Percentage Of Explants Research Articles

Agrobacterium rhizogenes-mediated transformation of Brassica oleracea var. sabauda and B. oleracea var. capitata

Agrobacterium rhizogenes A4M70GUS-mediated transformation of Savoy cabbage (Brassica oleracea L. var. sabauda) and two local lines of cabbage (B. oleracea L. var. capitata) was obtained using hypocotyl and cotyledon explants. The percentage of explants which formed roots was very high in all genotypes: 92.3 % in Savoy Gg-1, 64.4 % in cabbage P22I5, and 87.2 % in P34I5. Spontaneous shoot regeneration of excised root cultures grown on the hormone-free medium occurred in all three genotypes. In cabbage lines P22I5 and P34I5 shoot regeneration was higher (9.3 and 2.6 % respectively) than in Savoy cabbage Gg-1 (1.3 %). Transgenic nature of hairy root-derived plants was evaluated by GUS histological test and PCR analysis. All the tested cabbage shoots were GUS positive whilst in a Savoy cabbage GUS expression was registered only in 55 % of tested clones. PCR analysis demonstrated the presence of the GUS gene in regenerated shoot clones and in T1 progeny.

In vitro cloning of two cumin landrace lines via shoot-tip culture

SummaryShoot-tip explants were excised from axenic and non-axenic plant cultures of two cumin (Cuminum cyminum L.) landrace lines from Assiut (ASS) and Qina (QIN), Egypt. Explants were cultured on MS (Murashige and Skoog, 1962) medium supplemented with different concentrations of benzyladenine (BA) or kinetin. The two landraces performed similarly throughout the study. Shoot-tip explants from axenic cultures were superior to those prepared from non-axenically grown plants regarding the percentage of explants that produced micro-shoots and the number of micro-shoots that proliferated. The maximum number of excisable micro-shoots was produced on medium with 1 µM BA. Up to 20 micro-shoots per explant were excised from cultures on this medium. The largest number of micro-shoots obtained on medium containing kinetin was five. Most (80–90%) micro-shoots formed roots on medium with 1 µM indole-3-butyric acid (IBA) and 2% (w/v) polyethylene glycol (PEG-6000). The survival rate ex vitro was as high as 70%. A high concentration of BA (4 µM) induced calli, retarded elongation of the micro-shoots and reduced both the number of roots formed on subsequent rooting medium, and plant survival ex vitro. This study supports the feasibility of in vitro cloning of cumin using shoot tips for germplasm collection, conservation and exchange.

Comparative adventitious shoot induction in kentucky coffeetree root and petiole explants treated with thidiazuron and benzylaminopurine

Abstract Adventitious shoot induction and elongation was compared between root and petiole explants of Kentucky coffeetree (Gymnocladus dioicus L.) explants treated with a factorial combination of benzylaminopurine (BA) and thidiazuron (TDZ). Petiole explants initiated more adventitious shoots compared to root explants. Up to 83% of petiole explants initiated shoots compared to 67% of root explants. Maximal shoot induction was approximately 12 or five shoots per responding explant for petiole and root explants, respectively. For both explant types, TDZ was more effective than BA for shoot induction. There was an interaction between BA and TDZ on shoot induction in petiole explants, with the greatest percentage of explants forming shoots and the highest number of shoots initiated on the combination of 0.5 μM TDZ plus 10 μM BA and 1.0 μM TDZ plus 5 or 10 μM BA. In contrast, increasing concentrations of BA inhibited shoot initiation in root explants with and without TDZ. While BA inhibited shoot initiation i...

