Volume Information [PDF]
Genetic Engineering and Transgenesis
Chapter 1 Genetic engineering in floricultural plants. FJL Aragão, LPB Cid, Brazil (pp 1-8)
There is considerable interest in the introduction of agronomically useful traits into ornamental species. Rapid progress in plant molecular and cellular biology has great potential to contribute to the breeding of novel floricultural plants for the market, utilizing recombinant DNA technology. Molecular genetic manipulation for applied purposes is only possible with the development of an efficient protocol for transformation. The genetic manipulation process is dependent on the ability of plant tissue to produce totipotent cells that can be regenerated into a completely viable plant. The use of genetic engineering to incorporate useful genes into elite breeding lines is dependent on the development of tissue culture techniques. The majority of transformation protocols used in ornamental species is based on gene transfer mediated by Agrobacterium and particle bombardment (biolistic process). In this chapter, we discuss the technologies developed to regenerate and genetically modify ornamental plants in order to introduce new traits, such as color, longevity, and scent in flowers and architecture, acclimatization efficiency, and tolerance to biotic and abiotic stress in vegetative organs.
2) Selector and marker genes, and vectors
Chapter 2 Marker and selector genes for plant transformation. L Tian, M Jordan, B Miki, Canada (pp 9-20)
No single selectable marker can meet all research purposes, due to differences in transformation protocols, biological differences related to species and explant and the objective of the research. Various selectable markers have been developed for the generation of transgenic plants each with advantages and disadvantages. In additional to selectable markers, visible markers possess unique features and are an important companion to selectable markers for use in genetic transformation. The selectable and visible markers commonly used for plant transformation are described and assessed. Recently, new markers possessing novel features have been developed. Potential for wide usage of these markers in plant transformation is discussed. For selection effectiveness and efficiency it is important, and very often essential, to have appropriate levels of marker gene expression. Strategies to control marker gene expression are also reviewed.
Chapter 3 Development of tissue-specific promoters for plant transformation. PA Manavella, RL Chan, Argentina (pp 21-25)
Biotechnology contributes to the improvement of crops by introducing a single gene conferring a desired phenotype. To succeed in this process it is necessary to identify the gene able to confer the desired characteristic and a promoter region directing the expression of this gene in the adequate time and place. Each plant gene has its own promoter region, usually located upstream the coding sequences, presenting cis-acting elements responsible for tissue/organ specific expression as well as for induction/repression by external factors. Most recognition mechanisms are conserved in the whole plant kingdom, but significant differences have been observed between mono and dicot plants. Constitutive promoters are sequences that direct gene expression at a high level in the whole plant during all developmental stages. They have widely used for fundamental research as well as biotechnological tools, but their use leads to unnecessary metabolic expenses for the transformed plant. On the other hand, tissue/organ specific promoters have been described but expression directed by them is not enough strong to reach the desired acquired phenotype in the transformed plant. The use of artificial constructions combining specific cis-acting elements or entire weak promoters with enhancers is proposed. Several techniques developed to test a promoter’s activity are presented. Finally, we discuss the possibility to obtain improved ornamental plants in the future by a combination of a suitable promoter with a coding sequence able to confer a desired phenotype. Changing petals color or obtaining a senescence delay became possible objectives.
Chapter 4 Marker gene removal from transgenic plants. L Tian, Canada (pp 26-29)
Marker gene removal from transgenic plants is an important component of plant genetic engineering and biotechnology. Marker elimination will remove potential environmental risks, consumer concerns, and technical barriers for plant genetic engineering. Different methods for marker elimination have been described. This article discusses the major technologies and approaches used for marker removal.
