Thidiazuron stimulates adventitious shoot regeneration in different safflower explants

Adventitious shoot regeneration from root, hypocotyl, cotyledon and primary leaf explants of safflower (Carthamus tinctorius L.) was studied. Shoot regeneration was promoted by benzyladenine (BA) + naphthaleneacetic acid (NAA), BA + indole-3-butyric acid (IBA), kinetin + NAA and thidiazuron (TDZ) + NAA incorporated in Murashige and Skoog (MS) basal medium. High frequency of shoot regeneration and high number of shoots per regenerating explant were obtained on a wide range of TDZ + NAA combinations. Proliferated shoots were elongated in MS + 0.5 mg dm⁻³ kinetin and well-developed shoots were rooted in half strength MS + 0.5 mg dm⁻³ NAA. Rooted shoots were successfully acclimatized and established in soil.     

Shoot regeneration and the relationship between organogenic capacity and endogenous hormonal contents in pumpkin

To induce multiple shoots from pumpkin (Cucurbita moschata Duch.), cotyledon explants excised from various ages of seedlings after in vitro germination were cultured on MS augmented with different concentrations of BA (0, 0.5, 1.0 or 2.0 mg l⁻¹). The highest frequency of shoot regeneration (63.7%) was observed from seven-day-old cotyledon explants cultured on MS containing 0.5 mg l⁻¹ BA. The frequency and duration of shoot formation showed close correlation with the donor seedling age. By contrast, BA supply was necessary to promote shoot formation but no differences were observed in relation to different concentrations. Multiple shoots elongated on MS supplemented with 0.1 mg l⁻¹ BA and 5–7 shoots per regenerated explant were recovered. Elongated shoots were rooted on MS, which was easier than that on 2/3MS, 1/2MS, or MS supplemented with 0.1 mg l⁻¹ NAA. The rooted shoots were then transferred to greenhouse where they grew and flowered normally. Quantitative analysis of endogenous auxin (IAA) and cytokinins (iPA and ZR) in initial cotyledon explants of different aged seedlings showed that the regeneration ability of cotyledon explants varied dependently on their endogenous iPA contents. This study therefore deduces that the various organogenic capabilities of cotyledon explants from pumpkin are the result of their endogenous hormonal contents.     

Micropropagation of Sesbania rostrata from the Cotyledonary Node

Multiple shoots were induced from the cotyledonary nodes derived from seedling of Sesbania rostrata on Nitsch (1969; N) medium supplemented with various concentrations of benzyladenine (BA). 1 mg dm⁻³ BA proved to be the best, eliciting 5.8 ± 1.0 shoots per explant in 100 % cultures. The elongation of shoots was best at 2.0 mg dm⁻³ BA. The shoot proliferation capacity increased to 7.5 shoots per explant following transfer of explants to the fresh shoot multiplication medium (MS + 1.0 mg dm⁻³ BA), after an initial incubation of 30 d. To further enhance number of shoots per explant an alternative strategy of cultivation of mother explant on fresh shoot multiplication medium after excision of shoots was adopted. Following the repeated harvesting of shoots an average of 33 shoots per explant could be obtained. The in vitro regenerated shoots produced roots when transferred to half-strength MS medium supplemented with 3 % sucrose and 1 mg dm⁻³ IBA. The developed plantlets were planted in the soil and transferred to the field after an acclimatization period of 3 – 4 months. These plants produced flowers and fruits in the field and exhibited the development of prominent and more organized stem nodules as compared to the in vivo raised plants of the same age. This revised version was published online in July 2006 with corrections to the Cover Date.     

<Emphasis Type="Italic">In vitro</Emphasis> bud regeneration of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> and wild <Emphasis Type="Italic">Carthamus</Emphasis> species from leaf explants and axillary buds

The organogenic competence of leaf explants of eleven Carthamus species including C. tinctorius on Murashige and Skoog (MS) medium supplemented with different concentrations of thidiazuron (TDZ) + α-naphthaleneacetic acid (NAA) and 6-benzyladenine (BA) + NAA was investigated. Highly prolific adventitious shoot regeneration was observed in C. tinctorius and C. arborescens on both growth regulator combinations and the shoot regeneration frequency was higher on medium supplemented with TDZ + NAA. Nodal culture of nine Carthamus species on media supplemented with BA and kinetin (KIN) individually revealed the superiority of media supplemented with BA over that of KIN in facilitating a higher shoot proliferation index. Proliferating shoots from axillary buds and leaf explants were transferred to medium supplemented with 1.0 mg dm⁻³ KIN or 0.5 mg dm⁻³ BA for shoot elongation. Elongated shoots were rooted on half-strength MS medium supplemented with 1.0 mg dm⁻³ each of indole-butyric acid (IBA) and phloroglucinol. The plantlets thus obtained were hardened and transferred to soil.     

