Plant regeneration from excised hypocotyl explants of <Emphasis Type="Italic">Platanus acerifolia</Emphasis> willd

Summary A method of plant regeneration from hypocotyl segments of Platanus acerifolia Willd, has been developed. Hypocotyl slices were cultured on Murashige and Skoog (MS) basal medium supplemented with a range of combinations of cytokinins [6-benzyladenine (BA) or kinetin] and auxins [indole-3-butyric acid (IBA), indole-3-acetic acid, α-naphthaleneacetic acid or 2,4-dichlorophenoxyacetic acid] for adventitious shoot induetion. The highest regeneration frequency was obtained with MS medium containing 2.0 mg l⁻¹ (8.88 μM) BA and 0.5 mg l⁻¹ (2.46 μM) IBA. Adventitious buds and shoots were differentiated from hypocotyl-derived cellus or directly from the wounded sites within 4–8 wk. The regenerated shoots were elongated and proliferated efficiently on multiplication medium. Complete plantlets were transplanted to the soil and grew normally in the greenhouse after root formation on rooting medium for 4–6 wk.     

Liquid culture for efficient micropropagation of Wasabia Japonica (MIQ.) matsumura

Summary An efficient protocol for in vitro propagation of the valuable medicinal plant, Wasabia japonica (Miq.) Matsumura is described through shoot tip proliferation and direct regeneration. Multiple shoots were induced from shoort tips cultured on Murashige and Skoog (MS) semi-solid medium containing various concentrations (0.5–50 μM) of N⁶-benzyladenine (BA), thidiazuron, kinetin, and zeatin. A comparison was made on shoot multiplication between semi-solid and liquid culture media. Well-developed shoots were obtained using full-strength MS semi-solid medium containing 5.0 μM BA. However, the greatest shoot proliferation was achieved on either full- or half-strength MS liquid media supplemented with 5.0 μM BA for 4 wk (15.3±0.9 and 15.0±0.7 shoots per explant, respectively), and on half-strength MS liquid medium for 6 wk (25.8±1.3 shoots per explant) in culture. In contrast, the maximum number of shoots per explant on full-strength MS semi-solid medium was achieved with either 5.0 μM BA (10.4±0.6 shoots per explant) or 10.0 μM kinetin (10.9±0.8 shoots per explant). Fresh weight of explants and length of shoots derived from full-strength MS liquid medium (1055±77 mg and 34.2±1.0 mm, respectively) were significantly higher than those derived from full-strength MS semisolid medium (437.6±17.3 mg and 15.4±0.7 mm, respectively). Quarter-strength MS liquid medium had no significant difference in shoot proliferation when compared to quarter-strength MS semi-solid medium. Elongated shoots were separated and rooted on half-strength MS semi-solid media fortified with 1-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), or indole-3-acetic acid (IAA) ranging from 0.1 to 10.0 μM. Root formation was greatest with IBA when compared with IAA and NAA. One hundred percent of shoots were rooted on half-strength MS medium with 5.0 μM IBA, while vigorous roots were obtained with 10.0 μM IBA. Micropropagated plantlets were successfully established in soil with 95% survival rate after heardening.     

Cytokinins,auxins and activated charcoal affect organogenesis and anatomical characteristics of shoot-tip cultures of lisianthus [<Emphasis Type="Italic">Eustoma grandiflorum</Emphasis> (RAF.) Shinn]

Summary Variants from seed-propagated Lisianthus [Eustoma grandiflorum (Raf.) Shinn] were shoot-tip cultured to observe the effects of cytokinins, auxins and activated charcoal on organogenesis and anatomical characteristics. N⁶-Benzyladenine (BA) and kinetin at high concentrations (13.32–22.2 and 13.94–23.23 μM) resulted in good shoot formation but high percentages of hyperhydric shoots. Increased indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) concentrations favored root formation, while increased naphthaleneacetic acid concentration adversely affected root formation. Both shoot and root development were suppressed by activated charcoal. The highest percentage of regeneration and the largest number of glaucous shoots with an average of 15 shoots per explant after 4 wk of culture were obtained when the shoot tips were cultured on MS (Murashige and Skoog, 1962) medium supplemented with 4.44 μM BA and 1.47–4.92 μMIAA and IBA. In vitro-grown leaves had a higher number of stomata than field-grown leaves but the length and diameter of stomata showed no significant difference between the two types. Field-grown leaves had well-developed epicuticular wax layers. which were not observed on hyperhydric leaves. Hyperthydric plantlets could not survive when transplanted to soil, whereas glaucous plantlets survived in more than 80% of cases. Variation in soil type resulted in a slight difference in plantlet survival. Based on the results of our experiment, this protocol should be useful for the rapid micropropagation of lisianthus.     

