Somatic embryogenesis and plant regeneration from immature zygotic embryos of papaya (Carica papaya L.)

Summary Immature zygotic embryos from open-pollinated and selfed Carica papaya L. fruits, 90 to 114 days post-anthesis, produced 2 to 20 somatic embryos on apical domes, cotyledonary nodes, and radicle meristems after culture for three weeks on half-strength Murashige and Skoog (MS) medium supplemented with 0.1 to 25 mg l^–1 2,4-dichlorophenoxyacetic acid (2,4-D), 400 mg l^–1 glutamine, and 6% sucrose. After six weeks of culture, about 40 to 50% of the zygotic embryos had become embryogenic, and each embryogenic embryo yielded hundreds of somatic embryos within five months of culture on media supplemented with 2,4-D. Somatic embryos matured on half-strength MS medium, germinated on MS medium containing 5 mg l^–1 kinetin, and grew large enough for greenhouse culture on MS medium. Shoots were rooted in vermiculite and grown in the greenhouse.Journal Series no. 3449 of the Hawaii Institute of Tropical Agriculture and Human Resources     

Somatic embryogenesis and plant regeneration from shoot-tip explants inPhoenix dactylifera L.

For maximum avoidance of somaclonal variation risks, the commonly used medium for somatic embryogenesis inPhoenix dactylifera has been lowered in growth regulators and activated charcoal. When initially cultured on MS basal medium containing only 150 mg dm^?3 charcoal, 5 mg dm^?3 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg dm^?3 benzylaminopurine (BAP), 10 to 20% of shoot-tip explants developed into embryogenic calli. The embryogenic potential has been maintained for over 24 months with no decline. In addition, this medium has been found to be more efficient than conventionaly one containing 3 g dm^?3 charcoal, 100 mg dm^?3 2,4-D and 3 mg dm^?3 2-isopentyladenosine (2IP). Plantlet regeneration was achieved when somatic embryos were subcultured to medium with 0.1 mg dm^?3 2,4-D and 0.5 mg dm^?3 BAP or without growth regulators.     

Somatic embryogenesis and plant regeneration from immature embryo explant of papaya (Carica papaya L. cv. washington and honey dew)

Immature zygotic embryo explants of Carica papaya were cultured on MS medium supplemented with 2,4-D (2.0 mg/l) and formed globular embryos on explants without callus formation in 4-6 weeks. Maturation and conversion of somatic embryos was also achieved on the same medium. Cotyledonary stage embryos germinated to 63.66 and 68.33% in cv. honey dew and washington respectively in MS basal medium supplemented ABA (0.5 microm/l). Robust development and proliferation of plantlet roots in vitro was obtained on MS basal medium. Hardened plantlets have 60% survival rate.     

High efficiency plant regeneration from petiole explants of Carica papaya L. through organogenesis

Callus cultures were obrained from petiole explants of Carica papaya on MS medium containing 0.5–10.5 μM α-naphthaleneacetic acid (NAA) in combination with 0.5–5 μM benzyladenine (BA). Hard-green calli were transferred to MS medium containing 100 mgl⁻¹ casein hydrolysate (CH) with specific BA-NAA formulation, where they developed adventitious buds within 2 weeks of culture. Maximum number of adventitious buds were obtained in 2 μM BA and 0.1 μM NAA. Shoot regeneration occurred from these adventitious buds by the end of the 4th week. Regenerated shoots were elongated in hormone-free medium and rooted in half-strength MS fortified with 3 UM NAA and 0.5 μM gibberellic acid (GA₃). The regenerants were transferred to soil after acclimatization.     

