High frequency of plant regeneration from hypocotyl explants of Brassica carinata A. Br.

An efficient tissue culture system for high frequency of plant regeneration from hypocotyl explants of Brassica carinata was developed via manipulation of culture medium and selection of explants. Explants grown on medium containing combinations of 2 mg l^-1 BA and 0.01 mg l^-1 NAA or 4 mg l^-1 kinetin and 0.01 mg l^-1 2,4-D regenerated shoots at 100% frequency. High frequency shoot regeneration occurred only from explants originating from 6 to 7-day-old but not younger or older seedlings. Explants showed higher regeneration capacity at the distal end than the proximal end, and the upper segment was more regenerative than the lower segment of hypocotyl. Regenerants were rooted on half-strength growth regulator-free medium, acclimatized and developed into normal, fertile plants.Abbreviations BA benzyladenine - 2-4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - MS Murashige & Skoog     

Callus induction and high-frequency plant regeneration from hypocotyl and cotyledon explants of Arctium lappa L.

Summary This study describes a protocol for plant regeneration from cultured seedling explants of Arctium lappa. Hypocotyls and cotyledons of A. lappa were induced to form callus by culturing on Murashige and Skoog (MS) medium supplemented with 2.0mg l^−1 2,4-dichlorophenoxyacetic acid and 0.5–2.0 mg l^−1 benzyladenine (BA). Formation of adventitious buds could be induced from calluses or explants directly by culturing on MS medium containing 1.0–2.0 mg l^−1 α-naphthaleneacetic acid (NAA) and 0.5–2.0 mg l^−1 BA. These regenerated shoots were rooted on MS medium with 1.0 mg l^−1 indole-3-butyric acid or indole-3-acetic acid in combination with 1.0 mgl^−1 NAA. The regenerated plants acclimatized in soil were normal morphologically and in growth characters. They flowered and set seeds in the following year after acclimatization.     

High frequency somatic embryogenesis and plant regeneration from papaya hypocotyl callus

High frequency somatic embryogenesis in papaya (Carica papaya L.) tissue cultures was achieved by culturing hypocotyl sections from ten-day-old seedlings on half-strength Murashige and Skoog salts (MS) medium containing modified MS vitamins, 2.3 to 112.5 M 2,4-dichlorophenoxyacetic acid (2,4-d), 400 mg l^-1 glutamine, and 6% sucrose. Four hermaphroditic Hawaiian cultivars produced embryogenic calluses after ten to 14 weeks of culture at 27°C in the dark. Efficiency in embryogenic response of genotypes differed, Kapoho > Sunset > Sunrise > Waimanalo. The frequency of embryogenesis in induction medium containing 4.5 M 2,4-d was lowest with 3% sucrose and highest with 7% sucrose. Somatic embryos developed directly from embryogenic calluses on induction medium, or, more often, they differentiated from calluses subcultured on a medium devoid of growth regulators. Between 50 and 500 embryos were produced from each 2-mm hypocotyl section after at least two months on induction medium and two months on maturation medium. Embryos subsequently developed into normal-looking plants on MS medium. Shoot cuttings from germinated embryos and micropropagated plants were rooted with 5.0 M indole-3-butyric acid (IBA), grown in the greenhouse, and transferred to the field.Journal Series no. 3732 of the Hawaii Institute of Tropical Agriculture and Human Resourees     

In vitro plantlet regeneration from cotyledon, hypocotyl and root explants of hybrid seed geranium

In vitro plantlet regeneration systems for the seed geranium (Pelargonium x hortorum Bailey) using cotyledon, hypocotyl and root explants were optimized by studying the influence of seedling age, growth regulators and excision orientation on organogenesis. Indole-3-acetic acid combined with zeatin yielded the highest rate of shoot production on cotyledon explants (0.2–2 shoots per explant). More shoots were produced on explants cut from the most basal region of cotyledons from 2 to 4-day-old seedlings than from older seedlings or more distal cut sites. Hypocotyl explants produced the highest number of shoots, up to 40 shoots per explant, on indole-3-acetic acid (2.8–5.6 mM) + zeatin (4.6 mM) or thidiazuron (4.5 mM). Maximum shoot formation (0.3–1.4 shoots per explant) on root explants occurred when they were cultured on medium containing zeatin. Regenerated shoots rooted best on a basal medium containing no growth regulators. There were substantial differences among cultivars in shoot formation from each of the explant systems.Abbreviations BA 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - NAA naphthaleneacetic acid - TDZ thidiazuron     

