Embryogenic Suspension Cultures Research Articles

In vitro selection and identification of sweetpotato (Ipomoea batatas (L.) Lam.) plants tolerant to NaCl

In vitro selection of sweetpotato (Ipomoea batatas (L.) Lam.) plants tolerant to NaCl was achieved using embryogenic suspension cultures of sweetpotato cv. Lizixiang and gamma-ray induced mutation. Cell aggregates from embryogenic suspension cultures of Lizixiang were irradiated with 80 Gy gamma-ray, and 1 week after irradiation they were cultured in a selective medium containing 342 mM NaCl for in vitro selection. A total of 276 plants were regenerated from the irradiated 2,783 cell aggregates by a two-step in vitro selection procedure. After the regenerated plants were propagated into plant lines on the basal medium, they were cultured on the medium supplemented with 86, 171, 257 and 342 mM NaCl, respectively, in order to evaluate their in vitro salt tolerance. Of them 18 plant lines showed significantly higher in vitro salt tolerance than control plants. Proline and superoxide dismutase (SOD) were more accumulated in these 18 plant lines than in control plants when both were exposed to NaCl. Salt tolerance of the 18 plant lines was further evaluated with Hoalgland solution containing different concentrations of NaCl in a greenhouse. The results indicated that 3 of them had significantly better growth and rooting ability than the remaining 15 plant lines and control plants at 171 mM NaCl.

Somatic embryogenesis, embyogenic cell suspension from Ocimum sanctum leaf callus cultures and its rosmarinic acid accumulation

The accumulation of rosmarinic acid (RA) in Ocimum sanctum (L.) somatic embryogenic callus and its cell suspension cultures was investigated. For callus induction, leaves, stems and inflorescence explants excised from field-grown plants were cultured on Murashige and Skoog (MS) medium containing 2,4-D (1 mg l-1) combined with kinetin (0.1-0.5 mg l-1), 2,4-D (0.5-2.5 mg l-1) individually, IAA (0.5-2.5 mg l -l) individually, and NAA (0.5-2.5 mg l -l) individually. Due to better proliferation ability and high RA content of leaf callus, it was chosen to induce somatic embryogenesis by supplementing with different concentration and combination of BAP + NAA + kinetin. Among the different combination tested, BAP (1 mg l -l) + NAA (1 mg l -l) + kinetin (0.5 mg l -l) exhibited a maximum embryogenic potential (73%) and number of globular embryo (34.3) per callus. In order to study the RA production, the proliferation of embryogenic suspension culture was tested by transferring embyogenic callus at stationary growth phase from MS solid to liquid medium containing the same composition and hormonal concentration. After five subcultures, the suspensions were maintained continuously for six weeks without subculturing. Suspension cultures showed progressive callus growth and RA accumulation throughout the experimental period. The highest RA (82.1 mg l -1) content and biomass growth (11.6 g l -1) was observed in the cultures supplemented with BAP (1 mg l -l) + NAA (1 mg l -l) + kinetin (0.5 mg l -l). It was 40 fold higher than the leaf callus.

Generation of Recombinant Antibodies against Orchardgrass Acidic nsLTP-Like Proteins

Embryogenic and non-embryogenic suspension cultures of orchardgrass (Dactylis glomerata L.) secreted into the culture medium a set of proteins, among which low molecular mass (11/12 kDa) proteins were found. However, only the 11/12 kDa proteins from the embryogenic suspension cultures reacted specifically with an antiserum raised against the carrot EP2 non-specific lipid transfer protein (nsLTP). Two-dimensional (2-D) electrophoretic analysis revealed that the extracellular nsLTP-like proteins from the embryogenic lines were acidic proteins, with pI values ranging between 4.3 and 6.4, and the 11/12 kDa proteins of the non-embryogenic lines were basic ones (pI 8-9.3). This is only the second case to report on the accumulation of extracellular acidic nsLTP-like proteins in the culture medium during somatic embryogenesis. A naive phage display Griffin1. library was used to select single-chain phage antibodies, which specifically bind to acidic nsLTP-like proteins. Nine phage clones were selected after four rounds of biopanning of the target proteins blotted on a nitrocellulose membrane. Three soluble monoclonal single-chain phage antibodies, expressed in the non-suppressor E. coli strain HB2151, were purified by metal affinity chromatography and found to be highly specific for the acidic nsLTP-like proteins from the embryogenic suspension cultures. The application of the selected monoclonal antibodies for localization and elucidation of the role of the acidic nsLTP-like proteins in vivo is discussed.