High frequency plant regeneration from cotyledon and hypocotyl explants of ornamental kale

A high frequency shoot regeneration system for ornamental kale [Brassica oleracea L. var. acephala (D.C.) Alef.] was firstly established from seedling cotyledon and hypocotyl explants. The ability of cotyledon and hypocotyl to produce adventitious shoots varied depending upon genotype, seedling age and culture medium. The maximum shoot regeneration frequency was obtained when the explants from cv. Nagoya 4-d-old seedlings were cultured on Murashige and Skoog (MS) medium supplemented with 3 mg dm⁻³ 6-benzylaminopurine (BA) and 0.1 mg dm⁻³ naphthaleneacetic acid (NAA). The frequency of shoot regeneration was 65.0 % for cotyledons, 76.1 % for hypocotyls; and the number of shoots per explant was 4.3 for cotyledons, 8.2 for hypocotyls. Hypocotyl explants were found to be more responsive for regeneration when compared with cotyledons. Among the 4 cultivars tested, Nagoya showed the best shoot regeneration response. The addition of 3.0 mg dm⁻³ AgNO₃ was beneficial to shoot regeneration. Roots were formed on the base of the shoots when cultured on half-strength MS medium.     

Direct shoot regeneration from node,internode, hypocotyl and embryo explants of Withania somnifera

In vitro studies were initiated with Withania somnifera (L.) Dun. for rapid micropropagation of selected chemotypes using nodes, internodes, hypocotyls and embryo explants. Direct regeneration of shoot buds was observed in MS basal medium supplemented with various concentrations of either benzyladenine (BA) or thidiazouron (TDZ) depending on the explant. Nodal explants formed multiple shoots both from pre-existing and de novo buds on Murashige and Skoog's medium (MS) containing 0.1–5.0 mg l⁻¹ BA and a ring of de novo shoot buds on MS medium containing 0.2 and 0.3 mg l⁻¹ TDZ. Internodal explants formed shoot buds on MS with 1.0 and 5.0 mg l⁻¹ BA while the hypocotyl explants gave rise to multiple shoots only on MS with 0.5 mg l⁻¹ BA. Isolated embryos gave rise to many shoot buds on MS with 0.2 and 0.3 mg l⁻¹ TDZ. The shoot buds elongated and rooted either on MS medium with 0.01 mg l⁻¹ BA or on half strength MS medium lacking growth regulators, which depended upon the growth regulator used in the shoot bud induction medium. Except for the embryo-derived plantlets, all other plantlets could be acclimatized with 100% success. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct shoot regeneration from leaf explants of <Emphasis Type="Italic">Spilanthes acmella</Emphasis>

Multiple shoots of Spilanthes acmella Murr. were induced from nodal buds of in vivo and in vitro seedlings on Murashige and Skoog (MS) medium containing 1.0 mg dm⁻³ 6-benzyladenine (BA) and 0.1 mg dm⁻³ α-naphthalene-acetic acid (NAA). Adventitious shoots were successfully regenerated from the leaf explants derived from the above mentioned multiple shoots. The efficiency of shoot regeneration was tested in the MS medium containing BA, kinetin, or 2-isopentenyl adenine in combination with NAA, indole-3-acetic acid (IAA), or indole-3-butyric acid (IBA) and gibberellic acid. Maximum number of shoots per explant (20 ± 0.47) was recorded with 3.0 mg dm⁻³ BA and 1.0 mg dm⁻³ IAA. An anatomical study confirmed shoot regeneration via direct organogenesis. About 95 % of the in vitro shoots developed roots after transfer to half strength MS medium containing 1.0 mg dm⁻³ IBA. 95 % of the plantlets were successfully acclimatized and established in soil. The transplanted plantlets showed normal flowering without any morphological variation.     

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.     

<Emphasis Type="Italic">In vitro</Emphasis> plant regeneration through somatic embryogenesis and direct shoot organogenesis in <Emphasis Type="Italic">Pennisetum glaucum</Emphasis> (L.) R. Br.