Chapter 5 Novel approaches to protein expression using plant virus expression vectors. KL Hefferon, USA (pp 30-40)
Plants present a rich source of biomass for the production of proteins in large quantities. Specifically, expression of foreign proteins by transient expression using plant viral expression vectors has several advantages over constitutive expression in transgenic plants. For example, proteins which are potentially toxic and cannot be expressed in transgenic plants can be expressed at high levels using plant virus-based expression vectors. In general, higher levels of foreign protein can be expressed by plant viruses. Furthermore, plant virus-based expression avoids many of the biosafety concerns surrounding transgenic plants. In the past, most approaches for the expression of foreign genes have focussed on either expression of the foreign protein as a fusion to a viral protein or from a duplicated subgenomic mRNA promoter. In this chapter, we examine the most recent strategies that have been developed to utilize plant virus-based expression systems for a multitude of purposes. This chapter covers ‘the deconstructed virus strategy’ versus the ‘full virus strategy’ of plant virus-based expression vectors. We go over various means by which conventional plant virus vectors can be improved and applications for both commercial uses and as a research tool. Finally, we cover the development of application of plant viral vectors in terms of large scale field trials.
3) Novel transformation techniques
Chapter 6 Development of in planta transformation methods using Agrobacterium tumefaciens. M Kojima, P Sparthana, JA Teixeira da Silva, M Nogawa, Japan (pp 41-48)
This chapter describes simple and efficient in planta transformation methods using Agrobacterium tumefaciens for buckwheat (Fagopyrum esculentum M.), mulberry (Morus alba L.), kenaf (Hibiscus cannabinus L.) and rice (Oryza sativa L.). In the methods, meristems of either apical (buckwheat, kenaf and rice) or axillary bud (mulberry and kenaf) of young plants (buckwheat, kenaf, and mulberry) or soaked seeds (rice) were inoculated by A. tumefaciens after being pricked with a needle. The inoculated plants were grown to maturation in pots under nonsterile conditions. Transformation was demonstrated by several lines of evidence obtained by using mostly the progenies of the T1 generation; phenotypic inheritance from T0 plants to the plants of the following generation, detection of transgene and its transmission to the following generation, rescue of plasmids composed of T-DNA of the binary vector and flanking plant genomic DNA, detection of β-glucuronidase activity in the transformants and resistance of seed germination of transformants to antibiotics (geneticin or hygromycin).
Chapter 7 Floral dip transformation of Chenopodium rubrum. J Veit, E Wagner, JTP Albrechtová, Germany (pp 49-53)
The development of a robust Agrobacterium-mediated transformation protocol for a recalcitrant species like Chenopodium rubrum requires the identification and optimization of the factors affecting transformation efficiency. We have demonstrated that C. rubrum can be transformed in a stable and heritable way using the floral-dip method and found that plant developmental stage and fitness after dipping were critical for successful transformation. The floral dip transformation system will increase the utility of the model plant C. rubrum. Further adaptation of this technique will provide a useful tool for the transfer of foreign genes into close relatives of C. rubrum such as spinach, sugarbeet and Chenopodium quinoa, all being agriculturally important crops.
Chapter 8 Dwarfing ornamental crops with the rolC gene. AG Smith, KE John, N Gardner, USA (pp 54-59)
The rolC gene is found on the RI plasmid of Agrobacterium rhizogenes. Plants expressing this gene have significant changes in phenotype, including reductions in height, apical dominance, internode length, and leaf size. These changes can be beneficial to plant breeders attempting to create novel, smaller versions of existing cultivars. The rolC gene has been introduced into several ornamental species, including Antirrhinum majus, Begonia tuberhybrida, Betula pendula, Chrysanthemum morifolium, Datura arborea, Datura sanguinea, Dianthus caryophyllus, Eustoma grandiflorum, Lilium longiflorum, Limonium otolepis x Limonium latifolium, Malus prunifolia, Osteopermum ecklonis, Pelargonium x domesticum, Petunia axillaris x (P. axillaris x P. hybrida)and Populus tremula x P. tremuloides. These species exhibited changes in morphological traits such as dwarfness, increased branching, increased flower number, and unique leaf morphology. These traits are heritable from one generation to another, and the degree of phenotypic change is affected by the amount of rolC produced under a specific promoter. The introduction of rolC into plant species is an effective way to produce dwarf plants and has potential for breeding unique ornamental cultivars.
