Production of synthetic seed by desiccation and encapsulation
Producing synthetic seed of carrot consists of coating in-vitro grown embryos with a synthetic seed coat such as Polyox WSR-N
750, drying under controlled conditions, and hardening to prevent precocious germination. Survival of such embryos declines
over time. Similar procedures have also been used with celery. Somatic embryos have several advantages compared to conventional
tissue culture which include proliferacy, singulation, and the development of bipolar structures. The factors which most limit
the use of synthetic seeds are the inability to use such procedures with economically important genotypes, lack of understanding
of the maturation of somatic embryos and poor conversion rates to greenhouse and/or field.
Available from: David J Merritt
- "An advantage of this technique over vitrification lies in its use of nontoxic materials. The encapsulation-dehydration technique was initially developed for the production of artificial seeds (Janick et al. 1989) and was adapted for the cryopreservation of Solanum shoot tips by Fabre and Dereuddre (1990). Over the past decade, it has also been found to be effective in the cryopreservation of orchid seeds (Wood et al. 2000; Flachsland et al. 2006; Surenciski et al. 2007; Sommerville et al. 2008), orchid protocorms (Maneerattanarungroj et al. 2007; Jitsopakul et al. 2008; Gogoi et al. 2013), protocormlike bodies (Poobathy et al. 2009; Antony et al. 2011; Yin et al. 2011), and shoot tips (Lurswijidjarusa and Thammasiri 2004). "
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ABSTRACT: Premise of research. Orchids are among the most enigmatic of plant species. Yet the Orchidaceae comprises more species at risk of extinction than any other plant family. The collection and storage of orchid germplasm—principally seeds and associated mycorrhizal fungi but also protocorm-like bodies using encapsulation and vitrification techniques—allows for secure ex situ conservation. This article reviews the approaches and techniques used for the ex situ conservation of orchid germplasm, with a focus on seed banking and the use of cryopreservation techniques to improve the longevity of germplasm.
Pivotal results. It is increasingly apparent that cryopreservation—the storage of germplasm at ultra-low temperatures (e.g., in liquid nitrogen)—is required for the long-term and low-maintenance conservation of all types of orchid germplasm. For orchid seeds, desiccation tolerance is common, but longevity in storage is poor. Cryopreservation of orchid seeds shows promise, but some complexities in low-temperature storage behavior still require explanation and resolution. The application of more advanced cryopreservation techniques, including encapsulation-dehydration and vitrification, is becoming increasingly common. These techniques provide for the simultaneous storage of orchid propagules with their compatible fungus, while for seeds, vitrification techniques show potential for improving tolerance to the stresses of cryopreservation.
Conclusions. A renewed focus on describing the low-temperature storage physiology of orchid seeds to more precisely define the relationship between seed water content, storage temperature, and seed survival is required, as is perhaps the wider adoption of the use of cryoprotectants for seeds. This research, coupled with the development of improved methods of seed viability testing, will support the growing work of germplasm banks to protect orchid biodiversity in the face of habitat loss and potential species extinction.
Available from: hortsci.ashspublications.org
- "Somatic embryogenesis induced from mature somatic tissue is a desirable means of rapid vegetative propagation (Ammirato, 1983; Janick et al., 1989). This study was undertaken to determine the feasibility of inducing somatic embryos from sporophytic tissue of carnation, a species, to our knowledge , for which somatic embryogenesis has not been reported previously, Stock plants of 'Scania', 'Improved White Sim', and 'Sandra' carnation were maintained in a greenhouse at 16C (days) and 10C (nights) with supplemental light from incandescent bulbs to interrupt winter nights. "
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- "multiple range test, P = 0.05. The increased tolerance to partial desiccation induced by ABA was consistent in all five experiments (Figs. 1 and 2, Table 1) and confirms previous studies with celery (Kim and Janick, 1989), carrot (Daucus carota L.) (Kitto and Janick, 1985b), and alfalfa (Medicago sativa L.), for which application at the late embryo production phase was critical (Senaratna et al., 1990). Our results show clearly that embryos were the most receptive to induction of desiccation tolerance by ABA in the last 2 days of culturing (Table 1). "
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ABSTRACT: Tolerance to partial desiccation and amino acid composition of celery (Apium graveolens L. cv. SB 12) somatic embryos were investigated under various culture durations and with exogenous application of 1 µM ABA, proline, and/or γ γ -aminobutyrate (GABA). ABA consistently increased tolerance to partial desiccation and elevated proline and GABA content of embryos. The changes in tolerance to partial desiccation associated with changes in culture duration (optimum 9 to 10 days) correlated with embryo proline content. Exogenous proline increased embryo proline content and tolerance to partial desiccation. Exogenous GABA increased embryo GABA content and tolerance to partial desiccation only when applied in combination with proline. Chemical name used: abscisic acid (ABA). Desiccated somatic embryos have been proposed as a poten-tial analog of true seed (Gray and Purohit, 1991; Gray et al., 1987; Janick et al., 1989; Kitto and Janick, 1985a). A key factor for the production of such synthetic seed is the ability of somatic embryos to survive desiccation and convert into normal seed-lings. Several factors have been reported to increase desiccation tolerance of somatic embryos. These include a slow desiccation rate (Gray et al., 1987; Kim and Janick, 1989), supplementation of embryo production medium (EPM) with ABA (Kitto and Janick, 1985b; Senaratna et al., 1990), proline (Rim and Janick, 1990, 1991) or high sucrose concentration, chilling, or high culture density (Kitto and Janick, 1985b). Little is known about the manner by which these treatments induce desiccation tol-erance, and it may be that some, if not all, of these factors activate a single physiological mechanism. For example, me-dium supplementation with ABA, known to induce proline ac-cumulation (LaRosa et al., 1987), and exogenous proline may both be inducing desiccation tolerance by elevating embryo pro-line content. The objective of this study was to investigate the relationship between changes in tolerance to partial desiccation of somatic celery embryos and amino acid composition. Changes in tol-erance were induced by altering culture duration and supple-mentation of medium with ABA, proline, and/or GABA.
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