Somatic embryogenesis to overcome low seed viability and conserve wild banana (Ensete superbum (Roxb.) Cheesman)

The seed viability, ex vitro germination, and percentage of in vitro zygotic embryo germination were found to be very low in Ensete superbum (Roxb.) Cheesman. Only 33.33% of seeds were viable, and the ex vitro germination percentage was only 5%, while the percentage of in vitro zygotic embryo germination was 33%. Somatic embryogenesis experiments produced competent callus on Murashige and Skoog (MS) medium supplemented with 2.5 mg L⁻¹ 2,4-D and 3 mg L⁻¹ BAP from inflorescence explants. The embryogenic callus produced the maximum number of somatic embryos on MS basal medium kept in a dark chamber for 15 wk. Half-strength MS medium supplemented with 500 mg L⁻¹ glutamine was optimal for somatic embryo germination and development of plantlets. Regenerated plants had 80 to 90% survival rate. Therefore, somatic embryogenesis can be considered as an efficient method to overcome a drastic reduction in population and to achieve germplasm conservation.

     

Effects of type of explant and age,plant growth regulators and medium strength on somatic embryogenesis and plant regeneration in <Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis>

Plant regeneration was achieved through direct and indirect somatic embryogenesis in Eucalyptus camaldulensis. Callus was induced from mature zygotic embryos and from cotyledon explants collected from 10, 15, 25, and 30-day-old seedlings cultured on Murashige and Skoog (MS) basal medium supplemented with different concentrations of naphthaleneacetic acid (NAA). Maximum callus induction from mature zygotic embryos was obtained on MS basal medium containing 1 mg l⁻¹ NAA. The frequency of callus development varied based on the age of the cotyledon explants 10-day-old explants giving highest percentage on MS basal medium supplemented with 1 mg l⁻¹ NAA. Callus obtained from mature zygotic embryos gave highest frequency of somatic embryogenesis on MS basal medium containing 0.5 mg l⁻¹ benzyladenine (BA) and 0.1 mg l⁻¹ NAA. Separate age wise culture of the calli, obtained from cotyledons of different ages cultured separately, revealed high somatic embryogenic potential on callus from 10-day-old cotyledons. Direct somatic embryogenesis too was obtained from hypocotyl explants without an intervening callus phase on MS basal medium containing 0.5 mg l⁻¹ BA. The effects of abscisic acid (ABA), sucrose, and different strengths of MS medium on somatic embryo maturation and germination were also investigated. Number of mature somatic embryos increased with lower concentrations (0–1 mg l⁻¹) of ABA while no significant differences were observed at higher concentrations (2–5 mg l⁻¹) of ABA. Compared to basal medium containing lower concentrations of sucrose (1%), the MS medium supplemented with higher levels of sucrose (4%) showed significantly lower frequency of mature somatic embryos. Basal medium without any dilution gave the highest number of immature embryos. However, the number of mature embryos was high at higher medium dilutions.     

A combined pathway of somatic embryogenesis and organogenesis to regenerate radiata pine plants

This study describes for the first time in Pinus genus a plant regeneration system via a combined pathway of somatic embryogenesis and organogenesis from immature seeds of radiata pine. Somatic embryos were obtained from embryogenic line 2162 of Pinus radiata D. Don on EDM basal medium containing 60 μM ABA and 6% sucrose. The explants used for organogenesis experiments were either freshly collected somatic embryos or somatic embryos germinated for 1 week. Germination medium was half-strength LP medium, supplemented with 0.2% activated charcoal. Different induction periods and BA concentrations were assayed for shoot induction. After induction treatments, explants were elongated on the same medium used for germination stage. Rooting medium was quarter-strength LP medium supplemented with three different auxin treatments: 1.5 mg L⁻¹ 1-naphthalene acetic acid (NAA), 1.5 mg L⁻¹ indole-3-butyric acid (IBA) and 1 mg L⁻¹ IBA with 0.5 mg L⁻¹ NAA (MIX). The effect of the photon flux (120 mmol m⁻² s⁻¹ and darkness) in the first week of the explants in the rooting media was also tested. This methodology could offer an alternative to overcome some problems associated with somatic embryogenesis such as the seasonality of embryogenic tissue (ET) initiation or a low embryo production from the ET, a particularly important issue in the case of genetically transformed ETs.     