Effects of antioxidants on the plant regeneration and GUS expressive frequency of peanut (Arachis hypogaea) explants by Agrobacterium tumefaciens

Our objective is to develop an Agrobacterium-based transformation system for peanut. Ascorbic acid (AA), sodium selenite (Se), DL-α-tocopherol (TOC) and glutathione (GSH) were used as antioxidants during the plant regeneration and co-cultivation with Agrobacterium tumefaciens. Percentage of explants with buds or shoots increased from 50 in control group to 88, 90, 87 and 76 in GSH, TOC, Se or AA treated groups, respectively. The percentage of GUS-positive plantlets increased from 3.9 (in control) to 14.5, 10.3, 12.4 and 3.9 in GSH, TOC, Se or AA groups, respectively. Some of the callus in AA group became brown and died 2 months later. GSH, TOC and Se not only eliminated the formation of H2O2 produced in wound tissue during preparation of leaflets and co-cultivation with Agrobacterium tumefaciens and decreased malondialdehyde (MDA) formation, but also enhanced superoxide dismutase (SOD) and catalase (CAT) activities. As a result, GSH, TOC or Se increased the frequency of plant regeneration and transformation efficiency of peanut (Arachis hypogaea L.) explants by Agrobacterium tumefaciens. AA is an unsuitable antioxidant in Murashige and Skoog (MS) medium due to the stimulation of oxidation in the presence of iron in MS medium.

In vitro regeneration of the tennessee coneflower (Echinacea tennesseensis)

Abstract Tennessee coneflower [Echinacea tennesseensis (Beadle) Small] was regenerated from flower stalks, leaf sections from flowering plants, and hypocotyls and cotyledons from seedlings. Murashige and Skoog medium (MS) supplemented with naphthaleneacetic acid (NAA) at 0.54 μM and thidiazuron (TDZ) at 22.7 μM yielded the most shoots per leaf explant. NAA and 6-benzylaminopurine concentrations for optimal shoot regeneration from leaf, flower stalk, cotyledon and hypocotyl explants in MS media were 0.54 and 24.6 μM, respectively. All explant types generated shoots; however, those derived from leaves and flower stalks produced the highest number of shoots per explant and highest percentage of explants with shoots. Explants cultured on media containing high levels of NAA (5.4–27 μM) formed calluses but no adventitious shoot. Leaf explants responded to a wider range of NAA concentrations than the other explant types but shoots generated from flower stalks grew the fastest. While all cytokinins tested increas...

Pluronic F‐68 Enhanced Shoot Regeneration in Micropropagated Citrus Rootstock and Passiflora Species

AbstractThe promotory effects have been studied of the non‐ionic surfactant, Pluronic F‐68, on bud induction/shoot regeneration in epicotyl and cotyledon explants of Citrus depressa and on shoot regeneration from leaf segments of 4–6 week‐old axenic nodal segment‐derived in vitro plants of Passiflora mollissima, P. giberti and P. edulis var. flavicarpa. For epicotyls of C. depressa, supplementation of agar‐solidified MS‐based bud induction/shoot regeneration medium with 0.5% [w/v] Pluronic F‐68 significantly (P < 0.05) increased mean fresh weight gain of cultures, percentage of explants giving shoots and number of shoots per explant. The same Pluronic concentration also enhanced the mean percentage of cotyledons exhibiting bud induction and the number of buds regenerated per cotyledon explant. Fresh weight gain was unaffected across the range of concentrations (0.001–0.5% w/v) of Pluronic F‐68 evaluated for this latter explant source. For leaf explants from axenic shoot cultures of P. mollissima, supplementation of NN‐based medium, containing 3 mg/l 6‐benzyladenine and 2.0 mg/l kinetin with 0.001–0.5% [w/v] Pluronic F‐68, significantly (P < 0.05) increased mean (± s.e.m.) biomass gain by a maximum of 2.7 ± 0.1 g fresh weight (g f.wt.) over the control. Similarly, for leaf explants of P. giberti, 0.001–0.5% [w/v] Pluronic F‐68 in MS‐based medium, containing 1.0 mg/l 6‐BAP and 0.5 mg/l kinetin significantly (P < 0.05) increased mean percentage of explants undergoing shoot regeneration. For P. edulis leaf explants, mean f.wt. gain was also significantly (P < 0.05) higher with Pluronic F‐68 at 0.001–0.5% [w/v].