In vitro plant regeneration from embryogenic cell suspension culture of Astragalus chrysochlorus (Leguminoseae)

In vitro plant regeneration was achieved from embryogenic cell suspension culture of Astragalus chrysochlorus. When 30-day-old aseptically grown seedlings were cultured on Murashige and Skoog (MS) medium containing 0.1 mg/l -naphthaleneacetic acid (NAA) plus 1.0 mg/l 6-benzyladenine (BA), friable callus was formed within two weeks from the mesocotyl of the seedling. After three weeks, proliferated actively growing calli were transferred to MS liquid medium containing 2,4- dichlorophenoxyacetic acid (2,4-D), indole-3-acetic acid (IAA) or NAA and subcultured at two week intervals. After two weeks, induction of somatic embryos up to the torpedo stage occured at all tested concentrations of 2,4-D, IAA or NAA. Somatic embryos developed only in MS medium containing 0.5 mg/l IAA within two weeks and 2% of globular embryos were developed into the cotyledonary stage embryos. Eighty one percent of somatic embryos cultured in MS medium supplemented with 0.5 mg/l IAA were found to be diploid by flow cytometric analysis. Plantlet propagation was achieved on half strength MS liquid medium supplemented with 3% (w/v) sucrose after four weeks of culture. After a month on half strength MS medium [1.5% (w/v) sucrose and 0.8% (w/v) agar] 29 of 71 shoots developed into rooted plantlets.

Plant regeneration from suspension cells induced from hypocotyls derived from interspecific cross Alstroemeria pelegrina × A. magenta and transformation with Agrobacterium tumefaciens

Embryogenic cell suspension cultures were established using the ovule culture of an interspecific cross, Alstroemeria pelegrina var. rosea × A. magenta. Ovules harvested 14 days after pollination were cultured on Murashige and Skoog (MS) medium without plant growth regulators (PGRs); calli were produced on the hypocotyl surface in germinating zygotic embryos. Suspension cells were induced from the calli by using liquid MS media containing 2,4-dichlorophenoxyacetic acid or 4-amino-3,5,6-trichloropyridine-2-carboxylic acid (picloram). Adventitious embryos developed from the suspension cells on half-strength MS medium supplemented with 0.5 mg l−1 of both α-naphthaleneacetic acid and N6-benzylaminopurine; they grew into plantlets on the same medium. The plantlets formed rhizomes following transfer to half-strength MS medium without PGRs, and acclimatized plants were easily established. Subsequently, Agrobacterium-mediated transformation system was applied. The suspension cells were co-cultivated with A. tumefaciens strain EHA101/pIG121Hm or LBA4404/pTOK233, both of which contain neomycin phosphotransferase II, hygromycin phosphotransferase and intron-containing ß-glucuronidase (intron-GUS) genes. Seven days after co-cultivation, the cells were subjected to GUS assay; staining was most pronounced in the cells subcultured in a picloram-containing liquid medium and co-cultivated with EHA101/pIG121Hm. The co-cultivated cells were transferred to the MS medium containing picloram and 20 mg l−1 hygromycin; 1 month later, several hygromycin-resistant callus lines showing GUS activity were obtained. Transgenic plants were obtained through our plant regeneration system, and foreign gene insertion into the regenerated plants was confirmed by polymerase chain reaction.