Somatic embryogenesis and plant regeneration in two wild cotton species belong to G genome

The present work describes the plant regeneration via somatic embryogenesis in two wild cotton species belonging to G genome: Gossypium nelsonii Fryx and Gossypium australe F Muell. The role of plant hormones and carbohydrates was also evaluated for somatic embryogenesis and somatic embryo development. Normal plants were obtained from G. nelsonii Fryx; abnormal plants and somatic embryos were obtained from G. australe F Muell. The best medium for callus induction for these G genome wild cotton species was MSB₅ supplemented with 0.1 mg L⁻¹ KT and 0.1 mg L⁻¹ 2,4-D. For embryogenic callus proliferation, the best medium used was MSB₅ supplemented with 0.2 mg L⁻¹ KT and 0.5 mg L⁻¹ IBA. The medium MSB₅ supplemented with 0.15 mg L⁻¹ KT and 0.5 mg L⁻¹ NAA was used successfully for root initiation and plant growth. In addition, adding CuSO₄ and AgNO₃ in the callus-inducing and proliferation medium resulted in a number of somatic embryos. Glucose and maltose, the carbon sources in somatic culture, were used for callus induction, but maltose worked even better than glucose for proliferation of embryogenic callus and development of somatic embryos.     

Callus induction and high-efficiency plant regeneration via somatic embryogenesis in <Emphasis Type="Italic">Papaver nudicaule</Emphasis> L., an ornamental medicinal plant

We describe culture conditions for a high-efficiency in vitro regeneration system of Papaver nudicaule through somatic embryogenesis and secondary somatic embryogenesis. The embryogenic callus induction rate was highest when petiole explants were cultured on Murashige and Skoog (MS) medium containing 1.0 mg l⁻¹ α-naphthaleneacetic acid (NAA) and 0.1 mg l⁻¹ 6-benzyladenine (BA) (36.7%). When transferred to plant growth regulator (PGR)-free medium, 430 somatic embryos formed asynchronously from 90 mg of embryogenic callus in each 100-ml flask. Early-stage somatic embryos were transferred to MS medium containing 1.0 mg l⁻¹ BA and 1.0 mg l⁻¹ NAA to germinate at high frequency (97.6%). One-third-strength MS medium with 1.0% sucrose and 1.0 mg l⁻¹ GA₃ had the highest frequency of plantlet conversion from somatic embryos (91.2%). Over 90% of regenerated plantlets were successfully acclimated in the greenhouse. Secondary somatic embryos were frequently induced directly when the excised hypocotyls of the primary somatic embryos were cultured on MS medium without PGRs. Sucrose concentration significantly affected the induction of secondary embryos. The highest induction rate (89.5) and number of secondary somatic embryos per explant (9.3) were obtained by 1% sucrose. Most secondary embryos (87.2–94.3%) developed into the cotyledonary stage on induction medium. All cotyledonary secondary embryos were converted into plantlets both in liquid and on semisolid 1/3-strength MS medium with 1.0% sucrose.     

花楸合子胚诱导体细胞胚胎发生研究

分别以完整成熟胚、切去一个子叶的成熟胚和切下的子叶为外植体,以MS为基本诱导培养基、1/2MS为基本分化培养基,进行了花楸体细胞胚胎发生研究。结果表明:以完整合子胚作为外植体的体胚诱导率最高,为100%,最佳植物生长调节剂组合为5 mg.L-1NAA+2 mg.L-16-BA;NAA和6-BA浓度及二者的交互作用对愈伤组织和体胚诱导率的影响极显著;光照配合延长继代间隔时间有利于体胚发生。实体观察结果表明,花楸体胚发生方式有直接发生和间接发生两种;体胚发育经历了球形期、心形期、鱼雷形期和子叶期。组织学观察结果表明,体胚具有两极性,子叶期体胚结构完整。     

Autopolyploid induction via somatic embryogenesis in Lilium distichum Nakai and Lilium cernuum Komar

