Somatic embryogenesis from flower tepals of Hippeastrum aiming regeneration of virus-free plants

Morpho-histology of co-occurrence of somatic embryos, shoots, and inflorescences within a callus of Limonium 'Misty Blue'

This is the first attempt to report the co-occurrence of somatic embryos, shoots, and inflorescences and their sequential development from stem cell niches of an individual callus mass through morpho-histological study of any angiosperm. In the presence of a proper auxin/cytokinin combination, precambial stem cells from the middle layer of a compact callus, which was derived from the thin cell layer of the inflorescence rachis of Limonium, expressed the highest level of totipotency and pluripotency and simultaneously developed somatic embryos, shoots, and inflorescences. This study also proposed the concept of programmed cell death during bipolar somatic embryo and unipolar shoot bud pattern formation. The unique feature of this research was the stepwise histological description of in vitro racemose inflorescence development. Remarkably, during the initiation of inflorescence development, either a unipolar structure with open vascular elements or an independent bipolar structure with closed vascular elements were observed. The protocol predicted the production of 6.6 ± 0.24 and 7.4 ± 0.24 somatic embryos and shoots, respectively, from 400 mg of callus, which again multiplied, rooted, and acclimatised. The plants' ploidy level and genetic fidelity were assessed randomly before acclimatisation by flow cytometry and inter simple sequence repeats (ISSR) marker analysis. Finally, the survivability and flower quality of the regenerated plants were evaluated in the field.

Phytochemical Composition and Biological Activities of Extracts from Early, Mature, and Germinated Somatic Embryos of Cotyledon orbiculata L

Cotyledon orbiculata L. (Crassulaceae)-round-leafed navelwort-is used worldwide as a potted ornamental plant, and it is also used in South African traditional medicine. The current work aims to assess the influence of plant growth regulators (PGR) on somatic embryogenesis (SE) in C. orbiculata; compare the metabolite profile in early, mature, and germinated somatic embryos (SoEs) by utilizing ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS); and determine the antioxidant and enzyme inhibitory potentials of SoEs. A maximum SoE induction rate of 97.2% and a mean number of SoEs per C. orbiculata leaf explant of 35.8 were achieved on Murashige and Skoog (MS) medium with 25 µM 2,4-Dichlorophenoxyacetic acid and 2.2 µM 1-phenyl-3-(1,2,3,-thiadiazol-5-yl)urea. The globular SoEs were found to mature and germinate best on MS medium with gibberellic acid (4 µM). The germinated SoE extract had the highest amounts of both total phenolics (32.90 mg gallic acid equivalent/g extract) and flavonoids (1.45 mg rutin equivalent/g extract). Phytochemical evaluation of SoE extracts by UHPLC-MS/MS reveals the presence of three new compounds in mature and germinated SoEs. Among the SoE extracts tested, germinated SoE extract exhibited the most potent antioxidant activity, followed by early and mature somatic embryos. The mature SoE extract showed the best acetylcholinesterase inhibitory activity. The SE protocol established for C. orbiculata can be used for the production of biologically active compounds, mass multiplication, and conservation of this important species.

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

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.

Recovery of virus-free Almond (Prunus dulcis) cultivars by somatic embryogenesis from meristem undergone thermotherapy

One of the world's main horticulture problems is the contamination of fruit trees with a variety of plant diseases, especially viral and pseudo-viral diseases. Due to the non-sexual propagation of the trees, these diseases have been transmitted to different parts of the world. The main aim of this study was to obtain a new effective method for virus elimination from almond cultivars, which was performed in two phases. In the first phase, we tested various almond cultivars with ELISA and RT-PCR. The results showed the infection of mother plantlets. So, three types of in vitro thermotherapy treatments were performed on infected plants to make them virus-free. The plantlets obtained from 0.5 mm meristem treated with the first type of thermotherapy (TH1: 8 h at 27 °C and 16 h at 38 °C for 18 days) showed the highest percentage of elimination of ApM, ACLS and TRS viruses. In the second phase, meristems were cultured on MS medium containing 0, 0.5, 1 and 2 mg/L 2,4-D with 1 mg/L TDZ and after two weeks, thermotherapy treatments were performed. The results showed, combining three methods of thermotherapy (TH1), meristem culture and somatic embryogenesis induction from meristem on MS medium supplemented with 0.5 mg/L 2,4-D and 1 mg/L TDZ is the most effective and safe technique for virus eradication without meristem size challenges. The samples that were diagnosed as virus-free were proliferated in temporary immersion bioreactor systems, and rooted to be used for later propagation and establishment of mother healthy orchards.

Micropropagation from Inflorescence Nodal Segments of Phalaenopsis and Acclimatization of Plantlets Using Different Substrates

Phalaenopsis is an orchid genus of great economic value in world floriculture. In vitro clonal propagation is the only large-scale feasible method for Phalaenopsis propagation, but it is difficult because of the low multiplication rate. The aim of this study was to evaluate the effect of types and concentrations of N6-benzyladenine (6-BA) and gibberellic acid (GA3) on the in vitro multiplication of shoots from inflorescence nodal segments (INS) of Phalaenopsis hybrids. INS with one axillary bud were inoculated in New Dogashima Medium with different combinations of BA and GA3. The results show that the treatment containing 1.0 mg L−1 BA and 1.5 mg L−1 GA3 showed the higher percentage of live inflorescence segments (71.48%) and a number of shoots (1.68 shoots/INS). The highest 6-BA concentration (4 mg L−1) tested in this study resulted in the best shoot multiplication rate (4.3). Contamination and browning of the INS tissues were the main difficulties identified for clonal propagation of Phalaenopsis. Successful in vitro rooting occurred on half-strength Murashige and Skoog medium (100%), and acclimatization (100%) was obtained independent of the substrates. However, the best gains in number of roots, leaves, chlorophyll content, and fresh weight of plantlets were achieved using vermiculite.

Innovation in Propagation and Cultivation of Ornamental Plants

Ornamental plants are constantly being improved by new technologies and cultivation systems to provide new, high-quality plant material for one of the most demanding markets in the horticulture sector [...]