An efficient in vitro plant regeneration protocol through somatic embryogenesis and direct shoot organogenesis has been developed for pearl millet (Pennisetum glaucum). Efficient plant regeneration is a prerequisite for a complete genetic transformation protocol. Shoot tips, immature inflorescences, and seeds of two genotypes (843B and 7042-DMR) of pearl millet formed callus when cultured on Murashige and Skoog (MS) medium supplemented with varying levels of 2,4-dichlorophenoxyacetic acid (2,4-D; 4.5, 9, 13.5, and 18 μM). The level of 2,4-D, the type of explant, and the genotype significantly effected callus induction. Calli from each of the three explant types developed somatic embryos on MS medium containing 2.22 μM 6-benzyladenine (BA) and either 1.13, 2.25, or 4.5 μM of 2,4-D. Somatic embryos developed from all three explants and generated shoots on MS medium containing high levels of BA (4.4, 8.8, or 13.2 μM) combined with 0.56 μM 2,4-D. The calli from the immature inflorescences exhibited the highest percentage of somatic embryogenesis and shoot regeneration. Moreover, these calli yielded the maximum number of differentiated shoots per callus. An efficient and direct shoot organogenesis protocol, without a visible, intervening callus stage, was successfully developed from shoot tip explants of both genotypes of pearl millet. Multiple shoots were induced on MS medium containing either BA or kinetin (4.4, 8.8, 17.6, or 26.4 μM). The number of shoots formed per shoot tip was significantly influenced by the level of cytokinin (BA/kinetin) and genotype. Maximum rooting was induced in 1/2 strength MS with 0.8% activated charcoal. The regenerated plants were transferred to soil in pots, where they exhibited normal growth.     

Influence of plant preservative mixture (PPM)TM on adventitious organogenesis in melon, petunia, and tobacco

Summary The influence of PPM^TM on somatic embryogenesis in melon, adventitious shoot organogenesis in petunia, and androgenesis in tobacco was studied by culturing explants in regeneration media supplemented with 0, 2, 5 or 10 ml l⁻¹ PPM for 8–12 wk. The percentage of melon cotyledon explants that produced callus and somatic embryos and the number of embryos per explant were reduced when incubated in embryo initiation and embryo development media containing more than 5 ml l⁻¹ PPM. Less PPM was required to inhibit petunia shoot organogenesis. The number of shoots and number of buds per Petri dish were reduced 3–6.9-fold when leaf explants were incubated in shoot regeneration medium containing more than 2 ml l⁻¹ PPM. In contrast, the addition of up to 10 ml l⁻¹ PPM to tobacco anther culture medium had no effect on androgenesis. Our results suggest that the influence of PPM on plant regeneration depends on the plant species. We recommend that experimenters examine a range of PPM concentrations when using it for the first time on an untested plant species.     

High frequency plant regeneration from the cotyledonary node of common bean

An efficient regeneration system for Phaseolus vulgaris was developed from mature seeds germinated on Murashige and Skoog (MS) medium supplemented with thidiazuron or N⁶-benzylaminopurine (BA) for 6 d. Using cotyledonary nodes, multiple buds were induced on the MS medium supplemented with 5.0 mg dm⁻³ BA with the induction frequency 71.9 % after 4-week culture. The buds were then transferred onto shoot formation medium containing 1.0 mg dm⁻³ BA, 0.1 mg dm⁻³ gibberellic acid and 2.0 mg dm⁻³ silver nitrate. The addition of AgNO₃ enhanced the frequency of the shoot formation from 61.3 to 87.6 %. Root induction medium was half-strength MS medium with 0.75 mg dm⁻³ indolebutyric acid and 0.02 mg dm⁻³ BA. The average root frequency was 84.3 %. The regenerated plantlets with healthy roots grew successfully when transferred to soil. Using this system we obtained over 10 regenerated plantlets from one explant.     

In vitro plant regeneration from leaf explants of Ophiorrhiza japonica

An efficient in vitro plant regeneration system from leaves of Ophiorrhiza japonica Blume was established for the first time. Callus formation rate was more than 90.4 % from leaf segments on Murashige and Skoog (MS) supplemented with either α-naphthaleneacetic acid (NAA) alone or in combination with 6-benzyladenine (BA). The highest shoot regeneration (78.9 %) was achieved on MS medium containing 2.0 mg dm⁻³ BA and 0.2 mg dm⁻³ NAA, with an average of 9.4 shoots developed per leaf segment. Shoot regeneration was also improved when the leaf explants were cultured in MS basal medium supplemented with 0.5 % (m/v) polyvinylpyrrolidone (PVP). The leaf explants from seedlings with age of about 18–27 d showed the highest shoot regeneration. The regenerated shoots were rooted on half-strength basal MS medium supplemented with 0.5 mg dm⁻³ indole-3-butyric acid (IBA), which averagely produced 24.8 roots per shoot. The plantlets were transferred to soil, where 100 % survived after 1 month of acclimatization.     