New ornamental varieties of high quality can be created via artificial polyploid induction. In the present study, the first system of polyploid induction with somatic embryogenesis of Lilium distichum Nakai and Lilium cernuum Komar. was developed. Somatic embryos were cultured on MS with 0.41 μmol L^?1 picloram and 1.07 μmol L^?1 NAA by scales (5 mm²). After 40 days, somatic embryos were transferred to MS with 2.21 μmol L^?1 BA for somatic embryogenesis. As determined from observations of paraffin sections, embryonic cells of L. distichum originated from outer cells at first, and somatic embryogenesis occurred through an indirect pathway. In L. cernuum, embryonic cells originated from inner cells at first, and somatic embryogenesis occurred through a direct pathway. Polyploids were successfully formed from somatic embryos and scales by the soaking and mixed culture methods with different colchicine concentrations (0.01%, 0.05%, and 0.1%; v/v) and durations (24, 48, and 72 h). The polyploid induction rate reached 57.14% and 46.15% with 0.05% colchicine treatment in L. distichum (48 h) and L. cernuum (24 h), respectively. Tetraploids (28.57% and 23.08%) and aneuploids without chimeras among the obtained polyploid plantlets were identified by chromosome counts of root-tip tissue squashes in L. distichum and L. cernuum. Tetraploid plantlets of L. distichum exhibited broader leaves, longer guard cells, larger stomata and higher stomatal conductance than diploid plantlets. Tetraploid plantlets of L. cernuum showed 1.76?×?higher chlorophyll content, significantly more leaves, longer guard cells, larger stomata and lower stomatal conductance than diploid plantlets.

     

First evidence of somatic embryogenesis from needles of 1-year-old Picea abies plants

Summary Somatic embryogenesis was obtained from hypocotyls and cotyledons of one month old plantlets of Picea abies. Embryogenic yield was higher with expiants from somatic embryo-derived plantlets (80 %) than with plantlets issued from zygotic embryos (10 %). This report also describes production of embryogenic calli from needles of 14 month old somatic embryo-derived plants cultivated in greenhouse. The influence of the physiological status and genotype of the mother plant on somatic embryogenic potential is discussed.Abbreviations ABA abscisic acid - (±) ABA racemic ABA - BAP 6-benzylaminopurine - CI callus inducing culture medium - NAA 1-naphtaleneacetic acid     

Plant regeneration through somatic embryogenesis from callus induced on immature embryos of Alstroemeria spp. L.

Summary The plant regeneration ability of callus obtained from zygotic embryos of the monocot Alstroemeria spp. was studied. The best explants for somatic embryogenesis were immature zygotic embryos in half-ovules when the endosperm was still soft and white. For 2 genotypes embryogenic callus was induced on callus induction medium with a success rate of 54%. The best callus induction period was 10 weeks. The morphology of embryogenic callus was nodular. Somatic embryos were formed after transfer of the callus to regeneration medium. These somatic embryos revealed later on the typical features of zygotic Alstroemeria embryos. The total duration of the plant regeneration protocol, from inoculation till rooted plantlets ready for transfer to the greenhouse, was 28 weeks.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog (1962) - NAA -naphthaleneacetic acid     

Agrobacterium-mediated genetic transformation of California poppy, Eschscholzia californica Cham., via somatic embryogenesis

 An efficient Agrobacterium-mediated protocol for the stable genetic transformation of Eschscholzia californica Cham. (California poppy) via somatic embryogenesis is reported. Excised cotyledons were co-cultivated with A. tumefaciens strain GV3101 carrying the pBI121 binary vector. Except for the co-cultivation medium, all formulations included 50 mg l⁻¹ paromomycin as the selective agent and 200 mg l⁻¹ timentin to eliminate the Agrobacterium. Four to five weeks after infection, paromomycin-resistant calli grew on 80% of explants in the presence of 2.0 mg l⁻¹ 1-naphthaleneacetic acid (NAA) and 0.1 mg l⁻¹ 6-benzylaminopurine (BAP). Calli were cultured on somatic embryogenesis induction medium containing 1.0 mg l⁻¹ NAA and 0.5 mg l⁻¹ BAP, and somatic embryos were visible on 30% of the paromomycin-resistant calli within 3–4 weeks. Three to four weeks after the somatic embryos were transferred to phytohormone-free plant regeneration medium, 32% converted to paromomycin-resistant plants. Detection of the neomycin phosphotransferase gene and high levels of β-glucuronidase (GUS) mRNA and enzyme activity, and the cytohistochemical localization of GUS activity in all plant tissues confirmed the integrative transformation of the regenerated plants. The normal alkaloid profile of California poppy was unaffected by the transformation process; thus, the reported protocol could serve as a valuable tool to investigate the molecular and metabolic regulation of the benzophenanthridine alkaloid pathway. Received: 27 October 1999 / Revision received: 6 December 1999 / Accepted: 11 January 2000     

