In vitro shoot culture and microtuber induction in the steroid yam Dioscorea composita Hemsl

The individual effects of sucrose, plant growth regulators and basal salt media formulations were investigated on microtuber induction and development in shoot cultures of the steroid yam Dioscorea composita. Sucrose at 8% (w/v) was the single most significant medium constituent for microtuber induction. Of the four cytokinins tested, 6-benzyladenine at 1.25 and 2.5 μM showed strong inhibitory effects on microtuber induction. By contrast, the auxins α-naphthaleneacetic acid and indole-3-butyric acid at 5.0 μM showed striking promotive effects on microtuber induction and growth. In the presence of either one of these auxins at 5.0 μM shoot cultures produced microtubers weighing 300–400 mg fresh weight whilst kinetin, 6-(γ,γ-dimethylallylamino)-purine, 6-benzyladenine and abscisic acid failed to promote microtuber growth (microtubers weighed generally <200 mg). Media formulations Lloyd and MacCown and White supported the lowest frequencies of microtuber induction when kinetin was present at 2.5 μM. Anderson Rhododendron was as effective as Murashige and Skoog overall in promoting both microtuber induction and growth. When removed from cultures and planted in sterilized moist sand, microtubers sprouted readily (60–87% within 2 weeks) and produced vigorous shoot growth and after 5–7 months minitubers of sizes (30–80 g) suitable for direct field planting. This revised version was published online in June 2006 with corrections to the Cover Date.     

Miscanthus×giganteus plant regeneration: effect of callus types,ages and culture methods on regeneration competence

The perennial rhizomatous grass, Miscanthus×giganteus is an ideal biomass crop due to its rapid vegetative growth and high biomass yield potential. As a naturally occurring sterile hybrid, M. ×giganteus must be propagated vegetatively by mechanically divided rhizomes or from micropropagated plantlets. Plant regeneration through somatic embryogenesis is a viable approach to achieve large‐scale production of plantlets in tissue culture. Effect of the callus types, ages and culture methods on the regeneration competence was studied to improve regeneration efficiency and shorten the period of tissue culture in M. ×giganteus. Shoot‐forming calli having a yellow or white compact callus with light‐green shoot‐like structures showed the highest regeneration frequency. Percentage of shoot‐forming callus induction from immature inflorescence explants was 41% on callus induction medium containing 13.6 μM 2,4‐d and 0.44 μM benzyladenine (BA). The use of a regeneration medium containing 1.3 μM NAA and 22 μM BA was effective at shortening the incubation period required for plantlet regeneration, with 69% of total regenerated plantlets obtained within 1 month of incubation on regeneration medium. Embryogenic‐like callus morphotype could maintain regeneration competency for up to 1 year as suspension cultures. Field grown regenerated plants showed normal phenotypic development with DNA content and plant heights comparable to rhizome propagated plants. Winter survival rates of the regenerated plants planted in 2006 and 2007 at the University of Illinois South Farm, Urbana‐Champaign, Illinois, were 78% and 56%, respectively.     

Somatic embryogenesis from mature <Emphasis Type="Italic">Bambusa balcooa</Emphasis> Roxburgh as basis for mass production of elite forestry bamboos

A reliable protocol for mass propagation via somatic embryogenesis in mature bamboos has been established using pseudospikelets of Bambusa balcooa. Fourty percent of the explants gave rise to multiple regenerants within 4 months. This conversion rate is sufficiently high to use the process in commercial mass production. Further, shoot apical meristems can also be used as primary explants without lost of efficiency. Regenerated plants were uniform and identical to the mother plant and to plants obtained by axillary branching with respect to growth characteristics and morphology. Furthermore, epigenetic changes could not be detected by Methylation Sensitive AFLP (MSAP). During the complete process no changes in ploidy level could be observed. The process allows for a cost reduction for this tropical bamboo for forestry of up to 57% compared to micropropagation via axillary branching. For the first time, a reliable process based on somatic embryogenesis has been developed that is well suited for commercial micropropagation of elite mature bamboos.     

Mist trickling bioreactor for <Emphasis Type="Italic">Centaurium erythraea</Emphasis> Rafn growth of shoots and production of secoiridoids

Shoots of Centaurium erythraea Rafn were cultivated in 5 l mist trickling bioreactor for 21 and 28 days increasing their dry weight from 0.54 g to 13.7 g and 18.3 g, respectively. About 6880 shoots from 223 initial shoot-tips in 21-day bioreactor producing cycle were produced. The shoots could be successfully rooted and transferred to soil. Secoiridoid accumulation (expressed as a sum of gentiopicroside, sweroside and swertiamarin) in shoots after 21 days of culture reached about 303 mg l⁻¹.     