Somatic embryogenesis and plant regeneration from stem explants of Moricandia arvensis

Efficient and reproducible plant regeneration has been established from stem internode explants of Moricandia arvensis, a crucifer of special interest due to its C₃-C₄ intermediate photosynthetic activity. Somatic embryogenesis was induced in one-third of explants cultured on Murashige and Skoog based medium containing 9 mm 2,4-dichlorophenoxyacetic acid. High frequencies of plant regeneration (>90%) resulted when somatic embryos were germinated on medium lacking growth regulators. Regenerated plants were diploid, fertile and morphologically similar to seed-derived plants of M. arvensis. This is the first report of somatic embryogenesis in M. arvensis. This plant regeneration system should facilitate gene identification and localisation studies of C₃-C₄ physiology by insertional mutagenesis, a prerequisite for the isolation and transfer of genes involved in C₃-C₄ metabolism from Moricandia to cultivated brassicas. Received: 28 November 1996 / Revision received: 30 January 1997 / Accepted: 15 February 1997     

Somatic embryogenesis and plant regeneration inPisum sativum L.

Somatic embryogenesis was induced in immature zygotic embryos of pea (Pisum sativum L.), synthetic auxins α-naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram, PIC) being used. Only one (line HM-6) of 46 genotypes tested exhibited good potential for somatic embryogenesis. 2,4-D was found as the best somatic embryo inductor. Three different ways of somatic embryo conversion have been described. Plantlets from individual somatic embryos were micropropagated as somaclones and subsequently rooted. A sterile morphological mutant has been found within a group of fertile plants of T₀-generation. Sufficient amount of T₁-seeds is available for somaclonal variation studies.     

Somatic embryogenesis and plant regeneration in Gloriosa L

Friable callus was initiated from shoot apices of Gloriosa superba L. on basal MS medium supplemented with 2, 4-D (4mg L(-1)) + Kn(5 mg L(-1)) + CH(10 mg L(-1)) + CW(20%). Subculture of callus on the same medium after 4-5 weeks showed induction of large number of somatic embryos, which was confirmed with histological studies. Development of embryoids in plantlet took place when the embryogenic callus was transferred to basal MS medium supplemented with BAP (5 mg L(-1)), CH(50 mg L(-1)) +CW(20%). Roots were developed by subculturing them on to the medium containing Kn or BAP (5 mg L(-1)) and IBA (4 mg L(-1)). Plantlets were successfully transferred to pots containing mixture of soil, sand and farmyard manure (2:1:1).     

Somatic embryogenesis and plant regeneration in Medicago arborea L.

Summary An efficient plant regeneration system employing cotyledons, hypocotyls, petioles and leaves as explants and characterized by continuous and prolific production of somatic embryos, has been developed with Medicago arborea ssp. arborea. The optimal somatic embryogenic response was obtained using a two-step protocol, where explants were incubated under a 16 h photoperiod for 2 mo. on Murashige and Skoog (MS) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D; 9 μM) and kinetin (9 μM), and followed by transfer to kinetin-free MS medium with 2,4-D (2.25 μM). Removal of the cytokinin and a reduction in the concentration of auxin (2.25 μM) in the second step of culture were critical for enhanced production of somatic embryos. The best explants proved to be cotyledons and petioles (i.e. a mean of 18.0±0.70 somatic embryos at 3 mo. for petiole culture). Somatic embryos were converted into normal plantlets (8.0±0.89%) when cultured on basal MS medium with 5 μM indolebutyric acid. No somatic embryos were obtained when thidiazuron was used in the culture media. Using petioles as explants and N⁶-benzyladenine (BA), embryogenesis was induced in the second step of culture when BA was removed from the medium and the concentration of 2,4-D was decreased to 2.25 μM.     

Somatic embryogenesis and plant regeneration from leaf tissue of jojoba

A protocol was developed for the induction, maturation and germination of somatic embryos from leaf tissue of jojoba [Simmondsia chinensis (Link) Schneider]. Explants were placed on their adaxial sides in Petri dishes and maintained in darkness on half-strength Murashige and Skoog basal medium (MS/2). Combinations of 2,4-dichlorophenoxyacetic acid (1.35–4.52 μM) with 6-benzylaminopurine (1.33–4.43μM) and 2 synthetic cytokinins, N-(2-chloro-4pyridyl)-N′-phenylurea (1.21–4.03μM) or (E)-6-[3-(trifluoromethyl)-but-2-enylamino] purine (1.11–3.71μM) resulted in formation of embryogenic cultures and somatic embryos. After two 30-day subcultures, embryogenic cultures were transferred onto MS/2 medium supplemented with different auxins and cytokinins. Somatic embryo maturation, germination and plantlet formation were achieved using 1-naphthaleneacetic acid (3.75μM) or indole-3-butyric acid (3.44μM) in combination with BA (0.44 or 1.33μM) or F3iP (0.37 or 1.11μM). Histology confirmed each stage of development. This revised version was published online in June 2006 with corrections to the Cover Date.     