MICROPROPAGATION OF TROPICAL FRUITS: BENEFICIAL EFFECTS OF NON-IONIC SURFACTANTS

The effects have been investigated of the non-ionic surfactant, Pluronic® F-68, on bud induction/shoot regeneration in epicotyl and cotyledon explants of Citrus depressa and on shoot regeneration from leaf segments of 4-6 week-old axenic plants of Passiflora edulis var. flavicarpa, P. giberti and P. mollissima. Supplementation of agar-solidified MS-based bud induction/shoot regeneration medium with 0.5% (w/v) Pluronic® F-68, significantly (P < 0.05) increased mean fresh weight gain of cultured epicotyls of C. depressa, the percentage of explants giving shoots and number of shoots regenerated per explant. This Pluronic® concentration also enhanced the mean percentage of cotyledons which developed buds and the number of buds per cotyledon. Fresh weight gain was not affected in the range 0.001 - 0.5% (w/v) of Pluronic® F-68 evaluated for cotyledon explants. Supplementation of NN-based medium with 3 mg l -1 6-benzyladenine (6-BAP), 2.0 mg l -1 kinetin and 0.001-0.5% (w/v) Pluronic® F-68, significantly (P < 0.05) increased mean (±SE) biomass gain of leaf explants of P. mollissima by a maximum of 2.7±0.1 g f.wt. over control. The same concentration range of Pluronic® F-68 in MS-based medium, containing 1.0 mg l -1 6-BAP and 0.5 mg l -1 kinetin, also significantly (P < 0.05) increased the mean fresh weight gain of P. edulis leaf explants and the mean percentage of leaf explants of P. giberti undergoing shoot regeneration.

Genetic transformation in commercial Tasmanian cultivars of opium poppy, Papaver somniferum, and movement of transgenicpollen in the field.

We report a new transformation protocol for the pharmaceutically important opium poppy, Papaver somniferum L.; the protocol allows transformation for the first time of high yielding commercial cultivars. The method involves Agrobacterium tumefaciens infection of hypocotyl explants, followed by the production of antibiotic- or herbicide-resistant embryogenic callus and the subsequent induction of somatic embryos and plants. Key elements of the improvement are the use of buffering agents to stabilise medium pH and bottom-cooling of the cultures. Transformation was verified by PCR and Southern blot hybridisation. Transcription of transgenes was confirmed by RT-PCR and product sequencing. Expression of transgenes was detected by histochemical GUS staining, phosphinothricin acetyltransferase (PAT) enzyme assays for bar and pat genes, and western analysis of transgenic sunflower seed albumin protein. Expression of various transgenes was detected in stem, leaf, seed, capsule and latex. The pat gene was demonstrated to be stably inherited to the T2 generation and to confer phosphinothricin (PPT) herbicide resistance. Most T0 plants showed normal morphology, were self-fertile and the transgenes displayed the expected Mendelian segregation. The percentage of explants producing somatic embryos that developed into plantlets able to be transplanted to soil, ranged from 6-11% in two Tasmanian cultivars.A field trial using pat transgenic plants was designed to estimate the frequency of hybridisation at various distances into buffer rows of non-transgenic poppies and to related weed species, P. somniferum spp. setigerum and P. dubium. The frequency of hybridisation to completely compatible poppy fell sharply with distance, being 2.6% at 20 cm, 2.13% at 0.5 m and falling to 0% at 2.5 and 5 m. No hybridisation could be detected to two weed species under open pollination conditions, including the compatible P. somniferum spp. setigerum, when grown as close as 20 cm, despite flowering at the same time as the transgenic plants in the presence of foraging bees.