<Emphasis Type="Italic">In vitro</Emphasis> shoot regeneration from cotyledonary node explants of a multipurpose leguminous tree, <Emphasis Type="Italic">Pterocarpus marsupium</Emphasis> roxb

Summary A protocol has been developed for in vitro plant regeneration from cotyledonary nodes of Pterocarpus marsupium Roxb. Multiple shoots were induced from cotyledonary nodes derived from 20-d-old axenic seedlings grown on Murashige and Skoog (MS) medium containing 2.22–13.32 μM benzyladenine (BA) or 2.32–13.93 μM kinetin alone or in combination with 0.26 μM α-naphthaleneacetic acid (NAA). The highest frequency for shoot regeneration (85%) and maximum number of shoots per explant (9.5) were obtained on the medium supplemented with 4.44 μM BA and 0.26 μM NAA after 15 wk of culture. A proliferating shoot culture was established by repeatedly subculturing the original cotyledonary nodal explant on fresh medium after each harvest of the newly formed shoots. Nearly 30% of the shoots formed roots after being transferred to half-strength MS medium containing 9.84 μM indole-3-butyric acid (IBA) after 25 d of culture. Fifty percent of shoots were also directly rooted as microtuttings on a peat moss, soil, and compost mixture (1∶1∶1). About 52% of plantlets were successfully acclimatized and established in pots.     

<Emphasis Type="Italic">In vitro</Emphasis> shoot regeneration from cotyledonary node explants of a multipurpose leguminous tree <Emphasis Type="Italic">Pterocarpus marsupium</Emphasis> Roxb.

Summary A protocol has been developed for in vitro plant regeneration from cotyledonary nodes of Pterocarpus marsupium Roxb. Multiple shoots were induced from cotyledonary nodes derived from 20-d-old axenic seedlings grown on Murashige and Skoog (MS) medium containing 2.22–13.32 μM benzyladenine (BA) or 2.32–13.93 μM kinetin alone or in combination with 0.26 μM α-naphthaleneacetic acid (NAA). The highest frequency of responding explants (85%) and maximum number of shoots per explant (9.5) were obtained on MS medium supplemented with 4.44 μM BA and 0.26 μM NAA after 15 wk of culture. A proliferating shoot culture was established by repeatedly subculturing the orginal cotyledonary nodal explant on fresh medium after each harvest of the newly formed shoots. Nearly 30% of the shoots formed roots after being transferred to half-strength MS medium containing 9.84 μM indole-3-butyric acid after 25 d of culture. Fifty percent of shoots were also directly rooted as microcuttings on peat moss, soil, and compost mixture (1∶1∶1). About 52% plantlets rooted under ex vitro conditions were successfully acclimatized and established in pots.     

Efficient production of protocorm-like bodies and plant regeneration from flower stalk explants of the sympodial orchid <Emphasis Type="Italic">Epidendrum radicans</Emphasis>

Summary A simple and efficient micropropagation method was established for direct protocorm-like body (PLB) formation and plant regeneration from flower stalk internodes of a sympodial orchid, Epidendrum radicans. Small transparent tissues formed on surfaces and cut ends of flower stalk internodes on a modified half-strength Murashige and Skoog basal medium with or without thidiazuron (TDZ) after 1–2 wk of culture. In the light, the transparent tissues enlarged and turned into organized calluses on most of the explants. However, PLBs formed only on a medium supplemened with 0.45 μM TDZ within 2 mo. of culture. Sucrose, NH₄NO₃, and KNO₃ were used in media to test their effects on PLB proliferation and shooting. The best response on number of PLBs per tube was 23.6 at 40 gl⁻¹ sucrose, 825 mgl⁻¹ NH₄NO₃, and 950 mgl⁻¹ KNO₃, and the highest number of PLBs with shoots was found at 10 gl⁻¹ sucrose, 825 mgl⁻¹ NH₄NO₃, and 950 mgl⁻¹ KNO₃. Homogenized PLB tissues produced by blending were used to test the effects of four cytokinins [TDZ, N⁶-benzyladenine (BA), zeatin-riboside, and kinetin] on PLB proliferation and shoot formation. The best responses on number of PLBs per tube, proliferation rate, and number of PLBs with shoots per tube were obtained at 4.44 μM BA, 0.28 μM zeatin-riboside, and 1.39 μM kinetin, respectively. Normal plantlets converted from PLBs on the same TDZ-containing medium after 1 mo. of culture. The optimized procedure required about 12–13 wk from the initiation of PLBs to plantlet formation. The regenerated plants grew well with an almost 100% survival rate when acclimatized in a greenhouse.     