High frequency plant regeneration from zygotic-embryo-derived embryogenic cell suspension cultures of watershield (Brasenia schreberi)

An improved protocol for high frequency plant regeneration via somatic embryogenesis from zygotic embryo-derived cell suspension cultures of watershield (Brasenia schreberi) was developed. Zygotic embryos formed pale-yellow globular structures and white friable callus at a frequency of 80% when cultured on half-strength MS medium supplemented with 0.3 mg l−1 2,4-D. However, the frequency of formation of pale-yellow globular structures and white friable callus decreased slightly with increasing concentrations of 2,4-D up to 3 mg l−1, where the frequency reached ~50% of the control. Cell suspension cultures from zygotic embryo-derived white friable callus were established using half-strength MS medium supplemented with 0.3 mg l−1 2,4-D. Upon plating of cell aggregates on half-strength MS basal medium, approximately 8.3% gave rise to somatic embryos and developed into plantlets. However, the frequency of plantlet development from cell aggregates was sharply increased (by up to 55%) when activated charcoal and zeatin were applied. Regenerated plantlets were successfully transplanted to potting soil and grown to normal plants in a growth chamber. The distinctive feature of this study is the establishment of a high frequency plant regeneration system via somatic embryogenesis from zygotic embryo-derived cell suspension cultures of watershield, which has not been previously reported. The protocol for plant regeneration of watershield through somatic embryogenesis could be useful for the mass propagation and transformation of selected elite lines.

Studies on Agrobacterium-mediated genetic transformation of embryogenic suspension cultures of sweet potato

In this study, genetic transformation of embryogenic suspension cultures of sweet potato (Ipomoea batatas) cultivar Xu55-2 was conducted utilizing the Agrobacterium tumefaciens strain EHA105 that contains the binary vector pBIN19/SBD2 with SBD2 (starch binding domain 2) gene and neomycin phosphotransferase (NPT II) gene. The presence of the SBD2 gene in the genomic DNA of transgenic plants was verified by PCR amplification and confirmed by Southern blot analysis. Results suggested that cefotaxime (Cefo), at the concentration of 200 mg/L, was able to effectively suppress the growth of Agrobacterium after co-cultivation. The optimal concentration for kanamycin (Kan) was 10 mg/L for selecting resistance calli, somatic embryo formation and plant regeneration. The highest frequency of shoot induction (30.9%) was obtained on the MS medium containing 10 mg/L Kan, 200 mg/L Cefo, 1.0 mg/L abscisic acid (ABA) and 1.0 mg/L gibberellic acid (GA3).

STUDI PERBANDINGAN METODE TRANSFORMASI DNA MENGGUNAKAN VEKTOR Agrobacterium tumefaciens PADA TANAMAN TEBU (Sacharum hybrid)

In order to compare transient expression of gus gene driven by CaMV 35S and rice ubiquitin RUBQ2 promoters, a DNA transformation was conducted using embryogenic callus and suspension cultures of sugarcane. The transient gus expression was observed by histochemical staining method. The histochemical observation of GUS activity after co-cultivation showed that RUBQ2 promoter produced high level of clear blue spots both in embryogenic callus and suspension cultures, while the CaMV35S promoter was not detected. The suspension cultures slightly increased transient gus gene expression compared to embryogenic callus. However, the histochemical analysis of regenerated putative transformant plants after 5 successive cycles on the selection medium showed no blue spots of gus gene expression. PCR amplification of DNA for CaMV35 or nptII in putative transformant plants confirmed that there was no integration of the transformed gene in the genome DNA. The results suggested a possibility of somaclonal variation with callus propagation, thus did not produce transformed plants. To avoid the somaclonal variation, the transformation was conducted using in vitro plants and multiple shoots without intervening callus phase. Histochemical observation of infected materials after co-cultivation showed that almost all of the infected materials partially exhibited blue color in the basal region. In case of in vitro plants, they rapidly grow and multiplied in the selection medium, thus the method provided an excellent system for the transformation in sugarcane. The results suggest that in vitro plants as well as multiple shoots need further investigation to be used as target tissues for Agrobacteriummediated transformation in sugarcane.