Regeneration and transformation of the premier UK apple (Malus × pumila Mill.) cultivar Queen Cox

SummaryA number of factors were assessed for their effects on in vitro shoot proliferation and adventitious shoot regeneration. More in vitro leaves of a quality suitable for use in regeneration and transformation experiments were obtained from shoots on DKW proliferation medium compared with MS medium, and also on MS and DKW media containing phloroglucinol. Compared with MS medium, shoot proliferation was greater on MS with halved levels of NH4NO3 and KNO3. Adventitious shoots were hyperhydric on MS-based but not on DKW-based regeneration medium. More adventitious shoots regenerated on media solidified with Sigma Agargel than on media with Sigma Phytagel or Gelcarin (FMC). Viable transformed shoots were recovered on Sigma Agar or Agargel but not Phytagel. Wounding of leaf explants by stabbing with needles, and stabbing combined with scoring with a scalpel, increased the number of calli regenerating, and these methods, as well as solely scoring with a scalpel, increased the number of calli regenerating shoots compared with the control. Combined stabbing and scoring resulted in more calli producing shoots than solely scoring or stabbing. Vortexing leaf explants with silicon carbide whiskers increased the percentage of subsequently formed calli that regenerated shoots compared with the control. Transformed shoots were regenerated following co-cultivation with Agrobacterium tumefaciens EHA101 harbouring the binary vector pSCV1.6 (with selectable marker gene npt II and GUS reporter gene uid A). The number of transformed shoots as a percentage of explants varied from 0.5% to 2.2%. Molecular analysis of the four extant transformed lines confirmed integration of the transgene and indicated that in three lines there was one integration site, and in one line there were four sites of integration.

Influence of high concentrations of cytokinins on the production of somatic embryos by germinating seeds of tomato, aubergine and pepper

SummarySomatic embryos of tomato, aubergine and pepper were initiated from intact seedlings when seeds were cultured on medium containing 6-benzylaminopurine (BAP) or thidiazuron (TDZ). The percentage of explants producing somatic embryos was highest for aubergine on media containing low concentrations of BAP, i.e. 0–10 mg l–1, for tomato at 15–20 mg l–1 and for pepper at 40–80 mg l–1. Aubergine and tomato produced fewer somatic embryos per responsive seedling when cultured on medium containing TDZ, and pepper did not produce any somatic embryos on media containing 0–20 mg l–1 1 TDZ. Morphogenesis of the seedlings producing somatic embryos was similar for all the genotypes, i.e. the seedlings were dwarf, only the cotyledons expanded, development of the apical meristem and the root were suppressed and a ring-like crown of nodular tissue developed at the base of the hypocotyl from which somatic embryos were initiated. Co-cultivation of tomato and aubergine seeds with seeds of pepper in media containing 0, 5, 10, 15 and 20 mg l–1 BAP inhibited somatic embryogenesis in tomato and aubergine instead of assisting somatic embryogenesis in pepper. This is discussed in relation to the recent findings for the induction of somatic embyrogenesis in peanut (Arachis hypogea L.) and the role of BAP and TDZ.

ESTUDOS SOBRE A CULTURA DE TECIDOS MARACUJAZEIRO AMARELO (Passiflora edulis F. Flavicarpa DEG.)

