This article presents a new acclimatization method, ex vitro acclimatization in float hydroculture. This protocol ensures the ex vitro acclimatization of the plantlets obtained in vitro in the rooting stage or the ex vitro rooting and acclimatization of the shoots obtained in the multiplication stage. Our hydroculture method is different from the techniques of flotation hydroculture because no fertilizers or plant growth regulators or other biostimulators are used and water oxygenation by bubbling is not provided. Ex vitro rooting and acclimatization in one stage without an in vitro rooting stage in floating cell trays was successfully carried out in Rubus fruticosus and Rosa hybrida cultivars, whereas ex vitro acclimatization of in vitro-rooted plantlets was successfully carried out in Rubus idaeus, Ribes nigrum, Prunus cerasus × P. canescens, Lycium barbarum (Goji berry), Amelanchier canadensis, Drosera rotundifolia, Drosera capillaris, and Nephrolepis sp. In another set of experiments, the floating cell trays were replaced with layers of floating perlite and the latter method was also tested for non-rooted shoots obtained in vitro in the multiplication stage or rooted plantlets obtained in the rooting stage. Direct ex vitro rooting in floating perlite was successful in ‘Tayberry’ (Rubus fruticosus × Rubus idaeus) (78.12% rooting); Amelanchier canadensis, Rubus fruticosus ‘Chester’, Rubus idaeus ‘Erntesegen’, Vaccinium macrocarpon, and Vaccinium corymbosum with rooting percentages above 80%; and Rubus idaeus ‘Willamette’ and Rosa hybrida ‘Cristiana’ with rooting percentages above 80%.

Apple cultivar 'Royal Gala' was multiplied in vitro on starch-gelled MS media supplemented with 0.7 mg/l BAP, which provided intense proliferation of axillary shoots. In order to test the influence of gelling agents upon proliferation rate in this apple cultivar, modified MS media were used, supplemented with 0.7 mg/l BAP and five types gelling agents: fibrous agar, 6.8 g/l; Phytagel + starch, respectively 0.5 + 50 g/l; guar gum, 20 g/l; Psyllium husk, 15 g/l; Phytagel at 2.2 g/l. The highest proliferation rate, 13.44 ± 1.22 was obtained when the media was gelling with the mixture of Phytagel + starch. By using ex vitro rooting and acclimatization in floating perlite, the rooting percentages were between 99.45% and 93.92%, depending on the culture media used in the multiplication stage, from which the axillary shoots were harvested.

The aim of this research was to evaluate the genetic uniformity of blackberry plants (Rubus fruticosus L. ‘Loch Ness’ and ‘Chester Thornless’) obtained by micropropagation. Genetic uniformity was analysed by using RAPD and SRAP markers. For the in vitro multiplication, the slightly modified Murashige and Skoog (1962) basal medium was used, supplemented with 0.5 mg/l 6-Benzyladenine (BA), prepared with tap water and 50 g/l wheat starch as the gelling agent. This culture medium ensured the regeneration of well-developed plantlets, with multiplication rates of more than 42 for both cultivars. The in vitro multiplication was carried out in 30 months including 12 subcultures. The plants obtained from the 3rd and 11th subcultures were compared with the mother plants using 64 SRAP primer combinations (eight forward and eight reverse primers) and 20 RAPD primers to check their genetic fidelity. The amplification products were monomorphic in the micropropagated plants and the mother plant. No polymorphism was detected, thus proving the genetic fidelity and uniformity of the micropropagated plants.

An efficient micropropagation protocol for Rheum rhabarbarum L. was developed in this study. The in vitro rhubarb plants obtained in the multiplication stage (proliferation rate: 5.0 ± 0.5) were rooted in vitro (96% rooting percentage) and acclimatized ex vitro in floating perlite, with 90% acclimatization percentage. To assess the genetic fidelity between the mother plant and in vitro propagated plants, sequence-related amplified polymorphism (SRAP) markers were used. All banding profiles from the micropropagated plants were monomorphic and similar to those of the mother plant indicating 100% similarity. Regarding the polyphenolic profile, gallic, protocatechuic, p-hydroxybenzoic, vanillic, chlorogenic, caffeic, syringic, p-coumaric and ferulic acid were present in different amounts (2.3–2690.3 μg g−1 dry plant), according to the extracted matrix. Aglicons and glycosides of different classes of flavonoids were also identified. The rhizome extracts (both from in vitro and field grown plants) contained resveratrol, a stilbene compound with high antioxidant properties, ranging between 229.4 to 371.7 μg g−1 plant. Our results suggest that in vitro propagation of Rheum rhabarbarum L. represents a reliable alternative to obtain a large number of true-to-type planting material with high bioactive compound content of this valuable nutritional and medicinal species.

Micropropagation of Lycium barbarum cv. 'Ningxia N1' was achieved. The cultures were by initiated by axenical seed germination. The highest shoot proliferation was obtained on the MS media with 1.33 or 2.22 µM benzyl adenine, gelled with wheat starch as an agar alternative. The treatments with 2.22 µM benzyl adenine ensured proliferation rates superior to the ones with 1.33 μM benzyl adenine, but the latter provided longer and more robust shoots. Use of large microcuttings as an explant onto the multiplication media ensured higher in vitro explant survival, higher number of shoots regeneration and more vigorous plantlets. The microcuttings inserted vertically into the media yielded superior growth and multiplication as compared to the microcuttings placed horizontally. The non-rooted, elongated shoots from the treatment 1.33 μM benzyl adenine were either rooted in vitro on a hormone-free MS medium with starch or used for direct ex vitro rooting and acclimatization. The optimal number of microcuttings/vessel for in vitro rooting was 40 and the rooted plantlets were efficiently acclimatized ex vitro by three methods: float hydroculture in floating cell trays, floating perlite, and in Jiffy7 pellets.