Horticulture is the science and technology of intensively cultivating plants for food, comfort and beautification purposes. Horticulture comprises a wide range of plants and crops including fruit and nut trees, vegetables, edible fungi, and ornamental plants, as well as tea plants also categorized as horticultural crops in some countries including China. Horticultural products are of great value and serve as important dietary sources of antioxidants, vitamins and mineral nutrients for human nutrition and health. Development of a green and sustainable horticulture, producing more and safer fruit and vegetables, is a prerequisite for meeting the ever-increasing demand of the growing human population.
In contrast to other field crops or model plants, horticulture comprises a diverse group of plants ranging from annual to perennial crops that are primarily grown for fresh consumption, which means their cultivation and breeding methods are quite different from other plants, in particular, in somatic variation or bud-sport, grafting propagation, flowering regulation, organogenetic development and postharvest storage systems. Horticultural research mainly focuses on breeding, cultivation and postharvest production related biological questions, to generate knowledge beneficial for cultivar improvement for better quality and year-round supply, to understand biological basis and regulation of quality formation and maintenance. However, owing to the long juvenile period, polyembryony (such as in citrus), large canopy of perennial horticultural plants, especially for fruit crops, basic and applied research has progressed slowly over the years.
Recently, with the rapid development of high-throughput sequencing technology, research in horticulture has entered the new ‘omics’ era. A large number of datasets for horticultural plants obtained through multi-omics including genomics, epigenomics, transcriptomics, proteomics and metabolomics, are now available, which provides many clues for understanding the molecular basis of agronomically important traits. To date, high-quality draft genome sequences have been accomplished for more than 30 horticultural plant species. Based on these reference genomes, resequencing data and newly developed molecular markers, numerous key candidate loci/genes controlling major agronomical traits of perennial horticultural plants have been identified through BSA and GWAS analysis of genetic populations, using these strategies that have been successfully and widely applied to field crops and model plants. One prime example is the genetic locus responsible for citrus polyembryony, which was recently narrowed to an 80-kb region containing 11 candidate genes by comparative genomic analysis of natural citrus populations, identifying CitRWPas the key candidate gene controlling polyembryony. This approach was also applied to QTL mapping and candidate gene mining for fruit quality (including sugar, acid, TSS and carotenoid), fruit shape, fruit size, fruit weight traits in perennial horticultural plants, such as apple, citrus, grape, peach and pear. Also, recent research on the exploitation and utilization of short-juvenile germplasm, like mini-citrus as a model plant, has facilitated functional genomics of fruit crops. A number of functional genes and their molecular mechanisms were successively identified, thereby accelerating the breeding and genetic improvement of main cultivars.
Considering the rapid progress of horticulture research and its indispensable contribution to human health, Frontiers of Agricultural Science and Engineering (FASE) is launching a special issue “Horticulture Research for Green and Sustainable Development”. We invited experts with rich experience in studies of fruit crops, vegetables, ornamentals and tea plants to share their new research achievements and perspectives. A total of 11 articles are included in this special issue. Its research findings cover QTL mapping and key gene mining for maesil weeping traits (https://doi.org/10.15302/J-FASE-2020379) and tea flavonoid metabolism (https://doi.org/10.15302/J-FASE-2021382), functional identification of apple anthocyanin biosynthetic regulator MdMYB1 in controlling ascorbic acid accumulation (https://doi.org/10.15302/J-FASE-2020367), trifoliate orange PtLEA7 protein (https://doi.org/10.15302/J-FASE-2020368) and apple SUMO E3 Ligase MdSIZ1 (https://doi.org/10.15302/J-FASE-2021388) in modulating drought tolerance, tomato D1 protein turnover in photoprotection under sub-high temperature and high light conditions (https://doi.org/10.15302/J-FASE-2021383), and tomato FNC gene in determining the fruit netted-cracking phenotype (https://doi.org/10.15302/J-FASE-2020374). Electrical signals have been reported to be widely generated in response to various environmental changes and are recognized as vital for plant defense, Hu et al. investigated the characteristics of herbivory/wound-elicited electrical signal transduction in tomato, found GLR3.3 and GLR3.5 function as key regulators in leaflet-to-leaflet electrical signal transduction and JA accumulation (https://doi.org/10.15302/J-FASE-2021395). Ploidy manipulation via diploid by tetraploid interploidy crosses is widely used for breeding triploid seedless cultivars. Xia et al. (https://doi.org/10.15302/J-FASE-2021385) produced 182 triploid and 36 tetraploid plants between the diploid Orah mandarin and three allotetraploid somatic hybrids, and further revealed the mechanism of tetraploid hybrids formation by the fertilization of 2n megagametophytes via second division restitution. Two reviews are also included in this special issue. Ji et al. reviewed the recent advances in the regulation of climacteric fruit ripening in terms of phytohormones, transcription factors and epigenetic modifications (https://doi.org/10.15302/J-FASE-2021386). Makkumrai et al. compared the planting locations, climates, cultivation systems, orchard managements, fruit characteristics, and main metabolites between Chinese and Thailand pummelos, highlighted the potential resources for pummelo breeding and genetic improvement (https://doi.org/10.15302/J-FASE-2021391).
As the guest editors, we thank all the authors and reviewers for their great contributions to this special issue on “Horticulture Research for Green and Sustainable Development”, and the FASE editorial team for their great support. We hope the research findings in this issue represent the main concerns of horticulture researchers and producers, and will be beneficial to quality promotion and cultivar improvement of horticultural crops and ensure a green and sustainable development of horticultural industry.