintenance and resource efficient utilization technology,pest and continuous cropping soil sickness prevention and improvement technology,vegetable quality and safety control technology,vegetable mechanized and intelligent production technology. On the basis of the prominent problems analysis of vegetable cultivation in China,the countermeasures and prospect for the future development of vegetable cultivation industry and scientific research in China are also discussed.

In order to explore the effects of abscisic acid（ABA）on monoterpene synthesis in grape berries，this study used table grape species‘Jingxiangyu'with muscat flavor as experimental material，and soaked the clusters with 300 mg · L^-1 ABA twice at one week before and during veraison. The contents of free monoterpenoids at 7，14，21，28 and 35 days after first treatment were analyzed qualitatively and quantitatively by GC-MS. The results showed that 28 kinds of monoterpenes were detected in berries，most of which accumulated during ripening. The total contents of free monoterpenoids in treated berries at maturity was 45.20% higher than that in the control，and the substance that changed most strongly was linalool. To investigate how ABA regulate monoterpenes synthesis，quantitative real-time PCR was used. The results indicated that the expression of ABA synthesis genes（VvNCED1 and VvGT）was much stronger than that of the control. The relative expression of VvβG1 increased after ABA treatment constantly. The transcriptional levels of ABA receptor VvPYL1 and signal transduction related genes VvPP2C2，VvSnRK2.1 and VvABI5 were distinctly higher than the control on 21 and 35 days after treatment respectively. The expression levels of upstream genes about monoterpene synthesis（VvDXS2，VvDXS3，VvDXR，VvGPPS）and monoterpene synthase gene VvPNLinNer was significantly higher. According to the above results，it’s suggested that exogenous ABA enhance ABA signal transduction in berries，which lead to the increase of monoterpene substrate level and facilitate monoterpene synthesis，finally improve the quality of rose flavor grapes.

This review briefly summaries the processes for chrysanthemum development,and recalls the progress and main achievements that have been made in the germplasm resources,inheritance and molecular mechanisms underlying important traits formation,traditional breeding as well as modern biotechnology breeding programs during the last six decades in China. We also summarize the application status of modern biological technologies such as transgenic,genome editing,molecular marker-assisted selection,and multi-omics in the area of chrysanthemum genetics and breeding,and propose suggestions for the development of chrysanthemum genetics and breeding accordingly.