Agrobacterium-mediated genetic transformation of embryogenic cell suspension cultures of Santalum album L.

An efficient method for Agrobacterium-mediated genetic transformation of embryogenic cell suspension cultures of Santalum album L. is described. Embryogenic cell suspension cultures derived from stem internode callus were transformed with Agrobacterium tumefaciens harbouring pCAMBIA 1301 plant expression vector. Transformed colonies were selected on medium supplemented with hygromycin (5 mg/l). Continuously growing transformed cell suspension cultures were initiated from these colonies. Expression of β-glucuronidase in the suspension cultures was analysed by RT-PCR and GUS histochemical staining. GUS specific activity in the transformed suspension cultures was quantified using a MUG-based fluorometric assay. Expression levels of up to 105,870 pmol 4-MU/min/mg of total protein were noted in the transformed suspension cultures and 67,248 pmol 4-MU/min/mg of total protein in the spent media. Stability of GUS expression over a period of 7 months was studied. Plantlets were regenerated from the transformed embryogenic cells. Stable insertion of T-DNA into the host genome was confirmed by Southern blot analysis. This is the first report showing stable high-level expression of a foreign protein using embryogenic cell suspension cultures in S. album.

Methyl jasmonate induced overproduction of eleutherosides in somatic embryos of Eleutherococcus senticosus cultured in bioreactors

This study was concentrated on the production of eleutherosides and chlorogenic acid in embryogenic suspension cultures of Eleutherococcus senticosus by exposing them to different concentrations (50-400 µM) of methyl jasmonate (MJ) during the culture period. In the bioreactor cultures, eleutheroside content increased significantly by elicitation of MJ, however, the fresh weight, dry weight and growth ratio of embryos was strongly inhibited by increasing MJ concentrations. The highest total eleutheroside (7.3 fold increment) and chlorogenic acid (3.9 fold increment) yield was obtained with 200 µM MJ treatment. There was 1.4, 3.4 and 14.9 fold increase in the eleutheroside B, E, and E1 production respectively with such elicitation treatment. These results suggest that MJ elicitation is beneficial for eleutheroside accumulation in the embryogenic cell suspension cultures.

Efficient Agrobacterium tumefaciens-mediated transformation using embryogenic suspension cultures in sweetpotato, Ipomoea batatas (L.) Lam.

Efficient Agrobacterium tumefaciens-mediated transformation was achieved using embryogenic suspension cultures of sweetpotato (Ipomoea batatas (L.) Lam.) cv. Lizixiang. Cell aggregates from embryogenic suspension cultures were cocultivated with the A. tumefaciens strain EHA105 harboring a binary vector pCAMBIA1301 with gusA and hygromycin phosphotransferase II gene (hpt II) genes. Selection culture was conducted using 25 mg l−1 hygromycin. A total of 2,218 plants were regenerated from the inoculated 1,776 cell aggregates via somatic embryogenesis. β-glucuronidase (GUS) assay and PCR, dot blot and Southern blot analyses of the regenerated plants randomly sampled showed that 90.37% of the regenerated plants were transgenic plants. The number of integrated T-DNA copies varied from 1 to 4. Transgenic plants, when transferred to soil in a greenhouse and a field, showed 100% survival. No morphological variations were observed in the ex vitro transgenic plants. These results exceed all transformation experiments reported so far in the literature in quantity of independent events per transformation experiment in sweetpotato.

