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.

Citrus is usually considered as a typical non-climacteric fruit，with abscisic acid being primarily associated with citrus fruit maturity. However，other hormones，such as ethylene，gibberellin，auxin，also contribute significantly to the maturity and color transition of citrus. In production，a variety of natural hormones and synthetic plant growth regulators are commonly utilized to extend the marketing period of citrus fruits and improve postharvest preservation. This paper provides a comprehensive review of current research advances concerning the role of plant hormones on the maturation of citrus fruits. It delves into the complex relationships between these hormones and investigates the regulatory mechanisms controlled by related transcription factors. The primary aim is to provide reference for further research.

The methods for QTL identification of important traits in fruit trees by genetic linkage map，BSA and GWAS are expounded and compared. The current review summarizes advancement on the identification of QTLs associated with important traits of fruit trees，including external appearance，internal quality，growth and development，resistance to biotic and abiotic stress，in recent years. The purpose of this review is to provide clues for understanding the QTL identification and breeding of fruit tree，and to discuss and propose the methods and strategies that can be used for QTL identification and mapping of important characters in fruit trees.

Sugar is an important factor that determines fruit quality of citrus. Illustrating the characteristic and regulation mechanism of citrus fruit sugar metabolism and transport will greatly contribute to regulating sugar accumulation accurately. In this paper，the mechanisms underlying sugar accumulation were comprehensively reviewed，we also summarized the differences of fruit sugar accumulation in various citrus varieties，the characteristics of sugar accumulation with fruit development and the relationship between sugar and the related enzyme activities. Subsequently，a model of metabolic differences between sucrose accumulation type and hexose accumulation type was mapped in citrus. Moreover，the storage process of sucrose from leaf（source organ）to fruit（sink organ）was described systematically，including phloem loading，unloading，transport and sucrose storage in fruit vacuole. Finally，a model of sugar transport from source to sink was constructed in citrus.

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.

This paper reviews the achievements of Cymbidium germplasm resources，breeding and the molecular research of main ornamental traits. Germplasm resources are the basis for the breeding of Cymbidium. China is the distribution center of this genus with 57 species out of 83 species in the world，and have been formed a large number of traditional varieties which domesticated since 2 500 years ago. To date，the breeding method is still focused on traditional hybridization. There are more than 17 000 Cymbidium hybrids registered on RHS，and 43 new Cymbidium cultivars authorized by the Ministry of Agriculture and Rural Affairs of China. More importantly，Genetic engineering breeding will be the key direction of Cymbidium breeding in the future. A batch of structural genes and transcription factors involved in the main ornamental traits have been unearthed through transcriptome and genome and some of them have been functionally verified，which layed the foundation for the transformation of Cymbidium from traditional breeding to molecular breeding.

Crispy loss is an important reason for reducing the fruit quality of horticultural crops and consumers’ desire to purchase. As a comprehensive concept that includes sound conduction，geometric characteristics and fracture characteristics，the fruit crispy is affected by the cell state，the mechanical strength of the cell wall and the turgor pressure. In-depth understanding of fruit crispy，clarifying crispy evaluation methods and the physiological and biochemical changes in the process of crispy change not only provide a theoretical basis for the production of high-quality fruit，but also provide an important guidance for increasing yield and income. This article summarizes the perceptual process and evaluation of fruit crispy，the factors affecting the crispy and the important progress in related physiological and biochemical metabolism.

Perennial monocots have special underground buds，ground buds，and underground organs. Their dormancy characteristics are obviously different from those of eudicots with aboveground buds. This review article summarized the regulation mechanisms of winter dormancy from environmental，hormonal and carbohydrate in monocots. The regulation mechanisms and research progress of winter dormancy in perennial monocots and eudicots were compared. Combined with the current research progress，suggestions for future directions on the study of winter dormancy regulation in perennial monocots were provided.

Fruit chloroplast quantity and function have a direct impact on fruit quality. Fruit chloroplasts function as assimilation organs before ripening，synthesizing amounts of assimilates for fruit development and quality-related metabolites synthesis，and transform into chromoplasts during ripening，storing nutrients and flavor substances synthesized by different metabolic pathways driven by photosynthesis in the early stage. As a result，increasing fruit quality by controlling chloroplast development has been a research emphasis，and significant progress has been made in the study of fruit chloroplast developmental regulation in tomatos an essential fruit vegetable and model plant. This manuscript reviewed the progress of tomato fruit chloroplast development regulation in terms of transcription factors，light signals，hormone signals，and oxidative stress signals，as well as the challenges and future research directions，to clarify the specific regulation mechanism of fruit chloroplast development and provide new ideas for fruit quality improvement of tomato and other crops.