Com o objetivo de estudar as técnicas de propagação vegetativa in vitro do maracujazeiro (Passiflora edulis f. flavicarpa Deg.) vários ensaios foram propostos. Iniciou-se com o cultivo de explantes foliares e microestacas de material adulto. Foi utilizado o meio de cultura MS com várias concentrações de BAP: 0,5; 0,75; 1,0; 1,25; 1,5; 2,0; 2,5; 3 mg.L-1 e o acesso '156 x 180' de maracujazeiro, para realizar regeneração de gemas adventícias. Determinou-se a concentração de 2 mg.L-1, a qual foi testada para os demais acessos. A porcentagem de explantes com gemas ocorreu na seguinte proporção: '156 x 123' - 64%; '156 x 180' - 40%; '352' - 30%; ('156 x 123') x ('118 x 204') - 28%; '309' - 0%. Porém, as gemas formadas eram pequenas, não alongaram e tornaram-se cloróticas. Na microestaquia com material adulto, foram testados meios com e sem auxinas, o enraizamento foi obtido com AIB 3mg.L-1 e 0,5 mg.L-1 de ANA na proporção de 60% para o acesso '352' -; 40% para '309' e ('156 x 123') x ('118 x 204') para - '156 x 123' e '156 x 180'; porém não houve desenvolvimento da parte aérea. Realizou-se também ensaios de germinação de sementes in vitro de maracujá amarelo. Para estes ensaios foram avaliados os efeitos de diferentes substratos e temperaturas. O delineamento experimental utilizado foi inteiramente casualizado, com esquema fatorial (3 x 3) e três repetições. Avaliou-se a porcentagem de germinação após 18 dias. O melhor resultado foi obtido com o tratamento de pré-embebição das sementes por 48 horas e o regime de temperaturas alternadas de 23-30ºC em substrato de algodão (86.7%). Foi avaliado também o efeito de diferentes complexos vitamínicos na regeneração in vitro do maracujá, utilizando folhas cotiledonares. Quatro tratamentos foram testados. Dois testaram o complexo vitamínico MS, e outros dois testaram o complexo vitamínico do meio B5 ambos suplementados com 1 e 2 mg.L-1 de BAP. Os meios foram solidificados com 2,6 g.L-1 de Phytagel. Cada ensaio foi substituído de 10 plantas de petri, totalizando 60 explantes por meio de cultura testado. Plântulas in vitro foram utilizadas para um ensaio de microestaquia sendo 10 tubos de ensaio com meio e vitaminas MS e 10 tubos com meio MS com vitaminas do complexo B5, com 1 microestaca em cada. As médias foram comparadas pelo teste de Tukey a 5% de probabilidade. A regeneração de plantas ocorreu via organogênese direta. Meios suplementados com complexo vitamínico B5 demonstraram aumento na capacidade regenerativa de maracujazeiro amarelo em ambas as doses de fitorreguladores, tanto em relação ao número de explantes com gemas, quando ao número de gemas por explante. O enraizamento dos brotos regenerados variou de 80-93%. A fase de aclimatação ocorreu sem perdas. As microestacas desenvolveram-se e enraizaram sem a necessidade da adição de fitorregularoes aos meios de cultura. Não houve diferenças significativas entre os resultados deste ensaio. O número de cromossomos das plantas regeneradas foi determinado pelo método de Feulgen. As plantas regeneradas apresentaram 2n=18 cromossomos.

Regeneration of soybean via embryogenic suspension culture

In an attempt to establish an alternative plant regeneration system for soybean [Glycine max (L.) Merrill] cultivars used in Brazilian breeding programs, ten genotypes were tested for their embryogenic potential. Cotyledons were removed as explants from immature seeds harvested from field-grown plants. After 45 days on induction medium, the number of responding cotyledons and the number of somatic embryos per immature cotyledon were evaluated. The percentage of explants that produced somatic embryos varied from 1 to 70% among cultivars. The average number of somatic embryos produced per cotyledon pair ranged from 0.01 to 10.3 with a mean of 3.4. Suspension cultures were initiated with three Agrobacterium tumefaciens susceptible cultivars. Suspensions were successfully developed from Bragg and IAS5 cultivars. The packed cell volume, in one-month growth, increased 8.1 fold for Bragg and 3.5 fold for IAS5 and the fresh weight increased 6.6 and 2.8 fold, respectively. The cultivars differed for the analysed parameters. All tissue from each cultivar was transferred to the maturation medium and subsequently to the germination medium. The germination frequency was 45.7 and 54.9% for Bragg and IAS5, respectively. Plants were gradually exposed to ambient humidity over one week and then planted in soil. All plants yielded seeds in the greenhouse.