In vitro plant regeneration from cotyledon explants of Swainsona salsula Taubert

An effective protocol has been developed for plant regeneration from cotyledon explants of Swainsona salsula Taubert (Saline swainsona), a medicinal and agronomic shrub. Adventitious shoots were obtained from 83.2% of cotyledon explants from 3-day seedlings cultured on Murashige and Skoog (MS) medium containing 2.0 mg l⁻¹ thidiazuron (TDZ), with an average of 9.3 shoots per explant. Individual elongated shoots were rooted on half strength MS medium supplemented with 2.0 mg l⁻¹ indole-3-butyric acid (IBA), with 59.3% success. Regenerated plants with well developed shoots and roots were successfully transferred to soil, without detectable variants. Histological observation revealed that shoots developed from cotyledon explants via organogenesis, with little callus. This revised version was published online in June 2006 with corrections to the Cover Date.     

In vitro regeneration of sesame (Sesamum indicum L.) from seedling cotyledon and hypocotyl explants

The goal of this study was to develop an efficient regeneration protocol to be used for genetic transformation of sesame. Published regeneration methods using benzyladenine (BA) and 1-naphthalene acetic acid (NAA) were unsuccessful for the cultivars used herein. Experiments were carried out using cotyledon and hypocotyl explants from the cultivar Mtwara-2. Later the optimised culture conditions were used to investigate the regeneration response of different genotypes. There was significant interaction between hormone treatments and macronutrients for shoot and root regeneration. Results also showed that shoot regeneration was significantly influenced by explant type. Shoots were only obtained from cotyledons whereas both cotyledons and hypocotyls could produce roots. Modified Murashige and Skoog (MS) medium with N6 macronutrients resulted in twice the shoot regeneration frequency obtained with ½MS macronutrients in the presence of thidiazuron (TDZ). The shoot regeneration frequency was significantly reduced when BA was used in place of TDZ. On shoot regeneration medium containing BA and NAA, only roots were formed. Replacing NAA with indole-3-acetic acid (IAA) greatly improved the regeneration of shoots. The optimum growth regulator combination for shoot regeneration was 20 μM TDZ together with 2.5 μM IAA, which gave a frequency of 63% and 4.4 shoots per regenerating explant for the best cultivar Ex-El. Genotypic differences were significant both for the number of explants regenerating shoots and the number of shoots produced per regenerating explant.     

High frequency plant regeneration from thin cell layer explants of Brassica napus

Explants composed of the epidermis and 4–9 layers of subepidermal cells were excised from internodes of Brassica napus L. ssp. oleifera cv. Westar and cultured on modified Murashige and Skoog (MS) medium. The three or four terminal internodes excised from plants at an early stage (before any flower buds had opened) were shown to be the best explant source. Both cytokinin and auxin were required for induction of shoot organogenesis. Of six auxins tested, only naphthaleneacetic acid (NAA) was effective in shoot bud initiation. All four cytokinins tested (when associated with 0.5 mgl^-1 NAA) promoted organogenesis, but at differing frequencies. The highest shoot induction frequency was obtained at 10–15 mgl^-1 benzyladenine (BA). The organogenic response was strongly affected by the nitrogen content of the medium. The best response was observed when NO₃ ^- was the sole nitrogen source (supplied as KNO₃) in the range 30–90 mM. Sucrose and glucose were equally supportive in shoot regeneration with the optimal levels at 0.12 M and 0.15 M, respectively. Shoots were rooted on medium free of growth regulators and mature plants were grown in the greenhouse. Plants were also recovered from leafy structures which differed morphologically and histologically from shoot buds.     