Orchid senescence caused by the external factors，the metabolic changes of internal organization during the senescence process，and the molecular mechanism of ethylene synthesis and signal transduction pathway regulating orchid senescence were reviewed. The common commercially popular fresh-keeping treatment technologies for cut and potted orchids and their application effects after treatment，and the improvement of orchid senescence-related genes were summarized. Additionally，modern genetic engineering technologies to delay the orchids senescence process and prolong the ornamental time by regulating functional genes were prospected.

This review focused on the recent research findings related to cucumber plant architecture involving genetic pattern，QTL mapping and gene cloning. The molecular were summarized basic research progress in seven aspects：plant height，determinate / indeterminate growth pattern，hypocotyl length，leaf shape，leaf size，lateral branch development ability，and tendril development. The existing related research gaps and shortcomings were analyzed，and a way forward for the development of the ideal plant architecture of cucumber was proposed. The key research directions highlighted in this review will provide a reference for the breeding of the ideal plant architecture of cucumber.

In this paper, the history,the regulation mechanism and key function of the transcription factors CRT/DRE-binding factor (CBF) genes in cold response were reviewed. The relationship between cold tolerant regulated by CBF and ABA was also discussed in this review.

In this study，Camellia sinensis phytoene desaturase gene（CsPDS）and tea caffeine synthase gene（TCS1）as indicator genes and Nicotiana benthamiana as a vector were employed to enrich tobacco rattle virus. The effects of the concentration of infiltration solution，incubation temperature，different vectors and incubation time on the enriched viruses were investigated，with N. benthamiana used as the vector to enrich the viruses. The effects of different inoculation methods and cultivars on the construction of a virus-induced gene silencing（VIGS）system were also investigated in tea plant. The results demonstrated that inoculation of tobacco with acetosyringone（AS）at a concentration of 200 μmol · L^-1 bacteriophage with an optical density（OD₆₀₀）of 1.0 was conducive to virus enrichment in tobacco when incubated at 23 ℃. The leaves of‘Shuchazao’were used to construct the VIGS system of tea plant by injection inoculation, and the system was successfully used to explore the possibility of foreign gene expression with GFP as the indicator gene.

In this study，high temperature experiment was conducted and phylogenetic index were analyzed using Rosa chinensis‘Angela’‘Renyue’and‘Xianjing’as test materials. The results showed that‘Angela’exhibited the highest heat resistance among the three varieties. Comparative transcriptome analysis，co-expression network analysis，protein-protein interaction network analysis and phylogenetic analysis revealed that the improvement of heat tolerance in‘Angela’is associated with the overexpression of heat shock transcription factors（HSFs）and heat shock proteins（HSPs）. Notably，the expression level of HSP gene RcHSP18.1 significantly increased with prolonged heat stress duration. Furthermore，by silencing the homologous gene NtHSP18.1 in tobacco，the heat resistance of tobacco was significantly reduced，confirming the essential role of HSP18.1 in heat stress tolerance. Overexpressing of RcHSP18.1 through gene bombardment and silencing RcHSP18.1 gene by virus induced gene silencing technique have both confirmed the significant role the gene RcHSP18.1 in enhancing heat stress resistance in‘Angela’.

‘Qianquan’is a new Malus crabapple cultivar which has been selected from the seedlings of‘Red Bar’. The cultivar has moderate tree vigor and upright tree appearance. Its one-year-old branches and young leaves are red-brown，while mature leaves are dark green. This cultivar bears deep red buds that open to pink flowers. Its fruit is cylinder with good uniformity，and the background color of fruits is yellow-green which is partially covered by light-red. It is early blooming and the flower formation is easy. It has strong resistance and high adaptability. It is suitable to be planted in apple cultivation areas.

During the past 20 years，the pathway of chlorophyll breakdown has been deep- investigated，especially the structure elucidation of nonfluorescent chlorophyll catabolites which is crucial for the cognizance of chlorophyll breakdown pathway. The effects of some catabolic enzymes involved in the chlorophyll degradation have been further demonstrated and part of the pathway is revised and completed. Moreover，the physiologic roles of chlorophyll catabolites enrich the significance of chlorophyll breakdown which is not only a prerequisite to detoxify the phototoxic pigments catabolites，but also is relevant to the viability of senescent leaves and ripening frui.