In vitro root differentiation and essential-oil accumulation in Angelica archangelica

We studied the relationship between root differentiation and the accumulation of essential oils in Angelica archangelica in in vitro cultures and in the intact plant. Root regeneration was obtained using stem and leaf explants subjected to treatment with the auxins indole-3-butyric acid, indole-3-acetic acid and α-naphthaleneacetic acid. In both stem and leaf explants, treatment with indole-3-butyric acid induced the highest rhizogenic response in terms of both percentage of explants with roots and number of roots per explant. Independently of hormonal treatment, stem explants produced a higher average number of roots per explant. Root meristemoids were already visible at day 7 of culture in the treatments with indole-3-butyric acid and indole-3-acetic acid; they were formed directly by cambial-cell division. In vitro-regenerated roots retained primary root structure and differentiated only two primary ephemeral ducts in the pericycle; no accumulation of essential oils was detected. Same-size roots taken from the intact plant showed secondary structure and essential-oil accumulation. The results of this study suggest that the synthesis and accumulation of essential oils in Angelica archangelica is closely linked to the differentiation of secondary secretory ducts.

Interaction between Explant Size and Cultivar Affects Shoot Organogenic Competence of Watermelon Cotyledons

Organic competence of different explant sizes and locations on watermelon seedlings was determined by calculating the percentage of cotyledon explants that produced adventitious shoots. About 52% (214/412) of explants prepared from the proximal region of cotyledons formed shoots, whereas only ≈6% (24/411) of distal explants did so. Shoot formation was limited to the proximal end of basal explants but was not restricted to any specific region on distal ones. The percentage of explants that produced harvestable shoots was greater from basal halves than basal quarters in `Sweet Gem', `Crimson Sweet', and `Minilee', but explant size did not affect adventitious shoot regeneration of `Yellow Doll', resulting in significant interaction between cultivar and explant size. This study indicates that cultivars that respond poorly to in vitro procedures may have fewer cells competent for shoot regeneration, requiring special care during explant preparation.

315 Alstroemeria Plants Free of Alstroemeria Mosaic Potyvirus (AIMN) through in Vitro Culture Shoots and Thermotherapy

Alstroemeria (Alstroemeria spp.) is cultivated for cut flowers. Traditional propagation methods are by division of rhizomes from mature plants, so that viruses occurring in the crop can be multiplied and cause a decrease in the quality and production. The objective of this work was to obtain Alstroemeria cv. Rosario plants free of Alstromeria Mosaic Potyvirus (AlMV) by in vitro culture of shoots and thermotherapy. The best percentage of explants without contamination was obtained when adding the disinfectant PPM (1%) to the medium Murashige-Skoog (MS) while the best induction of buds was obtained when using explants of 1.5 cm. in length. In vitro multiplication of shoots was best in treatments with 2iP (isopentenyl adenine), BA (benzyladenine), and zeatin (4.4, 6.1, and 6.6 buds per explant, respectively). Rhizogenesis was observed in rhizomes growing in MS with 4.9 μM AIB (indole butyric acid) and 1.5 g·L-1 of sugar. Sixty-seven percent of plants growing in vitro did not react to AlMV antiserum and did not show particles and viral inclusions. Thermotherapy treatments of 45, 50, and 55 °C during different periods of time produced from 25% to 87.5% of plants that did not react to AlMV antiserum and did not show virus particles or cytoplasmic inclusions.

Field and in vitro methods of propagation of the African locust bean tree (Parkia biglobosa (Jacq.) (Benth.)

SummaryStem cutting in non-mist propagators, air layering and in vitro propagation were investigated as means of vegetative propagation of Parkia biglobosa. The results of the non-mist propagation experiment show that it is possible to root single-node stem cuttings from juvenile P. biglobosa plants in non-mist propagators. The highest percentage of rooting (35%) was achieved by the application of 1000 g m±3 IBA and NAA. Propagation of single-node stem cuttings from mature trees was, however, not a success. The results from the air layering experiment indicate that it is also possible to propagate P. biglobosa by air layering. The application of hormone (200 g m±3 IBA and NAA) produced the highest percentage of rooting of air layers (16%). The results of the in vitro propagation experiment reveal that the method offers an alternative opportunity for rapid multiplication of the tree. MS medium supplemented with 6.mg.l±1 IAA was the best for shoot initiation (81.7%) whereas 4±5 mg l±1 IAA gave the highest percentage of explants with roots (8.3%). Root promotion did not correspond well with IBA in both MS and WPM media. Transplanted in vitro rooted shoots were well acclimatized in the greenhouse and all plantlets exhibited some mature characteristics including compound leaves and multiple roots.