Organogenic regeneration of soybean from hypocotyl explants

Summary Thirteen soybean genotypes representing maturity groups IV−VI were compared for organogenic responses on three media cultured under two lighting conditions with hypocotyl sections excised from 7-d-old seedlings. All soybean lines responsed by producing adventitious shoots on the acropetal end of the hypocotyl explants, confirming genotype-independence of shoot initiation. Media containing 6-benzyladenine (BA; 5.0–10 μM) induced the greatest numbers of shoots. Histological studies confirmed the adventitious nature of arising shoots by indicative formation of meristematic zones and shoot primordia from parenchymatous tissues of central pith and plumular trace regions of the hypocotyl. Incompletely excised cotyledonary buds also contributed to shoot initiation. Degrees of responses were media-dependent and varied with regard to genotype. Centennial, Epps, and Lyon gave the greatest individual responses. Between cultivars (across all treatments), the regeneration potential (percentage of explants producing meristem-like structures or shoot primordia) 4 wk after initiation ranged from 47 to 75%. Four wk later, regenerative ability (number of shoots produced per responding explant) and regeneration efficiency (number of shoots produced per explant plated) yielded 1.4–7.1 and 1.0–5.0 shoots, respectively. The optimized protocol included initiation on a medium containing 5.0 μM BA for 4 wk, then transfer onto a shoot elongation medium (0.36 μM BA) for 4 wk. For 11 genotypes tested, 66–100% of excised shoots produced roots after 4 wk on media containing 12.5–29.2 μM indole-3-butyric acid. Of 109 regenerants transplanted to soil, 94% survived and no sterility has been observed on those mature enough to flower.     

Direct shoot formation and plant regeneration from cotyledon explants of rapid-cycling Brassica rapa

Summary An in vitro culture system for direct shoot regeneration from cotyledon explants of rapid-cycling Brassica rapa was developed. Cotyledons from 3-d-old seedlings, when cultured on Murashige and Skoog (MS) medium supplemented with 20 μM N⁶-benzyladenine (BA) and 2 μM α-naphthaleneacetic acid (NAA), regenerated shoots directly at a frequency of 20%. The addition of 2 μM aminoethoxyvinylglycine (AVG) to this medium increased shoot regeneration to 33%, but silver nitrate drastically inhibited shoot regeneration. Shoot regeneration occurred directly, at the petiolar cut ends of cotyledonary explants, between 10 to 17 d in culture. The highest percentage of regeneration (33%) was obtained from 3-d-old seedlings. NAA was the most effective auxin for root induction and development, with 49% of shoots producing roots after 2 wk on medium containing 1.0 μM NAA. Regenerated plantlets were grown to maturity in pots containing peat moss and vermiculite (1:1). These plants were morphologically normal and fertile. With this protocol, over 100 independently derived, flowering R₀ plants were obtained from 40 regenerating cotyledonary explants within 40 d after culture initiation.     

In vitro plant regeneration from cotyledon and hypocotyl segments in two bell pepper cultivars

In vitro plant regeneration has been obtained from Capsicum annuum cvs. Pico and Piquillo. Shootbuds were induced from hypocotyl and cotyledon segments after 15–20 days of culture on MS basal medium supplemented with IAA and BAP or Zeatin. Shoot-buds grew into rosettes that rooted in MS plus NAA (0.1 mg/l) and IBA (0.05 mg/l) after 15 days. The small plantlets were successfully transferred to pots with a mixture of peat and perlite and maintained under greenhouse conditions. Elongation took place when the plantlets were growing in the greenhouse.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - Kn Kinetin - MS Murashige and Skoog (1962) - NAA alpha-naphthalenacetic acid - Z Zeatin     

High frequency plant regeneration from stem explants of Brassica alboglabra Bailey in vitro

Culture conditions for shoot regeneration and proliferation, and rooting of Brassica alboglabra Bailey were optimized by a judicious selection of explants and manipulation of hormonal combinations in the culture medium. Both half and whole stem explants were more regenerative than cotyledons and hypocotyls. The highest shoot regeneration frequency (100%) accompanied by high number of shoots was obtained using half stem explants grown on Murashige & Skoog [14] medium supplemented with 2 mgl^-1 BA in combination with 1 mgl^-1 NAA, or 4 mgl^-1 2iP with 0.5 mgl^-1 NAA. For shoot proliferation, 4 mgl^-1 kinetin was most effective. The presence of auxin reduced shoot proliferation significantly. Maximum rooting (100%) of shoot cuttings was obtained either in the absence or in the presence of 0.5 mgl^-1 NAA, or IBA or IAA ranging from 0.1 to 8 mgl^-1.     

In vitro plant regeneration from leaf and cotyledon explants of Cucumis melo L.