Somatic embryogenesis and plant regeneration from embryonic tissues ofCamellia japonica L.

Somatic embryogenesis and plantlet regeneration were achieved from immature and mature zygoticCamellia japonica embryos cultured on Murashige & Skoog's mineral medium without growth regulators or with various combinations of IBA and BAR The dependence of embryogenesis rates on growth regulator levels was not clear, though high concentrations such as 4 mg 1^-1BAP plus 2 mg 1^-1IBA were definitely inhibitory. BAP at 1 or 2 mg 1^-1 did appear to determine the formation of bud-like embryos. By far the most responsive initial explants were immature embryonic axes collected in September, 94% of which produced somatic embryos as against only 20% for embryonic axes from mature seeds collected in October. Cotyledon explants were also embryogenic. Somatic embryos differentiating directly on the hypocotyl of the embryonic axes or the surface of cotyledons passed through typical stages of embryogenesis. Indirect somatic embryogenesis via callus was also evident. Embryogenic potential was maintained by secondary embryogenesis through the successive generations of embryos.     

Somatic embryogenesis and plant regeneration from floral explants of cacao (Theobroma cacao L.) using thidiazuron

Summary A procedure for the regeneration of cacao (Theobroma cacao) plants from staminode explants via somatic embryogenesis was developed. Rapidly growing calli were induced by culturing staminode explants on a DKW salts-based primary callus growth (PCG) medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and thidiazuron (TDZ) at various concentrations. Calli were subcultured onto a WPM salts-based secondary callus growth medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and 1.4 nM kinetin. Somatic embryos were formed from embryogenic calli following transfer to a hormone-free DKW salts-based embryo development medium containing sucrose. The concentration of TDZ used in PCG medium significantly affected the rate of callus growth, the frequency of embryogenesis, and the number of somatic embryos produced from each responsive explant. A TDZ concentration of 22.7 nM was found to be the optimal concentration for effective induction of somatic embryos from various cacao genotypes. Using this procedure, we recovered somatic embryos from all 19 tested cacao genotypes, representing three major genetic group types. However, among these genotypes, a wide range of variation was observed in both the frequency of embryogenesis, which ranged from 1 to 100%, and the average number of somatic embryos produced from each responsive explant, which ranged from 2 to 46. Two types of somatic embryos were identified on the basis of their visual appearance and growth behavior. A large number of cacao plants have been regenerated from somatic embryos and established in soil in a greenhouse. Plants showed morphological and growth characteristics similar to those of seed-derived plants. The described procedure may allow for the practical use of somatic embryogenesis for clonal propagation of elite cacao clones and other applications that require the production of a large number of plants from limited source materials.     

Somatic embryogenesis and plant regeneration in Piper aduncum L

In Vitro Cellular & Developmental Biology - Plant - An efficient protocol is reported for in vitro plant regeneration through somatic embryogenesis in Piper aduncum, a Brazilian Amazon species...     

Somatic embryogenesis and plant regeneration from root segments of Psoralea corylifolia L., an endangered medicinally important plant