Micropropagation of <Emphasis Type="Italic">Metrosideros excelsa</Emphasis>

Multiple shoots were induced on stem segments of an 8-y-old plant of Metrosideros excelsa Sol ex Gaertn. “Parnel”. Axillary shoots produced on uncontaminated explants were excised, segmented, and recultured in the same medium to increase the stock of shoot cultures. The Murashige and Skoog (MS) medium, augmented with different concentrations of 2- isopenthenyladenine (2iP) and indole-3-acetic acid (IAA), either singly or in combinations, as potential medium for shoot multiplication by nodal segments was tested. In the following experiment, equal molar concentrations of four cytokinins [2iP, kinetin, zeatin, and N ⁶-benzyladenine (BA)] in combination with equal molar concentrations of three auxins [IAA, α-naphthaleneacetic acid (NAA), and indole-3-butyric acid (IBA)] were tested for ability to induce axillary shoot development from single-node stem segments. The highest rate of axillary shoot proliferation was induced on MS agar medium supplemented with 1.96μM 2iP and 1.14μM IAA after 6 wk in culture. Different auxins (IAA, IBA, and NAA) were tested to determine the optimum conditions for in vitro rooting of microshoots. The best results were accomplished with IAA at 5.71μM (89% rooting) and with IBA at 2.85 or 5.71μM (86% and 86% rooting, respectively). Seventy and 90 percent of the microshoots were rooted ex vitro in bottom-heated bench (22 ± 2°C) after 2 and 4 wk, respectively. In vitro and ex vitro rooted plantlets were successfully established in soil.     

Micropropagation of <Emphasis Type="Italic">Penthorum chinense</Emphasis> through axillary bud

This study reports a protocol for successful micropropagation of Penthorum chinense using nodal explants on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA) or kinetin (Kn). The presence of BA promoted a higher rate of shoot multiplication than Kn. Maximum multiple shoot formation was observed in 59.2% of nodal explants cultured on MS medium supplemented with 2.0 mg l⁻¹ BA after 6 wk. After subculture for 4 wk, the maximum number of shoots (6.4) was obtained on a medium with 2.0 mg l⁻¹ BA, but shoots were too short and not suitable for micropropagation. The taller shoots that regenerated in the presence of lower BA concentration (1.0 mg l⁻¹) were selected for root induction study. Most shoots (98.8%) rooted in the presence of 0.5 mg l⁻¹ indole-3-acetic acid after 3 wk, with each shoot forming an average of 10.0 roots. Plantlets were transferred to soil and successfully acclimatized.     

A two-step procedure for adventitious shoot regeneration on excised leaves of lowbush blueberry

An efficient system to regenerate shoots on excised leaves of greenhouse-grown wild lowbush blueberry (Vaccinium angustifolium Ait.) was developed in vitro. The effect of thidiazuron (TDZ) on adventitious bud and shoot formation from apical, medial, and basal segments of the leaves was tested. Leaf cultures produced multiple buds and shoots with or without an intermediary callus phase on 2.3–4.5 μM TDZ within 6 wk of culture initiation. The greatest shoot regeneration came from young expanding basal leaf segments positioned with the adaxial side touching the culture medium and maintained for 2 wk in darkness. Callus development and shoot regeneration depended not only on the polarity of the explants but also on the genotype of the clone that supplied the explant material. TDZ-initiated cultures were transferred to medium containing 2.3–4.6 μM zeatin and produced usable shoots after one additional subculture. Elongated shoots were dipped in 39.4 mM indole-3-butyric acid powder and planted on a peat:perlite soilless medium at a ratio of 3:2 (v/v), which yielded an 80–90% rooting efficiency. The plantlets were acclimatized and eventually established in the greenhouse with 75–85% survival.     