High frequency <Emphasis Type="Italic">in vitro</Emphasis> propagation of <Emphasis Type="Italic">Holarrhena antidysenterica</Emphasis> from nodal buds of mature tree

An in vitro method for propagation of Holarrhena antidysenterica Wall. has been developed using nodal explants from mature trees growing in the field. Irrespective of concentrations and combinations of growth regulators used, the axillary and terminal buds sprouted and elongated when inoculated on Murashige and Skoog (MS) medium. The highest numbers of shoots were formed when sprouted shoots were subcultured from MS basal medium onto MS medium containing 2 mg dm⁻³ N⁶-benzyladenine (BA) and 0.5 mg dm⁻³ α-naphthalene acetic acid (NAA). The shoot number further increased upon subculture on MS medium containing 0.5 mg dm⁻³ BA. By repeated sub-culturing of shoots derived from nodal axillary buds, a high frequency multiplication rate was established. The elongated shoots were excised and rooted in auxin free MS basal medium. Ex vitro rooting of in vitro formed shoots was achieved upon dipping the microshoots for 2 min in 2 mg dm⁻³ of indole-3-butyric acid solution. Successful field establishment and high (80–90 %) survival of plants was observed.     

An efficient in vitro propagation of Aristolochia indica

A rapid and efficient in vitro plant regeneration method was developed for Aristolochia indica. Multiple shoot formation was induced from shoot tip and nodal explants on Murashige and Skoog (MS) medium with 1 – 6 mg dm⁻³ 2-isopentenyl-adenine (2-iP) or 1 – 4 mg dm⁻³ 6-benzyladenine (BA). Maximum number of shoots were induced with 5 mg dm⁻³ 2-iP alone (about 12 – 14 shoots). Shoot differentiation occurred directly from the leaf bases as well as from the internodes when cultured on 1 – 4 mg dm⁻³ BA and 0.8 – 2 mg dm⁻³ α-naphthaleneacetic acid (NAA) containing medium. Regeneration from the callus occurred when the calli initiated on MS medium containing 0.6 – 4 mg dm⁻³ NAA in combination with 0.8 – 3 mg dm⁻³ BA were transferred to 1 – 6 mg dm⁻³ BA alone containing medium. Elongated shoots were separated and rooted in MS medium containing 1 mg dm⁻³ indole-3-butyric acid. These were then transferred to soil after gradual acclimatization.     

In vitro regeneration of Alstroemeria cv. ‘Yellow King’ by direct organogenesis

The common techniques for the in vitro production of Alstroemeria plants are based on rhizomes as explants, which have low multiplication rates and a high risk of carrying viral diseases. To overcome these problems, we developed a protocol for the in vitro regeneration of Alstroemeria cv.‘Yellow King’, by testing for shoot induction several explant sources (leaf, stem apices, rhizomes and immature inflorescence apices), temperature and light/dark regimes, hormone and salt concentrations. For shoot multiplication and rooting, several hormone concentrations were tested. We found that only the young floral apices produced adventitious shoots by direct organogenesis. The highest shoot induction rate (10.4 shoots per explant) was obtained by incubation in the dark for 15 days at 8 °C followed by 15 days at 25 °C and a 16-h/8-h light/dark regime, on a Murashige and Skoog (1962) liquid medium at 50% of the salt concentration, supplemented with 2.5 mg l⁻¹ KIN, 1.5 mg l⁻¹ BA and 1.0 mg l⁻¹ NAA, using a piece filter paper to support the explant. The highest shoot multiplication rate (9 shoots per explant) was obtained on a liquid MS medium at full strength supplemented only with BA at 1.0 mg l⁻¹. In vitro rooting of shoots was induced also on a liquid MS medium, either with or without plant hormones.     