Increased eleutheroside production in Eleutherococcus sessiliflorus embryogenic suspension cultures with methyl jasmonate treatment

The effects of methyl jasmonate elicitation were investigated in embryogenic suspension cultures of Eleutherococcus sessiliflorus in bioreactors for the production of eleutherosides and chlorogenic acid. Eleutherosides and chlorogenic acid increased with methyl jasmonate elicitation (in the range 50–400 μM); however, fresh weight, dry weight and growth ratio of the cells were inhibited by increasing methyl jasmonate concentration. There were 3.5-, 2.6-, 2.5- and 3.2-fold increments in eleutherosides B, E, E1 and chlorogenic acids were evident, respectively, with 200 μM methyl jasmonate treatment. These results suggest that methyl jasmonate elicitation is beneficial for eleutheroside accumulation in the embryogenic suspension cultures.

Somatic embryogenesis and plant regeneration of litchi (Litchi chinensis Sonn.) from leaves of mature phase trees

Embryogenic cultures were induced from leaflets from new vegetative flushes of mature ‘Brewster’ litchi trees on B5 medium containing 400 mg l−1 glutamine, 200 mg l−1 casein hydrolysate, 30 g l−1 sucrose, 4.52 μM 2,4-D, 9.30 μM kinetin and 3 g l−1 gellan gum in darkness. Embryogenic cultures consisting of proembryonic cells and masses were maintained either on semi-solid MS medium supplemented with 4.52 μM 2,4-D and 0.91 μM zeatin or as embryogenic suspension cultures in liquid medium of the same composition. Maturation of somatic embryos occurred on semi-solid MS medium with 5–20% (v/v) filter-sterilized coconut water in darkness. Recovery of plants from somatic embryos was improved with 14.4 μM GA3 on half-strength MS medium with 0.2 g l−1 activated charcoal under a 16 h photoperiod provided by cool white fluorescent lights (60–80 μmol s−1 m−2). Plants have been successfully acclimatized in the greenhouse.

Arabinogalactan-proteins stimulate the organogenesis of guard cell protoplasts-derived callus in sugar beet

Arabinogalactan proteins (AGPs) represent a class of proteoglycans implicated in the development and differentiation of cells and tissues both in planta and in vitro. Here we report that AGP-rich extracts isolated from media of embryogenic and non-embryogenic suspension cultures of sugar beet (Beta vulgaris L.) are able to enhance the organogenesis of guard protoplast-derived callus and to increase the number of shoots formed, in comparison to control cultures. Immunocytochemical detection of carbohydrate antigens in the extracts revealed the presence of epitopes that typify both AGP and pectin, the latter being frequently bound to AGPs or, in some cases, even contributing to the polysaccharide structure of proteoglycan molecules. The most abundant epitopes proved to be those recognized by the JIM13, LM2, and MAC207 antibodies, whereas some others could be found only in relatively small or trace amounts--these included epitopes recognized by JIM16, JIM5, and LM6. Surprisingly, the JIM4- and JIM8-binding epitopes that are expressed in the course of in vitro morphogenetic processes of many species could not be detected at all in sugar beet AGPs. This is the first report of the improvement of sugar beet protoplast-derived callus organogenesis by exogenous AGP-rich extracts, an achievement that will have great impact on the biotechnological applications of protoplast technology in this species.

ISOLATION AND CULTURE OF GRAPE PROTOPLASTS FROM EMBRYOGENIC SUSPENSION CULTURES AND LEAVES OF VITIS VINIFERA AND VITIS ROTUNDIFOLIA

ISHS International Symposium on Biotechnology of Temperate Fruit Crops and Tropical Species ISOLATION AND CULTURE OF GRAPE PROTOPLASTS FROM EMBRYOGENIC SUSPENSION CULTURES AND LEAVES OF VITIS VINIFERA AND VITIS ROTUNDIFOLIA

Effect of 2,4-d, glutamine and BAP on embryogenic suspension culture of date palm (Phoenix dactylifera L.)