Efficient <Emphasis Type="Italic">in vitro</Emphasis> bulblet regeneration from immature embryos of endangered <Emphasis Type="Italic">Sternbergia fischeriana</Emphasis>

Sternbergia fischeriana is an endangered geophyte and therefore in vitro micropropagation of this plant will have great importance for germplasm conservation and commercial production. Bulb scale and immature embryo explants of S. fischeriana were cultured on different nutrient media supplemented with various concentrations of plant growth regulators. Immature embryos produced higher number of bulblets than bulb scales. Large numbers of bulblets were regenerated (over 80 bulblets/explants) from immature embryos on Murashige and Skoog (MS) medium supplemented with 4 mg l^–1 6-benzylaminopurine (BA) and 0.25 mg l^–1 -naphthaleneacetic (NAA) or 2 mg l^–12,4-dichlorophenoxyacetic acid (2,4-D) after 14 months of culture initiation. Regenerated bulblets were kept at 5 °C for 5 weeks and then transplanted to a potting mixture.     

Micropropagation of <Emphasis Type="Italic">Kalopanax pictus</Emphasis> tree via somatic embryogenesis

Summary Kalopanax pictus (Thunb.) Nakai is a tall tree, and its wood has been used in making furniture, while its stem bark is used for medicinal purposes. Here, we report on the micropropagation of Kalopanax pictus via somatic embryogenesis. Embryogenic callus was induced from immature zygotic embryos. The frequency embryogenic callus induction is influenced by days of seed harvest. Callus formation was primarily observed along the radicle tips of zygotic embryos incubated on Murashige and Skoog (MS) medium with 4.4 μM 2,4-dichlorophenoxyacctic acid (2,4-D). Somatic embryogenesis was observed following transfer of embryogenic callus to MS medium lacking 2,4-D. Somatic embryos at the cotyledonary stage were obtained after 6 wk following culture. Frequency of conversion of somatic embryos into plantlets was low (35%) on a hormone-free MS basal medium, but it increased to 61% when the medium was supplemented with 0.05% charcoal. Gibberellic acid (GA₃) treatment markedly enhanced the germination frequency of embryos up to 83%. All plantlets obtained showed 98% survival on moist peat soil (TKS2) artificial soil matrix. About 30 000 Kalopanax pictus plants were propagated via somatic embryogenesis and grown to 3-yr-old plants. These results indicate that production of woody medicinal Kalopanax pictus plantlets through somatic embryogenesis can be practically applicable for propagation.     

The Influence of Radiation Quality on the in vitro Rooting and Nutrient Concentrations of Peach Rootstock

The effect of radiation quality (350 – 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.     

In vitro Growth and Shoot Multiplication of Achras zapota in a Controlled Carbon Dioxide Environment

The culture vessels with multiplying shoots of Achras zapota L. on Schenk and Hildebrandt (SH) medium containing 8.88 M 6-benzylaminopurine (BAP) with or without sucrose were kept under varied CO₂ concentrations ranging from 0.6 to 40.0 g m^–3 using different concentrations of sodium bicarbonate (NaHCO₃), sodium carbonate (Na₂CO₃), potassium bicarbonate (KHCO₃), and potassium carbonate (K₂CO₃) in small acrylic chambers. Complete absence of carbon source caused death of shoots within 20 d. Under elevated concentrations of CO₂ (10.0 and 40.0 g m^–3) the shoots grew photoautotrophically on sucrose-free medium. The growth of cultures was better at 40.0 g (CO₂) m^–3 than on 3.0 % sucrose under ambient air of growth room. However, the best response was obtained at 10.0 g (CO₂) m^–3 and 3.0 % sucrose where maximum number of shoots, shoot length, fresh and dry mass, total number of leaves and leaf area was observed.     

Genetic stability of three economically important micropropagated banana (Musa spp.) cultivars of lower Indo-Gangetic plains, as assessed by RAPD and ISSR markers

An efficient micropropagation protocol produced large number of plants of the three elite banana (Musa spp.) cultivars Robusta (AAA), Giant Governor (AAA) and Martaman (AAB) from shoot tip meristem. The genetic relationships and fidelity among the cultivars and micropropagated plants as assessed by random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers, revealed three somaclonal variants from Robusta and three from Giant Governor. A total of 5330 RAPD and 2741 ISSR fragments were generated with 21 RAPD and 12 ISSR primers in micropropagated plants. The percentage of polymorphic loci by RAPD and ISSR were found to be 1.75, 5.08 in Robusta and 0.83, 5.0 in Giant Governor respectively. Among the two marker systems used, ISSR fingerprinting detected more polymorphism than RAPD in Robusta and Giant Governor with most of the primers showing similar fingerprinting profile, whereas Martaman revealed complete genetic stability.