Chapter 9 Fluorescent molecules in plant biotechnology. A Mercuri, L De Benedetti, S Bruna, T Schiva, S Alberti, Italy (pp 60-65)
Green Fluorescent Protein (GFP) from the jellyfish Aequorea victoria is a spontaneously fluorescent protein, that is widely used as a recombinant protein tag in vivo. A huge number of researchers have used GFP to label proteins, cells and organisms in a wide range of prokaryotic and eukaryotic species with the aim of investigating basic questions of cellular and developmental biology, neurobiology and ecology and of developing innovative biotech tools. A key reason for the invaluable usefulness of GFP as a biological marker is the fact that this protein does not require additional / external cofactors to generate fluorescence. The wild-type or modified GFP gene has been introduced with different tech-niques in many plant species (monocot and dicot). The introduction and expression of the gfp gene in ornamental genomes may allow to develop novel classes of flower colors. Furthermore, the ability of GFP to generate fluorescence in living material, and its detection in real time, would offer a novel method for the phenotypic monitoring of defined flower genotypes and to ascertain the diffusion and use of transgenic cultivars in the environment. However, the generation of fluorescent flowers remains by-and-large elusive. Major difficulty is the interference by background fluorescence and levels of GFP expression. These problems have been tackled and finally solved, thus obtaining green-fluorescent flowers.
Chapter 10 Novel approaches for Agrobacterium-mediated transformation of maize and ornamental grasses. SA Danilova, Russia, Jaime A. Teixeira da Silva, Japan, VV Kusnetsov, Russia (pp 66-69)
This brief review focuses the most important stages of Agrobacterium tumefaciens-mediated cereal transformation. Simple and efficient approaches for improved transformation are suggested. For Agrobacterium activation, we recommend the use of an extract of sterile tobacco plants instead of acetosyringone. At the stage of A. tumefaciens co-culture with plant explants, a long-term contact of explants with bacteria evenly distributed above the agar-solidified nutrient medium (agrobacterial monolayer) is important. Furthermore, to stimulate plant regeneration from cereal calluses, we suggest the application of the antibiotic cefotaxime at 50-150 mg/l. Applicability of these approaches for transformation of ornamental grasses is demonstrated.
4) Transgene expression, structure and silencing
Chapter 11 Transgene expression and silencing in plants. MFS Vaslin, Brazil (pp 70-76)
The capacity of produce transgenic plants posed a revolution in modern plant biology. The ability to transform crops with genes from any other organism opens up the entire community of life as the source for new genes for a crop. Reporter genes and chemically induced genes are opening new ways to see and understand gene function. Although RNA silencing is a relatively recent topic of research, the mechanisms are now becoming clear and there is some indication of its biological roles. The discovery of RNA silencing has completely changed our view of RNA as a regulatory molecule in eukaryotic cells and it is likely that this view will continue to evolve as further discoveries emerge about the diversity of silencing mechanisms.
Chapter 12 Conditional gene expression in plants. MD Curtis, U Grossniklaus, Switzerland (pp 77-87)
The precise timing and control of gene expression provides a mechanism by which plants have evolved developmentally and physiologically to cope with diverse environments and stressful conditions. The misexpression of endogenous or exogenous genes in plants leads to a better understanding of gene function and ultimately aids progress towards the development of new improved varieties. Advancement in inducible gene expression technologies facilitates more precise functional analyses, revealing additional roles for genes that act at multiple stages in the plant life cycle, and allowing the conditional complementation of genetic mutations at different stages in development. Conditional expression systems in agriculture may also increase public acceptance of genetically modified organisms and have already been used to generate marker-free transgenic plant lines. As more systems suitable for field application are developed, the conditional expression of genes in agriculture will allow traits to be modulated, or even reversed, providing flexibility in the production of future generations of crop plants.