The Pepper originated in the semi-arid area in central and southern Bolivia where the annual rainfall is less than 500 mm. This is a subtropical frost-free area. The original wild species are perennial herbs. According to the analysis and study of the starch granules,the Capsicum starch microfossils have been found dating from 8 000-7 500 years ago. Over thousands of years,Capsicum seeds spread out from Bolivia with the help of birds and indigenous peoples,thus spreading throughout South and Central America,then to the southwest of North America. In different ecological regions,more than 10 wild relatives and about 20 wild non-relatives of cultivated species have evolved. Capsicum cultivars evolved from the common ancestor Capsicum chacoense. The purple flower ancestors migrated to the Andes highlands and evolved to Capsicum pubescens. And the white flower ancestors migrated to the relatively dry area of southern Bolivia to evolve to Capsicum baccatum,continuing to migrate to the humid Amazon basin and evolve to the common ancestors of Capsicum annuum,Capsicum frutescens L. and Capsicum chinense Jacquin. They continued to migrate outward,evolving Capsicum annuum in Mexico and northern Central America,Capsicum frutescens L. in the Caribbean,and Capsicum chinense Jacquin in the northern valleys of the Amazon Basin. The pepper domestication started by removing the wild species from the original area for artificial cultivation. The wild species with the fruit small,single-color,upward-facing and easily falling off were domesticated into cultivated species with the fruit succulent,various-shaped,colorful,downward-facing,and not easy falling off,i.e. good economic benefits. Capsicum annuum was the first cultivated species domesticated in Mexico and Central America more than 6 000 years ago,and the other four cultivated species had been cultivated for at least 4 000 years,which are the oldest cultivated plants in America.

Proton pumps are types of important enzymes that promote proton（H⁺）transmembrane transport and cause potential difference between the membrane and participate in a variety of life processes. Organic acids are mainly stored in vacuoles and proton pump promotes proton transmembrane transport accompanied by energy release，which then provides power for the transmembrane transport and storage of organic acids in vacuoles. This paper focuses on the categories，structural characteristics and regulatory factors of proton pumps related to acid transport in horticultural plants，as well as the research status of different types of proton pumps in the regulation of organic acid accumulation，in order to provide reference for the research and regulation of proton pumps and organic acid accumulation in horticultural plants，and then provide a theoretical basis for regulating the quality of horticultural plants.

Peach ( Prunus persica L.‘Bayue Cui’) fruit were dipped in a 5 mmol·L ^{- 1} oxalic acid solution for 10 min and then stored at low temperature for 20 days. Changes in antioxidant ability and polyphenol oxidase ( POD) activity in the fruit were investigated during storage. The results showed that, as compared
with control fruit, higher activities of superoxide dismutase ( SOD) , peroxidaes ( POD) , catalase (CAT) and PPO were observed and lose of ascorbate acid (AsA) was delayed. Moreover, to some extent, active oxygen species (AOS) production including superoxide (O₂· ) and hydrogen peroxide (H₂O₂ ) was inhibited in treated fruit. Itwas suggested that effects of oxalic acid on increases of antioxidant ability and PPO activitymight be beneficial in delaying ripening process and enhancement of disease resistance in peach fruit during storage at low temperature.

Citrus is one of the major sources of dietary flavonoids that are polyphenolic compounds biosynthesized in secondary metabolism pathways. Possibly due to their strong antioxidant activity，flavonoids have many health-promoting properties，including anticancer，antiviral，anti-inflammatory and antimicrobial functions. The types of flavonoids detected in Citrus so far consist of flavanones，flavones，flavonols，dihydrochalcones and anthocyanins. Flavanone glycosides are the most abundant flavonoids in Citrus. Flavonoid composition varied significantly between different Citrus species and between tissue types，i.e. pummelo fruit contains large amounts of the bitter compound neohesperidosides，while sweet orange and mandarin have tasteless rutinosides as their dominant flavonoids. So far，our understanding of flavonoid metabolism is mostly on the structural genes in main biosynthesis pathways，while information on genes regulating the pathways and enzymes involving in glycosylation，acylation and methylation of flavonoid are relatively scarce. Future researches in flavonoid biosynthesis in citrus will reveal more genetic mechanisms controlling the synthesis，modification and distribution of the flavonoids. A better understandingof these mechanisms will provide guidance for citrus breeding programs to produce functional fruit with enhanced levels of flavonoids.