<Emphasis Type="Italic">In vitro</Emphasis> organogenesis of <Emphasis Type="Italic">Pelecyphora aselliformis</Emphasis> erhenberg (cactaceae)

Summary In vitro propagation of Pelecyphora aselliformis, a Mexican cactus which is considered rare and is highly valued in the commercial market, was initiated using seeds as explants. The longitudinal explants from seedlings germinated in vitro were cultivated on Murashige and Skoog medium containing 8.8 μM benzyladenine (BA) or 4.6 μM kinetin at pH 7.0. After 120 d, each explant gave rise to five shoots and this number of shoots increased 20–25% after subculture. The hyperhydricity was similar in both media, but callus formation was lower on the medium with BA. The shoot development, in terms of epicotyl length, and fresh and dry weight after 6 wk, was also recorded. The epicotyl length was similar on shoot-forming media but the quality of shoots was better on media containing BA. In about 1 yr, 500–600 well-defined shoots were obtained. The rooting of shoots was very slow and a vigorous radical system was observed after 1 yr of culture.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation and cryostorage of <Emphasis Type="Italic">Syzygium francissi (Myrtaceae)</Emphasis> by the encapsulation-dehydration method

Summary An efficient procedure for the in vitro propagation and cryogenic conservation of Syzygium francissi was developed. The maximum number of shoots per explant was obtained on a Murashige and Skoog (MS) medium supplemented with 4.5 μM benzyladenine and 0.5 μM indole-3-butyric acid (IBA). The in vitro-propagated shoots produced roots when transferred to MS medium containing IBA, indold-3-acetic acid, or naphthaleneacetic acid at various concentrations. Rooted microshoots were transferred to a coco-peat, perlite, and vermiculite (1∶1∶1) mixture, and hardened off under greenhouse conditions. Ninety-five percent of rooted shoots successfully acclimatized in the greenhouse. Shoot tips excised from in vitro-grown plants were successfully cryostoraged at −196°C by the encapsulation-dehydration method. A preculture of formed beads on MS medium containing 0.75 M sucrose for 1 d, followed by 6 h dehydration (20% moisture content) led to the highest survival rate after cryostorage for 1h. This method is a promising technique for in vitro propagation and cryopreservation of shoot tips from in vitro-grown plantlets of S. francissi germplasm.     

Identification of highly regenerative plants within sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.) breeding lines for molecular breeding

Summary Development of an efficient transformation method for recalcitrant crops such as sugar beet (Beta vulgaris L.) depends on identification of germplasm with relatively high regeneration potential. Individual plants of seven sugar beet breeding lines were screened for their ability to form adventitious shoots on leaf disk callus. Disks were excised from the first pair of true leaves of 3-wk-old seedlings or from partially expanded leaves of 8-mo.-old plants and cultured on medium with 4.4 μM 6-benzylaminopurine for 10 wk. At 5 wk of culture, friable calluses and adventitious shoots began to develop. Rates of callus and shoot formation varied between breeding lines and between individual plants of the same line. Line FC607 exhibited the highest percentage (61%) of plants that regenerated shoots on explants. Among the plants with a positive shoot regeneration response, line FC607 also had the highest mean number (8.3±1.1) of shoots per explant. Individual plants within each line exhibited a wide range of percentages of explants that regenerated shoots. A similar variation was observed in the number of shoots that regenerated per explant of an individual plant. No loss of regeneration potential was observed on selected plants maintained in the greenhouse for 3 yr. Regenerated plants exhibited normal phenotypes and regeneration abilities comparable to the respective source plants. Based on our results, it is imperative to screen a large number of individual plants within sugar beet breeding lines in order to identify the high regenerators for use in molecular breeding and improvement programs.     

Direct shoot regeneration from leaf explants of <Emphasis Type="Italic">Rosa damascena</Emphasis> Mill.

Summary A protocol for in vitro propagation using direct induction of shoot buds from leaf explants of in vitro-raised shoots of Rosa damascena var. Jwala is reported. The present study is the first report on direct shoot regeneration in scented roses. Elite plants raised from nodal explants and maintained for over 2yr in vitro on a static liquid shoot multiplication Murashige and Skoog (MS) medium supplemented with 5.0 μM benzyladenine (BA) and 3% sucrose were used. Petioles from fully developed young leaves, obtained after 4 wk of pruning of old shoots, were found to be ideal for regeneration of shoots. Initially the explants were cultured in an induction medium [half-strength MS+3% sucrose+6.8μM thidiazuron+0.27 μM α-naphthaleneacetic acid (NAA)+17.7 μM AgNO₃] and subsequently transferred to the regeneration medium (MS+2.25 μM BA+0.054 μM NAA) after 7, 14, 21, 28, and 35d. The highest shoot regeneration response (69%) was recorded when shoots were kept in the induction medium for 21 d and later transferred to regeneration medium. Histological studies revealed direct formation of shoot buds without the intervening callus phase. In vitro rooting of micro-shoots was accomplished within 2wk on half-strength MS liquid medium supplemented with 10.0 μM IBA and 3% sucrose for 1 wk in the dark and later transferred to hormone-free medium and kept in the light. Plantlets, remaining in the latter medium for 5–6 wk when transferred to soil, showed 90% survival.     