Chapter 13 Epigenetic lessons from transgenic plants. IL Ingelbrecht, Nigeria/UK, TE Mirkov, USA, AG Dixon, A Menkir, UK (pp 88-97)
Transgenic plant studies have lead to the breakthrough discovery of RNA silencing as a conserved mechanism for gene regulation across kingdoms. Recent molecular genetic studies have revealed a major role for RNA silencing in the formation of silent chromatin, characterized by histone modifications and dense DNA methylation. These epigenetic marks ensure stable, yet potentially reversible, transmission of the silent state of genetic elements such as transgenes and transposable elements through multiple cell divisions, and in some cases, through successive generations. It is now recognized that epigenetic control mechanisms play a fundamental role in preserving the integrity of the genome against invasive parasitic nucleic acid elements such as viruses and transposons. It is also becoming clear that epigenetic processes are of major evolutionary significance in plants by providing plasticity to the genome to adjust to environmental changes and by stabilizing the genome after polyploidization events. RNA silencing is a powerful research tool to elucidate gene function in reverse genetics studies and has been applied in the production of virus resistant crops. An enhanced understanding of epigenetic processes is therefore not only of academic interest but will also provide new tools and techniques for plant scientists involved in conventional and biotechnology-based horticultural and agricultural crop improvement.
Chapter 14 Phenotype of the transgene in plants: expression and silencing. T Hamada, H Kodama, Japan (pp 98-107)
When we overexpress the transgene in plants, we encounter two completely different phenomena, namely, successful expression and silencing of the transgene. In the first half of this paper, we introduce several strategies for a high-level expression of the transgene. In the latter half we discuss another aspect of the transgene’s fate, i.e., cosuppression. The RNA interference (RNAi) pathway seems to account for the molecular basis of cosuppression. The presence of siRNA, a key molecule of the RNAi pathway, is an indication of plants displaying cosuppression. However, its presence does not always corresponded to the incidence of RNA silencing, suggesting the presence of regulatory mechanisms involved in the action of siRNA, especially in cosuppression between transgenes and the corresponding plant endogenous genes. Elucidation of the molecular bases of cosuppression facilitates the development of feasible strategies for boosting the accumulation of the recombinant proteins of interest by evading cosuppression.
Chapter 15 Gene expression studies in Arabidopsis thaliana – a network perspective. ASN Seshasayee, UK, L Aravind, MM Babu, USA (pp 108-116)
Control at the transcriptional level is the most fundamental mode of regulation of gene expression. Such control can be most effectively studied by monitoring expression patterns of genes in a genome wide fashion using DNA microarrays. In the first part of this chapter, we review some of the gene expression studies, covering tiling arrays and cDNA arrays, of the model flowering plant Arabidopsis thaliana. Following this, we focus on describingdifferent computational methods that one can use to analyze these large-scale gene expression datasets. In this section, after briefly introducing the techniques to cluster genes based on the similarity in expression profiles, we describe a powerful way to analyze this data, which is to study them as networks. Along these lines, we introduce some basic concepts to analyze these networks, describe the topology of simple relevance networks and first-order conditional independence networks. Furthermore, we also describe methods to derive functional modules from these networks. In conclusion, we explain how these approaches have been applied to gene expression datasets for Arabidopsis thaliana and hope to motivate the reader to think about how the data from plant genomics remains a fertile ground for further studies along similar lines.
Chapter 16 Retransformation of APETALA1 (AP1) early-flowering citrus plants as a strategy to rapidly evaluate transgenes addressing fruit quality traits. M Cervera, A Navarro, L Navarro, L Peña, Spain (pp 117-123)
Although recovery of transgenic plants expressing multiple transgenes can be of great interest for basic and applied plant sciences, integration of several transgenes in a specific genotype is not always easy and can compromise the potential of genetic transformation. Different strategies have been developed to face this problem, but advantages and disadvantages are present for all of them. In citrus, the existence of a long juvenile phase is one of the main obstacles for genetic improvement. Genetic transformation might circumvent it by using in breeding programs APETALA1 (AP1) transgenic lines, which show precocious flowering and short juvenile periods. By successive rounds of transformation (retransformation) it should be feasible to integrate and express genes implicated in flowering and/or fruiting processes, thus reducing drastically the period elapsed till evaluation of these traits is performed. Here we demonstrate that regeneration of multi-transgenic plants in citrus could be possible by successive rounds of transformation. Advantages of using this strategy and obstacles encountered to develop the system in citrus are examined in this chapter.