Summary An efficient plant regeneration protocol has been developed from root explants of Psoralea corylifolia L., an endangered medicinally important herbaceous plant species belonging to the family Fabaceae. Nodular embryogenic callus was initiated from young root segments cultured on Murashige and Skoog (MS) medium (1962) supplemented with α-naphthaleneacetic acid (NAA; 2.68–13.42 μM) or 2,4-dichlorophenoxyacetic acid (2.4-D; 2.25–11.25 μM) in combination with 6-benzylaminopurine (BA: 2.2. μM). thiamine HCl (2.9 μM), L-glutamine (342.23 μM) and sucrose (3.0% w/v). The highest frequency (95.2%) of embryogenic calluses was obtained on MS medium supplemented with the growth regulators NAA (10.74 μM) and BA (2.2 μM). Development and maturation of somatic embryos was achieved after transfer of embryogenic calluses to MS medium supplemented with 1.34 μM NAA or 1.12 μM 2,4-D and 4.4–13.2 μM BA. The maximum number (13.8±1.34) of cotyledonary stage somatic embryos was obtained on MS medium containing 1.34 μM NAA and 13.2 μM BA. Germination of somatic embryos occurred on MS medium without any growth regulators and also on MS medium enriched with BA (1.1–8.8 μM), although the maximum germination frequency (76.1%) was obtained on 4.4 μM BA plus 1.45 μM gibberellic acid (GA₃). Plant regeneration without complete somatic embryo maturation was also achieved by transferring clumps of nodular embryogenic calluses onto MSO medium or MS medium supplemented with NAA (1.34 μM) and BA (2.2–8.8 μM). The highest frequency of plant regeneration (93.3%) and mean number of plantlets (15.4±0.88) were obtained on MS medium containing 1.34 μM NAA and 4.4 μM BA. Regenerated plants with well-developed root systems were transferred to pots where they grew vigorously, attained maturity and produced fertile seeds.     

Somatic embryogenesis and plant regeneration inCoronilla varia L. (crownvetch) long-term tissue cultures

Spontaneous recovery of regeneration abilities was observed in a long-term (about two-year-old) crownvetch (Coronilla varia L.) tissue culture permanently grown on MS medium containing 1 mg 1^-1 IAA. Somatic embryos and later complete plants differentiated from initially regenerating roots. The formation and development of embryos was accompanied by a 10- to 20-fold increase in the content of cardioactive glycosides hyrcanoside and deglucohyrcanoside in the culture biomass. The effect of auxins (IAA, NAA, 2,4-D) and cytokinins (6-BAP) on calogenesis and somatic embryogenesis was examined; further development of somatic embryos was enhanced by light. Primary explants which were newly isolated from sterile R₁ plantlets showed differential, organ-specific ability of somatic embryogenesis which was highest in root cuttings. Regenerated plants were transferred to field culture; two-year-old cultures of regenerated plants showed in most cases phenotypic deviations from the original material, especially dwarfism.     

番木瓜体细胞胚胎发育与植株再生

以番木瓜(穗中红-48)漏斗型体细胞胚胎为材料,探讨体细胞胚胎发育及植株再生的适宜条件。研究结果表明,附加2%椰乳、0.1mg/L ABA及40g/L蔗糖的MS固体培养基较适合番木瓜漏斗型胚状体的发育及成熟。充分成熟的子叶型胚状体在大量元素减半、蔗糖含量30g/L的MS培养基上,配合15001x光照可再生健康小植株;再生率为78%。     

Plant regeneration from encapsulated somatic embryos of Carica papaya L.

Carica papaya L. (papaya) single somatic embryos (2.0 mm diameter) produced in a high-frequency liquid production system were encapsulated in two different synthetic encapsulation compounds. The frequency of regeneration from encapsulated embryos was significantly affected by (1) the concentration of sodium alginate, (2) the presence or absence of nutrient salts in the capsule, and (3) the duration of exposure to calcium chloride. A 2.5% sodium alginate concentration in a half-strength MS salts base resulted in significantly higher germination frequencies than other treatments. A relatively short (10 min) exposure to CaCl₂ provided uniform encapsulation of embryos and the highest frequencies of successful germination (77.5%). Germinated artificial seeds produced normal plantlets. Received: 12 March 1997 / Revision recieved: 24 June 1997 / Accepted: 18 July 1997     

Somatic embryogenesis and plant regeneration from leaf callus of Ocimum basilicum L

A effective protocol for complete plant regeneration via somatic embryogenesis has been developed for Ocimum basilicum L. Callus was initiated from leaf explant of young plant on supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) 1.0 mg l(-1), 3% sucrose and 0.9% agar. The calli showed differentiation of globular structure embryos when transferred to MS medium containing 2,4-D 0.5 mg l(-1) and BAP 1.0 mg l(-1). The maximum globular structure embryos were further enlarged and produced somatic embryos in MS basal medium supplemented with BAP 1.0 mg l(-1)+NAA 1.0 mg l(-1) + KN 0.5 mg l(-1). Continued formation of globular embryo and germination of embryos occurred in this medium. Complete plantlets were transferred onto specially made plastic cup containing soilrite followed by their transfer to the garden soil. Survival rate of the plantlets under ex vitro condition was 80%.     