Five different genotypes from in vitro as well as greenhouse grown melon plants were shown to be highly responsive for in vitro shoot formation from leaf explants when placed on basic MS medium supplemented with 1 mg/l 6-benzylaminopurine. In addition, a very suitable regeneration system was obtained when cotyledon pieces of mature seeds were incubated on the same culture medium. In this case, the first shoots already appeared after 10 days of incubation, and hundreds of shoots were formed on the cut surface 3 to 4 weeks later. Explants from mature cotyledons derived from seedlings did not lead to any shoot formation.Abbreviations MS Murashige and Skoog - IAA 3-indoleacetic acid - BA 6-benzylaminopurine     

Plantlet regeneration from cotyledon,cotyledon petiole,and hypocotyl explants via somatic embryogenesis pathway in roquette (Eruca sativa Mill)

Abstract

A high-efficiency plant regeneration protocol based on somatic embryo formation for Huining Roquette, an interesting ecotype of Eruca sativa Mill, was established for future transgenic applications. On Murashige and Skoog (MS) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D), alone or in combination with 6-benzylaminopurine (BA) or kinetin (KT), the cotyledon explants, cotyledon petioles, and hypocotyls all produced embryogenic callus (ECs) or somatic embryos (SEs) to different extents. After transferring onto hormone-free MS medium, the ECs or SEs from the different explants and media, all of them developed shoots with a frequency of 6–48%, and then produced roots with a frequency of 2–29%. As regards the probability of shoot differentiation, cotyledon explants appeared similar to hypocotyls, but superior to cotyledon petioles; 2,4-D + KT worked more effectively than 2,4-D alone and 2,4-D + BA for callus induction and shoot differentiation. The optimal hormone combinations for plant regeneration of cotyledon, cotyledon petiole, and hypocotyl explants were 1.0 mg/l 2,4-D + 0.1 mg/l KT, 0.8 mg/l 2,4-D + 0.3 mg/l BA, and 1.0 mg/l 2,4-D + 0.3 mg/l KT, respectively. MS medium with 60–80 g/l sucrose was the most effective for improving SE maturation and germination.     

Callus induction and plant regeneration from hypocotyl explants of the forage legume Astragalus adsurgens

An efficient procedure was developed for inducing callus and plant regeneration using hypocotyl segments of Astragalus adsurgens. The combinations and concentrations of different growth regulators were shown to be critical factors for both the frequency and the type of callus formation as well as for the potential of callus differentiation. Of the four morphologically distinct types of calli that were induced, a friable, yellow callus, i.e. type I, induced on MS medium supplemented with 9.0 μM 2,4-dichlorophenoxyacetic acid and 2.2 μM N⁶-benzylaminopurine (BA), and then transferred to MS medium containing 0.5 μM α-naphthaleneacetic acid and 8.9 μM BA, exhibited the maximum frequency of shoot regeneration (75%). After regenerated shoots were transferred onto half-strength MS medium without growth regulators, they rooted and complete plants were obtained. Plantlet regeneration from callus cultures required 7–8 weeks. Received: 26 February 1997 / Revision received: 28 August 1997 / Accepted: 13 September 1997     

High frequency shoot regeneration from leaf explants of muskmelon

Efficient in vitro plant regeneration systems are critical for many purposes including plant transformation. Current regeneration systems for melon (Cucumis melo L.) plants generally utilize cotyledon explants; regeneration from melon leaves has received limited attention. We investigated several factors that influence regeneration from melon leaves including: genotype growth conditions and age of the source plant, leaf age, explant orientation, gelling agent, and the addition of silver nitrate and sulfonylurea herbicide to the culture media. Critical factors that influenced regeneration were preculture conditions of the donor plants, leaf size, and the use of silver nitrate and Phytagel in the medium. The best results were obtained with 3–4 cm diam leaves excised from pot grown greenhouse or growth chamber plants cultured on MS medium with 5 M IAA, 5 M BA, 1 M ABA, 30 M silver nitrate and 2.6 g l^-1 Phytagel. Low concentratons of sulfonylurea herbicide (0.25 mg l^-1 DPX-M 6316) also enhanced regeneration. Under optimized conditions 80–100% of the explants regenerated, with 10–100 shoots per explantAbbreviations ABA abscisic acid - BA benzyladenine - IAA indole-3-acetic acid - MS Murashige and Skoog medium - NAA naphthalene acetic acid     