A rapid system for micropropagation of <Emphasis Type="Italic">Swertia chirata</Emphasis> Buch-Ham. ex Wall.: an endangered medicinal herb via direct somatic embryogenesis

An improved method of direct somatic embryogenesis (SE) was developed in Swertia chirata for the first time using leaves and roots of in vitro-grown young seedlings. In the present study, 2,4-dichlorophenoxyacetic acid (2,4-D) was assessed individually and in combination with other auxins, as well as with cytokinin for its effectiveness to induce somatic embryos. Leaf explants with abaxial side in the medium produced maximum number of somatic embryos. This system omits the callus stage and thus reduces the process of SE in S. chirata by 35–45 days. Embryos at different stages of development were observed. Maturation of heart stage embryos were observed on Murashige and Skoog (MS) medium containing 1 mg L⁻¹ 2,4-D. Upon transfer to the germination medium, they were converted to cotyledonary stage and then plantlets of 33% and 68% of them were converted to cotyledonary stage and then plantlets on MS medium supplemented with 0.05 and 0.1 mg L^-1 GA₃ respectively. The 2,4-D alone at 1.0 or 1.5 mg L⁻¹ was found to be better for embryogenic tissue initiation than 2,4-D in combination with indole-3-acetic acid or α-naphthalene acetic acid. For further embryo development, 2,4-D was combined with cytokinins such as 6-benzylaminopurine (BAP) and kinetin or plant growth regulator free medium or medium with 50% reduced concentration of the same hormone while subculturing. Mean germination and percentage of survival were maximum in the medium containing 1.0 mg L⁻¹ 2,4-D in combination with 0.1 mg L⁻¹ BAP. Regenerated plantlets were morphologically and genetically identical. This method offers a vast scope for the clonal propagation of endangered plants.     

Somatic embryogenesis and plantlet regeneration from mature zygotic embryos of Manchurian ash (Fraxinus mandshurica Rupr.)

Using mature cotyledonary explants of Fraxinus mandshurica, an efficient plant regeneration system was developed via somatic embryogenesis. More than 67 % of mature cotyledons of zygotic embryos yielded 23–159 somatic embryos (SEs) per explant when incubated on medium consisting of half-strength Murashige and Skoog (MS) salts and vitamins (MS1/2) supplemented with 8.88 μM 6-benzyladenine (BA), 26.84 μM naphthaleneacetic acid (NAA), 75 g L^?1 sucrose, and 400 mg L^?1 casein hydrolysate (CH). Approximately, 82 % of induced SEs were observed on browning cotyledonary explants. Histological studies of cotyledon explants at various stages of somatic embryogenesis revealed that the SEs originated from single epidermal cells and developed to the globular, heart, torpedo, and cotyledonary stage embryos. Secondary somatic embryos (SSEs) formed on the surface of radicle tips of the SEs. Addition of low concentrations of NAA and 200–400 mg L^?1 CH to MS1/2 medium increased SSE induction. Cotyledonary SSEs were cultured on MS1/2 medium with 10 mM abscisic acid in the presence of light to promote maturation, and >92 % of mature SSEs were able to germinate with normal shoots. After 8 weeks in culture in the presence of light on medium with one-third of the MS macroelements as well as 0.06 μM NAA, >94 % of the germinated SSEs converted into plantlets. Plantlets acclimatized successfully to ex vitro conditions and developed normal phenotypes under field conditions.     

Plant regeneration by somatic embryogenesis from cultured immature embryos of oak (Querem robur L.) and linden (Tilia cordata Mill.)

Embryogenic cultures and somatic embryos were obtained from immature zygotic embryos of oak (Quercus robur L.) cultured on a modified MS medium and WPM containing BAP (1 mg·l^–1) and GA₃ (1 mg·l^–1) or BAP and IBA. Germination and conversion of oak somatic embryos into plantlets was achieved on WPM containing a reduced concentration of cytokinin. Linden (Tilia cordata Mill.) somatic embryos developed in embryogenic tissues initiated from immature zygotic embryos cultured on a modified MS medium supplemented with 2,4-D (0.3-2.0 mg·l^–1). Germination of linden somatic embryos and plantlet formation occurred on MS medium containing a low concentration of IBA. Oak and linden plantlets produced from somatic embryos were successfully established in soil. Somatic embryos and plantlets were also regenerated from embryogenic cultures of Quercus petraea and Tilia platyphyllos.Abbreviations BAP 6-benzyIaminopurine - GA₃ gibberellic acid - IBA indole-3-butyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog (1962) - WPM woody plant medium     