In vitro clonal propagation of Nyctanthes arbor-tristis

Rapid shoot multiplication of Nyctanthes arbor-tristis L. was achieved from axillary meristems on Murashige and Skoog (MS) basal medium supplemented with 1.0–1.5 mg dm⁻³ 6-benzylaminopurine (BA), 50 mg dm⁻³ adenine sulfate (Ads) and 3 % (m/v) sucrose. Inclusion of indole-3-acetic acid (IAA) in the culture medium along with BA + Ads promoted a higher rate of shoot multiplication. Maximum mean number of microshoots per explant (6.65) was achieved on the MS medium supplemented with 1.5 mg dm⁻³ BA, 50 mg dm⁻³ Ads and 0.1 mg dm⁻³ IAA after 4 weeks of culture. The elongated shoots rooted within 13 to 14 d on half-strength MS medium supplemented with either indole-3-butyric acid (IBA), IAA or 1-naphthaleneacetic acid (NAA) with 2 % sucrose. Maximum percentage of rooting was obtained on medium having 0.25 mg dm⁻³ IBA and 0.1 mg dm⁻³ IAA. About 70 % of the rooted plantlets survived in the greenhouse. The in vitro raised plants were grown normally in the field.     

Micropropagation of <Emphasis Type="Italic">Scabiosa caucasica</Emphasis> Bieb. Cv. Caucasica blue

Summary Micropropagation of Scabiosa caucasica cv. Caucasica Blue was achieved by culturing, separating axillary and adventitious shoots, or node sectioning on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA). The highest frequency of adventitious shoots regenerated from nodal or internodal explants and leaf blade (with or without petiole) appeared to occur on MS medium with 4.4 and 18 μM BA, respectively. Addition of 0.19 or 1.9 μM α-naphthaleneacetic acid to the BA-containing medium promoted callus formation and reduced shoot organogenesis. During micropropagation, shoot nodal explants derived from in vitro shoots cultured on MS medium supplemented with 4.4 μM BA yielded 8.9 shoots per explant within 40 d after culture initiation.     

Thidiazuron-induced <Emphasis Type="Italic">in vitro</Emphasis> shoot organogenesis of the medicinal plant <Emphasis Type="Italic">Arnebia euchroma</Emphasis> (Royle) Johnst

Summary An efficient in vitro propagation system was developed for Arnebia euchroma, an important Chinese traditional medicinal plant. The present study utilized thidiazuron (TDZ) for the induction of shoot organogenesis on cotyledon and hypocotyl explants. The maximal number of shoots was obtained on the modified Linsmaier and Skoog (LS) medium supplemented with 1.0 mgl⁻¹ (4.5 μM) TDZ for 12d on cotyledon explants (8.6 shoots per cotyledon explant). Other cytokinins (kinetin and 6-benzyladenine) and auxin (α-naphthaleneacetic acid) were not efficient in inducing regeneration on cotyledon explants. Browning of the basal portion of the subcultured shoots could be significantly reduced when they were cultured on the modified LS medium supplemented with 100 mgl⁻¹ (33.3 μM) polyvinylpyrrolidone. Well-developed shoots formed roots on the same medium containing 1.0 mgl⁻¹ (4.9 μM) indole-3-butyric acid. The efficient regeneration protocol reported here provides an important means of micropropagation of this plant. Furthermore, this protocol is essential to future genetic improvement of plants via transformation protocols.     

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.     

Production of adventitious shoots and plantlets from the hypocotyl explants of Sesbania rostrata (Bremek & obrem)

Summary Adventitious shoots were induced from the hypocotyl explants derived from 12–15-d-old seedlings of Sesbania rostrata on Nitsch's medium (Nitsch, 1969) supplemented with 1 mgl⁻¹ (4.4 μM), of N⁶-benzylademine (BA). A maximum of 5.9±3.4 shoots per explant in 100% of cultures were obtained. The BA treatment for different time durations (1, 3, 5, 7, 10, 17, 21, or 30 d) exhibited significant variation in the caulogenic potential of the explants. BA treatment for 10–17 d proved optimum for the response. Although at all concentrations of kinetin the explants developed multiple shoots, they were malformed. Sucrose at 3% exhibited the development of the maximum of 3.5±0.9 shoots per explant with an average shoot length of 4.7±3.9 cm. Among the different carbon sources, i.e., fructose, galactose, maltose, mannose, and sucrose at 3% (w/v), sucrose supported the best caulogenic response. The role of various other factors (viz. size, orientation of explant, and seedling age) on the caulogenic response of the hypocotyl explants of S. rostrata were also studied. The shoot development in all cases was accompanied by the development of moderate to profuse callus at the basal cut end of the explant. The in vitro-regenerated shoots produced roots when transferred to half-strength MS medium (Murashige and Skoog, 1962) supplemented with 3% sucrose and 1 mgl⁻¹ (4.9 μM) indole-3-butyric acid (IBA). The developed plantlets were transferred to the field after an initial acclimatization period of 3–4 mo. Such transferred plants produced flowers and fruits in the field and exhibited the development of prominent and organized stem nodules.