Biochemical and phenotypical characterization of transgenic tomato plants overexpressing a basic peroxidase

Tomato plants (Lycopersicon esculentum Mill. cv. Pera) were transformed via Agrobacterium tumefaciens with the binary vector pKYLX71 containing a tomato basic peroxidase (EC 1.11.1.7) gene, tpx1, under the control of the cauliflower mosaic virus (CaMV35S) promoter. Transgenic plants showed a 2–5‐fold increase in the activity of the peroxidase ionically bound to the cell wall, whereas soluble peroxidase activity remained similar or even lower than wild‐type plants. Isoelectric focusing showed the presence of a new isoperoxidase of pI ca 9 in the ionically bound extract. Western blot also showed the presence of a new band at 41 kDa that was absent in the wild‐type extract. A 40–220% increment of lignin content of the leaf was found in transgenic plants. Shoot phenotype of transgenic plants was similar to wild type, although under stress, the plants appeared wilted and the new leaves had a reduced area and were thicker than wild‐type or older transgenic leaves. The root system was underdeveloped in transgenic plants, but the rooting ability of the stem was not affected by the overexpression of peroxidase. Finally, the morphogenetic response of cotyledon and hypocotyl explants from transgenic plants was evaluated. In the case of cotyledons, the percentage of explants with shoot was not different from wild‐type plants. For hypocotyl, one of the transgenic lines showed a 30% reduction in the percentage of shoot organogenesis. The results are discussed in relation to the role of tpx1 in lignin synthesis.

Dark pretreatment improves adventitious shoot organogenesis from cotyledons of diploid watermelon

The influence of light incubation during embryo germination on shoot organogenesis from cotyledons of four diploid watermelon [Citrullus lanatus (Thumb.) Matsum. & Nakai cultivars was examined. Germinating embryos in darkness significantly improved the number of explants that produced harvestable shoots during the 6 week incubation period on shoot regeneration medium under a 16-h photoperiod. The percentage of explants with shoots more than doubled for `Crimson Sweet' and was about 1.5-fold greater for `Sweet Gem' and `Yellow Doll' when embryos were germinated in darkness. The percentage of explants with shoots was not significantly improved for `Minilee' by pretreating seedlings in darkness. This study demonstrates that optimal shoot regeneration can be obtained by germinating embryos in darkness before preparing cotyledon explants.

THE EFFECT OF EXOGENOUS POLYAMINES ON SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM SORGHUM BICOLOR AND SACCHARUM SPP.

ISHS International Symposium on Biotechnology of Tropical and Subtropical Species Part 2 THE EFFECT OF EXOGENOUS POLYAMINES ON SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM SORGHUM BICOLOR AND SACCHARUM SPP.

Adventitious shoot induction from leaf explants of Ribes magellanicum cultured in vitro

Several factors were studied on adventitious shoot induction from leaf explants of Ribes magellanicum cultured in vitro: type of explant, position of the leaves along the stem and growth regulators. Explants with petiole and complete leaf lamina presented the highest percentage of organogenesis. The position of the leaf along the shoot strongly affected the induction capacity. The percentage of explants with adventitious shoots was maximum (53%) when using apical leaves, with an average of three shoots per explant. 6-benzylaminopurine (BA) and N-benzyl-9-(2-tetrahydropyranyl)-adenine (BPA) had a significantly higher promotive effect than 6-(τ-τ-dimethylallylamino) purine (2iP) or kinetin on induction of adventitious shoots. Cytokinin concentration significantly affected shoot production, best responses being obtained with 4.44 to 8.88 μM. No significant differences were observed between α-naphthaleneacetic acid (NAA) concentrations but 0.5 μM NAA usually promoted the highest number of non-vitrified shoots per explant. The results of this work show that R. magellanicum can be induced to form adventitious shoots from leaf explants cultured in vitro.