Somatic embryogenesis and plant regeneration from cotyledonary explants of green gram [Vigna radiata (L.) Wilezek.]—A recalcitrant grain legume

Summary This study reports a protocol for plant regeneration from cultured explants of green gram [Vigna radiata (L.) Wilezek] via somatic embryogenesis. Somatic embryos were induced from nature cotyledons of var., TAP-7 and Pusa Baisaki when cultured on Murashige and Skoog (MS) medium fortified with different concentrations of 2,4-dichlorophenoxyacetic acid, α-naphthaleneacetic acid (NAA) and 2,4,5-trichlorophenoxyacetic acid singly or in combination with 2.22–8.88 μM N ⁶-benzylaminopurine (BAP) or 2.32–9.38 μM kinetin. The type and concentration of auxin and plant genotype influenced the frequency of somatic embryogenesis. NAA was the most effective auxin for somatic embryo induction. The well-developed, cotyledonary shaped embryos of var. TAP-7 germinated into plantlets at a frequency of 56.6% on MS medium supplemented with 1.88 μM abscisic acid and 6.66 μM BAP. Regenerated plants were transferred to soil and grown to maturity with 90% survival. The protocol described here offers a good potential for genetic improvement using gene transfer techniques and the production of synthetic seeds of V. radiata.     

Somatic embryogenesis and plant regeneration in olive (Olea europaea L.)

Leaf discs from olive (Olea europaea L.) grown in vitro and immature zygotic embryos collected at 50, 75, 90 and 105 days after full bloom were tested for their somatic embryogenic capacity. The embryos were grown in half-strength MS medium and half-strength OM medium with BAP combinated with either 2,4-D or NAA. Incubation was either in an initial dark period followed by 16h daylight or in 16h daylight throughout. Somatic embryogenesis, approx. 40%, mostly directly from the embryos, was observed only in 75-day-old embryos in medium containing low cytokinin and auxin concentrations. Differentiation was inhibited by 2,4-D whereas NAA did not. In leaf discs and younger and older zygotic embryos, only callus and root formation was observed. Somatic embryos were germinated and then potted-up to soil.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine - NAA naphtaleneacetic acid     

Somatic embryogenesis and plantlet formation from a rare and endangered tree species,Oplopanax elatus

We tested the possibility of plantlet formation via somatic embryogenesis with leaf segments and mature zygotic embryos from a rare and endangered tree species,Oplopanax elatus. To induce calli, expiants were cultured under darkness in a solid MS medium containing 3% sucrose, 1g L^-1 glutamine, and 0.3% gelrite. Treatment supplements included 2,4-D alone or in combination with thidiazuron. Generally, callus induction and growth were good from leaf expiants, whereas embryogenic calli could be induced only from zygotic embryos. These embryogenic calli were white or pale yellow and very friable. ABA and activated charcoal appeared to be important factors when inducing somatic embryos, with optimum levels being 0.1 mg L^-1 and 0.02%, respectively. Many somatic embryos showed abnormalities during their development on the germination medium, but 35% could be converted if placed on a medium containing gibberellic acid (GA₃). The germinating embryos sometimes formed secondary embryos at the lower portion of the hypocotyls. Normal or converted plantlets were acclimatized in an artificial soil mixture; their survival was about 60% after two months. This culturing system provides a feasible approach for regenerating plants, via somatic embryogenesis, from mature zygotic embryos.     

Somatic embryogenesis and plant regeneration in different organs ofEuterpe edulis mart. (Palmae): Control and structural features

Somatic embryogenesis and further plant regeneration were observed using zygotic embryos, young inflorescences and young leaves ofEuterpe edulis (Palmae) as explants. Both for the cultures of zygotic embryos and inflorescences, activated charcoal in the medium was essential for the establishment of viable cultures. Embryogenesis was induced by using a gelled basal medium with MS or Euwens salts supplemented by high 2, 4-D levels (50–100 mg L⁻¹). The embryogenic process was direct without a callus stage. For further development, cultures with globular or post-globular embryos were transferred to the basal medium with 2-iP (2.5 mg L⁻¹) and NAA (0.1 mg L⁻¹). To convert embryos to plantlets, cultures were transferred to a third medium in which sucrose and salts were reduced to the half-strenght of the basal medium, without growth regulators. In the case of liquid medium, with either 2, 4-D or NAA (10–20 mg L⁻¹). The developmental stage of each explant was critical for the induction of embryogenesis. The histological study of embryogenic cultures revealed that in the case of zygotic embryos, somatic embryos arise directly from the surface of the cotyledonar node, or from subepidermal tissues. In the inflorescences, a pro-embryogenic tissue is formed at the floral primordium region; in the leaves, the first morphogenic event is cell proliferation in the vascular parenchyma.     