Efficient regeneration from hypocotyl explants in three cotton cultivars

A high frequency in vitro shoot bud differentiation and multiple shoot production protocol from hypocotyl segments of 8 to 10-d-old seedlings of cotton has been developed. Murashige and Skoog (MS) basal medium with Nitsch and Nitsch vitamins was found to be optimal in shoot regeneration. A combination of 2 mg dm⁻³ thidiazuron and 0.05 mg dm⁻³ naphthaleneacetic acid was the most effective for shoot regeneration (76 %) and an average of 10.6 shoots per responding explant. Combination of the cytokinins benzylaminopurine and kinetin induced better regeneration response than their individual treatments. Supplementation of the culture medium with ethylene inhibitor silver nitrate and activated charcoal showed beneficial effects. Optimal rooting was obtained on half-strength MS medium supplemented with 1 mg dm⁻³ indolebutyric acid and activated charcoal. Scanning electron micrographs of in vitro cultured explants revealed that shoot primordia were formed de novo.     

High frequency plantlets regeneration from seedling explants of Prosopis tamarugo

Callus cultures of Prosopis tamarugo Phil (Leguminosae, Sub family-Mimosoideae) were established from hypocotyls and cotyledons on MS medium supplemented with NAA (2.0 mg l^-1) and BAP (0.2 mg l^-1). Regeneration through various juvenile explants was obtained on hormone-free and high cytokinin containing Murashige and Skoog's medium. Multiple shoot buds formation was observed from the embryonic axis on MS medium incorporated with BAP (5.0 mg l^-1)). Elongation of shoot buds was observed on subsequent transfer to MS medium with BAP (1.0–2.5 mg l^-1) or without BAP. Explants containing apical meristem showed higher number of shoot formation at an early period. De novo shoot buds formation through callus morphogenesis was observed at the base of differentiated shoots on high cytokinin containing medium. All the manipulations of salt strength of MS, nitrogen, carbon, ascorbic acid and polyamines failed to induce organogenesis in isolated callus. In vitro produced shoots were rooted on MS medium supplemented with IBA or NAA singly or in combination.Abbreviations HC high cytokinin (BAP 5.0 mg l^-1) - BAP 6-benzyl amino purine - IBA indole-3-butyric acid - HF hormone free - NAA I-naphthalene acetic acid - MS Murashige & Skoog     

Regeneration of Echinacea purpurea: Induction of root organogenesis from hypocotyl and cotyledon explants

An in vitro propagation system was developed for Echinacea purpureaL. (purple coneflower), a medicinal plant commonly used in the treatment of colds, flu and related ailments. Root organogenesis from Echinacea purpurea hypocotyl explants was effectively induced by indolebutyric acid. Indoleacetic acid was found to be less effective than indolebutyric acid while treatments with naphthaleneacetic acid were ineffective for induction of root organogenesis. The results of this study have established a micropropagation system for Echinacea purpurea that will provide axenic plant material for further investigations into medicinally active biochemicals and the mass production of high-quality Echinacea purpurea root tissues for the commercial market. This revised version was published online in June 2006 with corrections to the Cover Date.     

High efficiency plant production of North American ginseng via somatic embryogenesis from cotyledon explants

An efficient in vitro protocol for plant production of North American ginseng has been established. The pretreatment of cotyledon explants with 1.0 M sucrose at 4 degrees C resulted in an improvement of embryo quality and, combined with a higher sucrose content (7%) in induction medium, improved the embryogenesis frequency from 40% to 75% and the number of embryos per explant from 10 to 21. The frequency of secondary embryogenesis from somatic embryo-derived tissues cultured on MS medium with 1.0 mg l(-1) 2, 4-D and 1.0 mg l(-1) NAA is up to 90%. Somatic embryos can further develop to maturity on SH medium supplemented with 1% activated charcoal and half of them can germinate. About 85% of the germinated embryos will convert into plants with well-developed taproot systems on 1/2 SH medium with 0.5% activated charcoal. The growth chamber and field establishment rates were 95.6 and 93.7%, respectively. The plants transplanted to growth chambers and field plots appear normal.     

Plant regeneration from seedling explants and cotyledon protoplasts ofGlycine argyrea tind

Summary Plants have been regenerated from nodular, green callus derived from cotyledon, petiole and leaf lamina explants ofG. argyrea, a perennial relative of the soybean (G. max). The degree of response obtained was governed primarily by the genotype used, accession G1626 proving the most responsive. Shoots were also recovered from about 6.0% of cotyledon protoplasts of this genotype. The implications of these results are discussed in relation to genetic manipulations using this species.