Tissue Culture in Ornamentals: Cultivation Factors, Propagation Techniques, and Its Application

Abstract

Ornamentals come in a variety of shapes, sizes, and colors to suit a wide range of climates, landscapes, and gardening needs. Compared to demand, a shortage of plant materials and diversity force the search for solutions for their constant acquisition and improvement to increase their commercial value, respectively. In vitro cultures are a suitable solution to meet expectations using callus culture, somatic embryogenesis, protoplast culture, and the organogenesis of protocorm-like bodies; many of these techniques are commercially practiced. Factors such as culture media, explants, carbohydrates, plant growth regulators, and light are associated with the success of in vitro propagation. Techniques, especially embryo rescue and somatic hybridization, are widely used to improve ornamentals. The development of synthetic seed allows season-independent seed production and preservation in the long term. Despite the advantages of propagation and the improvement of ornamentals, many barriers still need to be resolved. In contrast to propagation and crop developmental studies, there is also a high scope for molecular studies, especially epigenetic changes caused by plant tissue culture of ornamentals. In this review, we have accumulated and discussed an overall update on cultivation factors, propagation techniques in ornamental plant tissue culture, in vitro plant improvement techniques, and future perspectives.

Keywords: callus; epigenetic variation; hybridization; in vitro; protocorm-like body; protoplast fusion; somatic embryogenesis; synthetic seeds.

Figure 1

The application of monochromatic white (a), red (b), blue (c), and green (d) LEDs with specific wavelengths (white LED; 420–750 nm, red LED; 580–670 nm, blue LED; 420–550 nm, and green LED; 460–610 nm) for in vitro PLB proliferation.

Figure 2

A detailed scheme of protoplast isolation and establishment of an in vitro protoplast culture.

Figure 3

Diagrammatic presentation of the steps involved in somatic embryogenesis for mass propagation in plants.

Figure 4

Process of embryo rescue from immature (or non-viable) seed after hybridization.

Figure 5

Illustration of somatic hybrid or cybrid development through protoplast fusion. Here, NaNO₃; sodium nitrate, Ca(NO₃)₂; calcium nitrate, PA; polyvinyl alcohol, DS; dextran sulfate, polyethylene glycol (PEG).

Figure 6

Production and application of synthetic seeds. The numbers in the figure represent the ending point of each step, such as the production of synthetic seeds (1), short-term storage of synthetic seeds (2), synthetic seeds for transportation (3), long-term storage of synthetic seeds (4), and plantlet generation from synthetic seeds (5).

Figure 7

In vitro chromosome doubling (ploidy manipulation) for genetic diversification.

Figure 8

Prospects for advanced molecular research in plant tissue culture using orchid plants as an example. Here, Tc; Tissue culture regenerated plants, Vs; traditional vegetatively propagated plants.