Somatic embryogenesis and plant regeneration from cotyledons of walnut,Juglans regia L.

Immature cotyledons of open-pollinated seeds from five walnut (Juglans regia L.) cultivars were excised from fruits at 6–11 weeks after full pistillate bloom and grown on a sequence of media to induce somatic embryogenesis. Globular, heart, cotyledonary and complete somatic embryos were obtained. Embryogenic cultures were maintained for more than a year by repetitive embryogenesis in which the roots, cotyledons and hypocotyls of somatic embryos formed additional adventive somatic embryos. Mature somatic embryos required a cold treatment of 8–10 weeks at 2–4°C to overcome apical dormancy. Selected plantlets derived from these somatic embryos were grown to young plants in soil. In addition, somatic embryogenesis was induced in J. hindsii (Jeps.), Jeps., and in Pterocarya sp., another member of the Juglandaceae.     

Somatic embryogenesis and plant regeneration from cell suspension cultures of Cucumis sativus L.

A procedure for the regeneration of whole cucumber plants (Cucumis sativus L. cv. Poinsett 76) by embryogenesis from cell suspension cultures is described. Embryogenic callus was initiated from the primary leaves of 14–17 day old plants. Suspension cultures of embryogenic cells were grown in liquid Murashige and Skoog basal medium containing 5 uM 2,4,5-trichlorophenoxyacetic acid and 4 uM 6-benzylaminopurine. Suspension cultures were composed of a population of cells that were densely cytoplasmic and potentially embryogenic. Differentiation of embryos was enhanced by washing the suspension culture cells with MS basal medium containing 0.5% activated charcoal and twice with MS basal medium followed by liquid shake cultures in MS basal medium. Sixty to 70 percent of the embryos prewashed with activated charcoal germinated into plantlets with normal morphology. Embryos obtained from suspension cultured cells without prewashing with activated charcoal organized into plantlets with abnormal primary leaves. Morphologically normal plantlets were obtained by excising the shoot tips and transferring them to fresh medium.Abbreviation BAP 6-benzylaminopurine - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - MS Murashige and Skoog     

Somatic embryogenesis and plant regeneration in tissue cultures of radish (Raphanus sativus L.)

Hypocotyl segments of 2- to 3-week-old radish (Raphanus sativus L. cv. F₁ Handsome Fall) seedlings produced yellowish compact calli when cultured on Murashige and Skoog's (MS) medium supplemented with 1 mgl^-1 2,4-dichlorophenoxyacetic acid (2,4-D). Upon transfer onto medium containing 6-benzyladenine and -naphthaleneacetic acid, up to 5.3% of the calli gave rise to a few somatic embryos. When subcultured for 3 to 6 months, 7% of the yellowish, compact calli produced white, compact calli which formed numerous embryos. These calli maintained their embryogenic capacity for over 18 months. When cultured on medium containing 0.1 to 3 mgl^-1 2,4-D, up to 90% of longitudinally sliced somatic embryo halves produced calli with numerous secondary embryos. Embryos were transferred onto medium containing 0.1 mgl^-1 2,4-D and 1 mgl^-1 abscisic acid where they developed into the cotyledonary stage. Upon transfer onto half-strength MS basal medium, approximately 90% of the embryos developed into plantlets. These plantlets were successfully transplanted in potting soil and after cold treatment they were grown to maturity in a phytotron.Abbreviation 2,4-D 2,4-dichlorophenoxyacetic acid - BA 6-benzyladenine - GA₃ gibberellin A₃ - IAA indole-3-acetic acid - MS Murashige and Skoog - NAA -naphthaleneacetic acid