Rapid in vitro multiplication and plant regeneration from nodal explants of Andrographis paniculata: a valuable medicinal plant

A rapid and efficient method for the large-scale propagation of a highly valuable medicinal plant, Andrographis paniculata Nees, through in vitro culture of nodal explants obtained from 15-d-old aseptic seedling has been developed. High frequency direct shoot proliferation was induced in nodal explants cultured on Murashige and Skoog’s medium supplemented with 6-benzylaminopurine (BAP). Amongst the various cytokinins tested (BAP, kinetin, thidiazuron and 2-isopentyl adenine), BAP proved to be the most effective. The shoot forming capacity of the nodal explants was influenced by the BAP concentration (1–12.5 μM), and the optimal response was observed at 10 μM BAP, which induced an average of 34 shoots in 94% of the cultures within 4 wk. Significant differences were recorded in terms of average number of shoots per explant (8.6–34.1) among the different concentrations of BAP investigated. Concentrations of all cytokinins tested reach a level that can be considered above the optimum level, as marked by a reduced frequency of shoot proliferation. The multiple shoots obtained on various concentrations of BAP failed to elongate even after transfer to hormone-free MS medium. Elongation of the induced shoots was achieved on MS basal medium supplemented with 1.0 μM GA₃ within 2 wk. A proliferating shoot culture was established by repeatedly subculturing the original nodal explants on shoot multiplication medium after each harvest of the newly formed shoots. The explants retained their morphogenic potential even after three harvests. Therefore, in 90 d, about 60–70 shoots were obtained from a single nodal explant and the nodal explants from primary shoots further regenerated equivalent number of shoots, depicting their high frequency regeneration potential in A. paniculata. Rooting was best induced in 94% of shoots cultured on MS medium supplemented with 2.5 μM indole-3-butyric acid (IBA), within a wk. The plantlets were successfully transferred to soil after hardening with a 92% survival rate. The system is rapid: the initiation of shoot buds to the transplanting of regenerants to soil is completed in 8–9 wk.     

In vitro micropropagation and ex vitro acclimation of Bupleurum kaoi-an endangered medicinal plant native to Taiwan

Summary This study reports an improved protocol for in vitro-shoot multiplication and ex vitro acclimation of Bupleurum kaoi, an endangered medicinal herb. Nodal segments were cultured in half-strength Murashige and Skoog (MS) basal medium supplemented with different concentrations of benzyladenine (BA) and kinetin. The presence of 0.25 mg l⁻¹ BA induced the highest number of shoots per explant after 8 wk of culture. Although BA was more effective than kinetin on shool multiplication, it induced hyperhydric shoots at all concentrations tested. The use of dispense paper (DP) instead of aluminum foil (AF) for container closure was found to reduce hyperhydricity and improve ex vitro acclimation. The best survival rate (61%) was obtained when plantlets were grown in MS basal medium containing 0.5 mg l⁻¹ indole-3-butyric acid and 0.1–0.2 mg l⁻¹ α-naphthaleneacetic acid using DP as container closure. Leaves of the plant treated with AF6 (two layers of AF as container closure and 6 wk of incubation) lacked epicuticular wax and possessed larger stomata, higher stomata density, and fewer functional stomata compared to those of plants treated with AF2+DP4 (two layers of AF for 2 wk, then replaced AF by three layers of DP for 4wk) and ex vitro-acclimated plantlets.     

