Orchids are one of the most significant plants that have ecologically adapted to every habitat on earth. Orchids show a high level of variation in their floral morphologies, which makes them popular as ornamental plants in the global market. Floral scent and color are key traits for many floricultural crops. Volatile organic compounds (VOCs) play vital roles in pollinator attraction, defense, and interaction with the environment. Recent progress in omics technology has led to the isolation of genes encoding candidate enzymes responsible for the biosynthesis and regulatory circuits of plant VOCs. Uncovering the biosynthetic pathways and regulatory mechanisms underlying the production of floral scents is necessary not only for a better understanding of the function of relevant genes but also for the generation of new cultivars with desirable traits through molecular breeding approaches. However, little is known about the pathways responsible for floral scents in orchids because of their long life cycle as well as the complex and large genome; only partial terpenoid pathways have been reported in orchids. Here, we review the biosynthesis and regulation of floral volatile compounds in orchids. In particular, we focused on the genes responsible for volatile compounds in various tissues and developmental stages in Cymbidium orchids. We also described the emission of orchid floral volatiles and their function in pollination ecology. Taken together, this review will provide a broad scope for the study of orchid floral scents.

Biotechnological approaches have been used to modify the floral color, size, and fragrance of ornamental plants, as well as to increase disease resistance and vase life. Together with the advancement of whole genome sequencing technologies, new plant breeding techniques have rapidly emerged in recent years. Compared to the early versions of gene editing tools, such as meganucleases (MNs), zinc fingers (ZFNs), and transcription activator-like effector nucleases (TALENs), clustered regularly interspaced short palindromic repeat (CRISPR) is capable of altering a genome more efficiently and with higher accuracy. Most recently, new CRISPR systems, including base editors and prime editors, confer reduced off-target activity with improved DNA specificity and an expanded targeting scope. However, there are still controversial issues worldwide for the recognition of genome-edited plants, including whether genome-edited plants are genetically modified organisms and require a safety evaluation process. In the current review, we briefly summarize the current progress in gene editing systems and also introduce successful/representative cases of the CRISPR system application for the improvement of ornamental plants with desirable traits. Furthermore, potential challenges and future prospects in the use of genome-editing tools for ornamental plants are also discussed.

Light-emitting diodes (LEDs) are currently being used as a light source for in vitro regeneration or the growth of plants in a controlled environment. However, it is crucial to define the target system’s sensitivity to light quality before LEDs may be employed as the exclusive source of light. The objective of the present work was to investigate the influence of red (R), blue (B), white (W), and a combination of red plus blue (1:1) and red, blue, and green (1:1:1) LEDs on Gerbera jamesonii cv. ‘Shy Pink’ during in vitro regeneration. It was observed that LED lighting had a substantial impact on the process of shoot regeneration, shoot growth, and rooting of the shoots. When compared to other light treatments, red plus blue (1:1) LED had the greatest impact on the regeneration of shoots, growth of shoots, and root regeneration from shoot and root growth. Length of shoots, height of plantlets, and petiole length were affected by a red LED, and leaf length, width, and area were affected by a blue LED. The content of photosynthetic pigments (Chl a, Chl b, total chlorophyll, and carotenoids) was higher with acclimatized plants upon transplantation, which were regenerated under blue LEDs. In acclimatized plants, photosynthetic efficiency was calculated. Higher internal CO₂ concentrations (Ci), photosynthetic rates (Pn), stomatal conductance (Gs), and transpiration rates (Tr) were seen in plants that were grown under red plus blue (1:1) LED. However, the plants that were grown under white LEDs had higher chlorophyll fluorescence (Fv/Fm). Collectively, the current results suggest that red and blue LED is suitable for in vitro regeneration of Gerbera jamesonii cv. ‘Shy Pink’ plants compared to red, blue, and white LEDs.

Temporary immersion system (TIS) cultures are reported to be superior when compared to semi-solid (SS) and liquid (LQ) cultures for the in vitro plant regeneration of many plant species. In the present study, we used a TIS for plant regeneration of Gerbera jemesonii “Shy Pink” and compared the results with that of SS and LQ cultures. The number of shoots regenerated in the SS, LQ, and TIS cultures was 6.93, 3.13, and 3.03, respectively. The shoots regenerated with the SS and LQ cultures demonstrated 3.33 and 4.22% hyperhydricity, whereas the shoots regenerated with the TIS were healthy even though the number of shoots regenerated was less. The plantlets regenerated with the TIS demonstrated higher values for the number of roots, root length, biomass of the plantlets, leaf length/width, and area compared to the SS and LQ cultures. When the G. jemesonii “Shy Pink” plants were regenerated using the TIS, their levels of photosynthetic pigments were highest. The number of stomata on the abaxial surface of their leaves was 11.40, and the frequency of closed stomata was 59% for the plants regenerated with the TIS. The number of stomata was 21.4 and 14.5 for the plants regenerated with the SS and LQ cultures, respectively. Meanwhile, the frequency of closed stomata was 13% and 15% for the plants regenerated with SS and LQ cultures. Furthermore, G. jemesonii “Shy Pink” showed the highest survival of plants when regenerated in the TIS compared to SS and LQ cultures. The TIS was found to be the most suitable culture system for plant regeneration of G. jemesonii “Shy Pink” compared to SS and LQ cultures.

Roses (Rosa hybrida) are a highly merchandised flower but lack blue varieties. Overexpression of the flavonoid 3′,5′-hydroxylase (F3′5′H) gene can increase the accumulation of blue pigment (delphinidin anthocyanin). However, sometimes the effect of F3′5′H gene alone is inadequate for producing blue flowers. Furthermore, the internal environment of the cell, such as an increase in pH, can also help the conversion of anthocyanins to blue pigments. Nonetheless, genetic engineering methods can simultaneously introduce multiple genes at the same time to regulate the development of blue pigments to achieve the ultimate breeding goal of producing blue color in roses. In the present study, to simultaneously adjust the accumulation of delphinidin and vacuolar pH, we introduced the Viola tricolor flavonoid 3′,5′-hydroxylase (VtF3′5′H) and Rosa hybrida Na+/H+ exchanger (RhNHX) genes into the white rose line “KR056002” using Agrobacterium-mediated transformation. The quantitative real time polymerase chain reaction (qRT-PCR) results showed that the heterologous genes in the transgenic lines were highly expressed in petals and leaves, and simultaneously promoted the expression of related anthocyanin synthesis structural genes. Obvious color changes were observed in both petals and young leaves, especially when petals changed from white to red-purple. The formation of delphinidin was not detected in the petals of control plants, whereas the petals of transgenic lines had higher delphinidin content (135–214 μg/l) and increased pH value (0.45–0.53) compared with those of control plants.