Abstract
The present study demonstrates the potential of the alginate encapsulation of shoot tips and nodal segments of Gardenia jasminoides Ellis, the short-term cold storage of artificial seeds and subsequent successful conversion to desirable, uniform and genetically stable plantlets. Shoot tips and first-node segments below them, derived from shoots of in vitro cultures, responded better than second-to-fourth-node segments on agar-solidified Murashige and Skoog (MS) nutrient medium and thus, they were used as explants for alginate encapsulation. Explant encapsulation in 2.5% sodium alginate in combination with 50 mM of calcium chloride resulted in the production of soft beads, while hardening in 100 mM of calcium chloride formed firm beads of uniform globular shape, suitable for handling. The addition of liquid MS nutrient medium in the sodium alginate solution doubled the subsequent germination response of the beads. The maintenance of alginate beads under light favored their germination response compared to maintenance in darkness. Encapsulated shoot tip explants of gardenia, which were stored at 4 °C for 4, 8 or 12 weeks, showed a gradual decline in their regeneration response (73.3, 68.9, 53.3%, respectively), whereas, non-encapsulated explants (naked), stored under the same time durations of cold conditions, exhibited a sharp decline in regeneration response up to entirely zeroing (48.9, 11.1, 0.0%, respectively). Shoots, derived from 12-week cold-stored encapsulated explants, were easily rooted in solid MS nutrient medium with the addition of 0.5 μM of Indole-3-acetic acid (IAA) and after transplantation of the rooted plantlets individually to pots containing a peat–perlite (3:1, v/v) substrate, they were successfully acclimatized in the greenhouse under the gradual reduction of 75 or 50% shading with survival rates of 95–100%. The genetic stability of the acclimatized plantlets was assessed and compared with the mother plant using inter simple sequence repeat (ISSR) markers. ISSR analysis confirmed that all regenerated plantlets were genetically identical to the mother plant. This procedure of artificial seed production could be useful for the short-term storage of germplasm and the production of genetically identical and stable plants as an alternative method of micropropagation in Gardenia jasminoides.
Highlights
For the flower industry in Greece, gardenia culture is of great commercial importance with the vast majority of the produced pot plants to be exported to flower markets of the European
The highest number of shoots was counted in the first-node explants, while the longest shoots in the shoot tip explants did not have significant differences compared to the other types of explants (Figure 1B,C)
The findings of the present study proved the feasibility of encapsulating gardenia shoot tips and nodal segments in alginate matrix, successful bead formation and storage at 4 ◦ C for up to 12 weeks and subsequent retrieval at high rates of plantlets of genetic uniformity
Summary
Gardenia jasminoides Ellis, which belongs to the Rubiaceae family, is an evergreen small flowering shrub with dense branches and dark green shiny leaves. Gardenia prefers an acidic soil with a pH of 5.0–6.5 and thrives best in warm temperatures above 5 ◦ C, in humid environments [2]. It is widely used as a garden plant in warm, temperate and subtropical gardens, as well as an ornamental flowering pot plant [3,4]. For the flower industry in Greece, gardenia culture is of great commercial importance with the vast majority of the produced pot plants to be exported to flower markets of the European
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