The proliferation of embryogenic suspension culture in two cultivars (Jihel and Bousthami Noir) of Phoenix dactylifera L. was tested on liquid media with or without 2,4-d and with different glutamine concentrations (3.35 × 10−4, 6.7 × 10−4 and 13.4 × 10−4 M). The liquid medium with 0.1 mg l−1 2,4-d and 6.7 × 10−4 M glutamine has clearly improved the proliferation of somatic embryos. In fact, when glutamine concentration increased from 3.35 × 10−4 to 6.7 × 10−4 M, the yield of somatic embryos increased from 14 to 56 embryos per 100 ml of culture medium for “Jihel” cultivar and 25–71 embryos per 100 ml of culture medium for “Bousthami Noir” cultivar. In contrast, increasing glutamine concentration from 6.7 × 10−4 to 13.4 × 10−4 M, the embryos yield was negligible. Based on biochemical analysis, the highest accumulation of proteins and sugars was obtained in liquid medium with 0.1 mg l−1 2,4-d and 6.7 × 10−4 M glutamine (118 and 91 mg of proteins g−1 DW, respectively, for “Jihel” and “Bousthami Noir” cultivars; 194 mg of sugars g−1 DW for “Jihel” cultivar and 182 mg of sugars g−1 DW for “Bousthami Noir” cultivar). In addition, the supply of 0.05 mg l−1 BAP on the germination medium could be useful in terms of germination percentage of somatic embryos. When BAP concentration increased from 0.05 to 0.2 mg l−1, the germination percentage of somatic embryos decreased from 14.2 to 4.9%, while secondary embryogenesis increased from 26.4 to 45.2%.

Specificity of expression of the GUS reporter gene ( uidA) driven by the tobacco ASA2 promoter in soybean plants and tissue cultures

Twelve independent lines were transformed by particle bombardment of soybean embryogenic suspension cultures with the tobacco anthranilate synthase (ASA2) promoter driving the uidA (beta-glucuronidase, GUS) reporter gene. ASA2 appears to be expressed in a tissue culture specific manner in tobacco (Song H-S, Brotherton JE, Gonzales RA, Widholm JM. Tissue culture specific expression of a naturally occurring tobacco feedback-insensitive anthranilate synthase. Plant Physiol 1998;117:533-43). The transgenic lines also contained the hygromycin phosphotransferase (hpt) gene and were selected using hygromycin. All the selected cultures or the embryos that were induced from these cultures expressed GUS measured histochemically. However, no histochemical GUS expression could be found in leaves, stems, roots, pods and root nodules of the plants formed from the embryos and their progeny. Pollen from some of the plants and immature and mature seeds and embryogenic cultures initiated from immature cotyledons did show GUS activity. Quantitative 4-methylumbelliferyl-glucuronide (MUG) assays of the GUS activity in various tissues showed that all with observable histochemical GUS activity contained easily measurable activities and leaves and stems that showed no observable histochemical GUS staining did contain very low but measurable MUG activity above that of the untransformed control but orders of magnitude lower than the constitutive 35S-uidA controls used. Low but clearly above background levels of boiling sensitive GUS activity could be observed in the untransformed control immature seeds and embryogenic cultures using the MUG assay. Thus in soybean the ASA2 promoter drives readily observable GUS expression in tissue cultures, pollen and seeds, with only extremely low levels seen in vegetative tissues of the plants. The ASA2 driven expression seen in mature seed was, however, much lower than that seen with the constitutive 35S promoter; less than 2% in seed coats and less than 0.13% in cotyledons and embryo axes. The predominate tissue culture specific expression pattern of the ASA2 promoter may be useful for genetic transformation of crops.