Somatic embryogenesis and direct as well as indirect organogenesis in Lilium pumilum DC. Fisch., an endangered ornamental and medicinal plant

Somatic embryogenesis and organogenesis in Lilium pumilum were successfully regulated by picloram, α-naphthaleneacetic acid (NAA), and 6-benzyladenine (BA). In organogenesis, the highest shoot regeneration frequency (92.5%) was obtained directly from bulb scales on Murashige and Skoog (MS) medium containing 2.0 mg L^?1 BA and 0.2 mg L^?1 NAA, while organogenic callus (OC) formed from leaves on MS medium supplemented with 1.0 mg L^?1 BA and 0.5 mg L^?1 NAA. Following subculture, 76.7% of OC regenerated shoots. In somatic embryogenesis, the combination of picloram and NAA increased the amount of embryogenic callus (EC) that formed with a maximum on 90.7% of all explants which formed 11 somatic embryos (SEs) per explant. Differences between EC and OC in cellular morphology and cell differentiation fate were easily observed. SEs initially formed via an exogenous or an endogenous origin. The appearance of a protoderm in heart-shaped SE and the bipolar shoot–root development in oval-shaped SE indicated true somatic embryogenesis. This protocol provides a new and detailed regulation and histological examination of regeneration pattern in L. pumilum.     

New approaches to improve the efficiency of somatic embryogenesis in oil palm (Elaeis guineensis Jacq.) from mature zygotic embryos

We developed an efficient and simple system for inducing somatic embryogenesis and regenerating plantlets from mature zygotic embryos of oil palm. Embryogenic calli were induced from mature zygotic embryos of oil palm on modified Murashige and Skoog medium with 2,4-dichlorophenoxyacetic acid or picloram, alone or in combination with activated charcoal. The greatest frequency of embryogenic callus induction (97.5%) was obtained by culturing mature zygotic embryos on callus induction medium with 450 μM picloram and 2.5 g?L^?1 activated charcoal. Embryogenic calli proliferated on a medium with a reduced concentration of picloram. Embryogenic calli were then subcultured on a medium supplemented with 12.3 μM 2-isopentenyladenine and 0.54 μM naphthaleneacetic acid, with subcultures at 4-wk intervals. Somatic embryos were regenerated on a medium with Murashige and Skoog macro- and micronutrients at half-strength concentrations supplemented with 20 g?L^?1 sucrose, 2.5 g?L^?1 activated charcoal, and 2.5 g?L^?1 Phytagel. Detailed histological analysis revealed that somatic embryogenesis followed an indirect pathway. Primary calli were observed after 4–6 wk of culture and progressed to embryogenic calli at 12 wk. Embryogenic cells exhibited dense protoplasm, a high nucleoplasmic ratio, and small starch grains. Proembryos, which seemed to have a multicellular origin, formed after 16–20 wk of culture and successive cell divisions. Differentiated somatic embryos had a haustorium, a plumule, and the first and second foliar sheaths. In differentiated embryos, the radicular protrusion was not apparent because it generally does not appear until after the first true leaves emerge.     

Direct somatic embryogenesis and plant regeneration from mature sugarbeet (Beta vulgaris L.) zygotic cotyledons

An in vitro protocol has been developed for direct somatic embryogenesis of zygotic cotyledons from mature sugarbeet (Beta vulgaris L.) embryos. Explants were sequentially cultured on modified Murashige and Skoog (MS) medium supplemented with different combinations of 2,4-D, NAA, BAP and TIBA. Somatic embryogenesis was induced within 4 weeks of culture on embryogenesis induction medium which contained MS medium supplemented with BAP and TIBA. Proliferation of somatic embryos was observed on embryo proliferation medium, which contained MS medium supplemented with BAP and NAA within 4 weeks of culture. Plants were regenerated on hormone free half; strength MS medium containing a low sucrose concentration. With some sugarbeet lines, high frequencies of plant regeneration in excess of 90percnt; were observed. The incorporation of TIBA in the media was essential for successful regeneration.