Plant regeneration from protocorm-derived callus of <Emphasis Type="Italic">Cypripedium formosanum</Emphasis>

Summary Totipotent callus of Cypripedium formosanum, an endangered slipper orchid species, was induced from seed-derived protocorm segments on a quarter-strength Murashige and Skoog medium containing 4.52 μM 2,4-dichlorophenoxyacetic acid and 4.54 μM 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (thidiazuron). This callus proliferated well and was maintained by subculturing on the same medium. On average, 13 protocorm-like bodies could be obtained from a piece of 4 mm callus after being transferred to the medium with 4.44 μM N⁶-benzyladenine after 8 wk of culture. The regenerated protocorm-like bodies formed shoots and roots on medium containing 1 g l⁻¹ activated charcoal and 20 g l⁻¹ potato homogenate. After 24 wk of culture on this medium, well-developed plantlets ready for potting were established.     

TDZ-induced high frequency plant regeneration through multiple shoot formation in witloof chicory (<Emphasis Type="Italic">Cichorium intybus</Emphasis> L.)

A very efficient and rapid regeneration system via multiple shoot formation was developed for Cichorium intybus L. when leaf explants excised from sterile seedlings were cultured on medium supplemented with different concentrations and combinations of various plant growth regulators. In a comparison of leaf lamina and petiole explants, lamina explants produced over three times more shoots than petiole explants, with a mean of 7.5 shoots compared to 2.4. Of the combinations of KIN/IAA, KIN/NAA, BAP/IAA, or BAP/NAA, 0.5 mg l⁻¹ KIN combined with 0.3 mg l⁻¹ IAA was the most effective, producing a mean of 19.7 shoots per lamina explant while the control treatment involving no plant growth regulators produced no shoots at all. When either cytokinin was used alone, BAP was found nearly twice more successful than KIN. However, the most effective treatment of all was the combination of 0.01 mg l⁻¹ TDZ and 1.0 mg l⁻¹ IAA, producing as many as 35.8 shoots per lamina explant. This rate of shoot regeneration is remarkably higher than those previously reported for C. intybus, most likely due to the highly inductive effect of TDZ, which was tested for the first time in this species. Rooting of the shoots was readily achieved on medium containing different concentrations of IAA or IBA. IAA was more effective than IBA and resulted in the highest frequency of shoots that rooted (100%) and mean number of roots per shoot (4.2) when used at 0.5 mg l⁻¹. Hardening off process resulted in a production of more than 80% healthy plantlets.     

<Emphasis Type="Italic">In vitro</Emphasis> micropropagation of four lupin species

The complete protocols for long-term micropropagation of some cultivars of four lupin species: Lupinus luteus, L. albus, L. angustifolius and L. mutabilis were elaborated. The shoots were regenerated in vitro via induction of axillary buds development. Plantlets were multiplicated on lowered salts MS-derived media containing BAP in diverse and generally low concentrations. Significant differences in regeneration capacity between species and cultivars were observed. The highest multiplication ratio revealed L. mutabilis and L. luteus. Regenerated shoots were rooted in vitro on low-salts MS-derived media with B5 vitamins. Media were supplemented with different auxins that affected roots formation of particular species and cultivars. Rooting ability of regenerated shoots decreased rapidly through in vitro culture. For that reason, grafting was applied as an alternative method of transfer of shoots to in vivo conditions. This method turned out to be successful for the majority of studied species and cultivars. Complete rooted or grafted plantlets were cultivated in pots with perlit in greenhouse. An erratum to this article is available at .     

Regeneration of plantlets from leaf and petiole explants of Pelargonium x hortorum

Summary The in vitro plant regeneration potential of vegetatively propagated geraniums (Pelargonium x hortorum) has been investigated. Using various combinations of growth regulators and a choice of different explants, a regeneration protocol has been developed to raise in vitro plantlets from young petiole and leaf explants from three different cultivars of geraniums. In all three cultivars, very young petiole explants exhibited a higher regeneration potential as compared with leaf explants. Regeneration efficiencies were found to be highly dependent on the cultivar, with cv. Samba showing the highest regeneration potential, followed by cvs. Yours Truly and then Sincerity. Samba also showed the highest number of shoots from both the petiole [57 shoot buds per petiole explant in the presence of 3 μM zeatin and 1 μM indole-3-acetic acid (IAA) and leaf explants (43 shoots per leaf explant with 10 μM zeatin and 2 μM IAA). Shoot buds transferred to Murashige and Skoog (MS) medium supplemented with 0.44 μM N⁶-benzyladenine and 0.11 μM IAA grew vigorously and attained 1–2 cm in length in 3–4 wk. These shoots rooted with 100% efficiency on MS basal medium, and plants developed that showed normal growth and flowering under greenhouse conditions.