Triploid banana cell growth phases and the correlation of medium pH changes with somatic embryogenesis in embryogenic cell suspension culture

Embryogenic cell suspensions of Musa AAA and AAB genomic groups were cultured in a maintenance culture medium for 17 generations (lasting for 238 days). The cell growth phases and medium pH changes were also observed correspondingly. Three major growth phases of AAA genomic group have been focused, namely cell releasing, proliferation and globularization phases. During almost all the subculture generations the cell stocks of AAB ‘Raja’ were continuously characterized by proliferating cell aggregates while the globularization phase occurred only for short duration. The medium acidity levels of the cell stocks of AAA ‘Pei-Chiao’ and ‘Robusta’ were commonly scattered in a wider range of pH 3.3–5.3, while the AAB ‘Raja’ were deviated in a narrow range of pH 4.0–4.6. After subculture, culture medium showed biphasic pH changes, which were drastic pH falls followed by an auto-regulated steady-state level. The steady-state pH values in each of the three growth phases (i.e. cell releasing, proliferation and globularization phases) were of 3.3–4.0, 4.0–4.8 and 4.8–5.3 respectively. Morphological bipolarity and the efficiency in the formation of somatic embryos have been thoroughly discussed. Reported research indicates that the condition of pH below 4.6 may prevent the development of embryogenic cells towards polar growth.

Regeneration of plants from Ipomoea cairica L. protoplasts and production of somatic hybrids between I. cairica L. and sweetpotato, I. batatas (L.) Lam.

Plants were regenerated from mesophyll protoplasts of Ipomoea cairica L., a wild relative of sweetpotato (Ipomoea batatas (L.) Lam.), and somatic hybrids between I. cairica L. and sweetpotato cv. Xushu 18 were obtained by PEG-mediated method. I. cairica L. protoplasts were isolated from the leaves of in vitro grown plants and cultured in a modified MS medium containing 0.05 mg l−1 2,4-D and 0.5 mg l−1 kinetin. Nine weeks after plating, the obtained small calluses up to about 2 mm in diameter were transferred to solid MS medium supplemented with 0.05 mg l−1 2,4-D and 0.5 mg l−1 kinetin for callus proliferation. Three weeks after transfer, the calluses were transferred to MS medium supplemented with 0–1.0 mg l−1 IAA and 1.0–3.0 mg l−1 BAP and further to hormone-free MS medium for plant regeneration. The frequencies of calluses forming plants ranged from 6.0% to 41.3% based on the different concentrations of IAA and BAP, and 2.0 mg l−1 BAP gave the highest regeneration frequency of protoplast-derived calluses in I. cairica L.. The regenerated plants, when transferred to soil, showed 100% survival. No morphological variations were observed. Mesophyll protoplasts of I. cairica L. were fused with protoplasts isolated from embryogenic suspension cultures of Xushu 18 by PEG-mediated method. The fused products were cultured with the best protoplast culture system of I. cairica L.. Finally, 114 plants were produced from 63 of the 182 calluses derived from the fused protoplasts, and 46 plants of them were confirmed to be somatic hybrids through peroxidase isozyme, RAPD, morphological and cytological analyses.

CRYOPRESERVATION OF EMBRYOGENIC SUSPENSION CULTURES OF CYCLAMEN PERSICUM MILL.

We have developed a protocol for the cryopreservation of embryogenic suspension cultures of Cyclamen persicum, which does not involve the need of sophisticated equipment. With the aim of achieving this simple protocol for cryopreservation, different cryoprotectants in the pre-culture and pre-treatment periods on cell growth and re-growth after cryopreservation were tested. For cryopreservation experiments embryogenic suspension cultures in the linear growth phase 7-10 days after subculture were used. Of the different cryoprotectants tested during a 2-day pre-culture, 0.6 M sucrose resulted in the highest re-growth rate of 75% based on the number of Petri dishes plated after thawing. Additionally, a pre-treatment with 0.6 M sucrose and 10% DMSO (dimethylsulfoxide) for 1 h immediately prior to freezing, also positively affected re-growth. Experiments in which the optimal pre-culture duration was varied showed that 2-4 days was the best exposure time to 0.6 M sucrose. Callus re-grown after cryopreservation showed growth rates similar to that of unfrozen callus and regenerated even higher numbers of somatic embryos than unfrozen control callus. Microscopic studies on viability using FDA (fluorescein diacetate) staining revealed that only few small embryogenic cells survived cryopreservation, while vacuolated single cells died.