Chapter 17 Protoplast transient expression systems and gene function analysis. T Xing, Canada, X-J Wang, China (pp 124-128)
A protoplast is a plant cell from which the cell wall has been removed by enzyme treatment. Many uses of protoplasts have been explored and described. Some arguments or concerns in using protoplasts in gene function studies have been raised, however, many advantages of the system have been realized in recent years in various physiological, biochemical, genetic, and molecular biological studies and protoplasts continue to be a useful material in these disciplines. We have established reliable methods to isolate viable protoplasts from tomato mesophyll cells. Here, we present and suggest how we use protoplast transient gene expression systems to study the function of genes that are involved in plant defence responses. We specifically studied activation events downstream of a mitogen-activated protein kinase kinase (MAPKK), tMEK2, in tomato. Of particular interest is TAB2, a nucleoside diphosphate protein kinase (NDPK). Transient gene expression analysis in tomato protoplasts indicated that TAB2 gene was activated by tMEK2MUT. This activation was inhibited by co-expression of Arabidopsis dual-specificity protein tyrosine phosphatase (DsPTP1). ER5, a wound-inducible gene, was activated by tMEK2MUT and the activation was also inhibited by DsPTP1. It is important that these findings are confirmed by functional analysis following analysis in transient protoplast gene expression systems in an attempt to develop novel strategies to protect plant health and increase productivity.
Chapter 18 A cost-effective method for extracting siRNAs from transgenic plants. CW Li, Y Zhou, China (pp 129-132)
Small interfering RNAs (siRNAs) are the proven hallmark in silencing genes in a sequence-specific manner, and bear great potential in basic and applied research in biological sciences. Transgenic plants have been shown to have the potential as bioreactors in producing siRNAs functional in vivo and in vitro. For cost-effective and large-scale preparation of plant-derived siRNAs, a new, simple and effective method for the extraction from plant samples was devised with much reduced usage of either commercial or self-prepared extraction buffers. The method has a recovery rate as high as 57.3%, and the siRNA content in leaves of transgenic plants was estimated to be 5.5 μg per g of fresh weight. Therefore, this technique can effectively harvest siRNAs from transgenic plants that are cheap sources for siRNA production.
5) Applications and case studies of GMOs and GMPs
Chapter 19 Application and commercialization of transgenic ornamental plants. Y Yalçin-Mendi, N Buzkan, C Dölekoğlu, Turkey (pp 133-139)
The global flower industry thrives on novelty. Genetic engineering is providing a valuable means of expanding the floriculture gene pool so promoting the generation of new commercial varieties. There has been extensive research on the genetic transformation of different flowering plant species, and many ornamental species have now been sucessfully transformed, including those which are most important commercially. To date, more than 30 ornamental species have been transformed, including anthurium, begonia, carnation, chrysanthemum, cyclamen, datura, daylily, gentian, gerbera, gladiolus, hyacinth, iris, lily, lisianthus, orchid, pelargonium, petunia, poinsettia, rose, snapdragon and torenia (Deroles et al., 2002) New ornamental plant varieties are being created by breeders in response to consumer demand for new products. In general terms engineered traits are valuable to either the consumer or the producer. At present only consumer traits appear able to provide a return capable of supporting what is still a relatively expensive molecular breeding tool. Commercialisation of genetically engineered flowers is currently confined to novel coloured carnations. The production of novel flower colour has been the first success story in floriculture genetic engineering. However, further products are expected given the level of activity in the field. Other traits that have received attention include floral scent, floral and plant morphology, senescence of flowers both on the plant and post-harvest and disease resistance. To date, there are only a few ornamental genetically modified (GM) products in development and only one, a carnation genetically modified for flower colour, in the marketplace. There are approximately 8 ha of transgenic carnation in production worldwide, largely in South America. The other breeding programs on colour modification or alteration of plant architecture and height remain focusses on rose, gerbera and various pot plant species.
Chapter 20 Chrysanthemum biotechnology. H Shinoyama, Japan, N Anderson, USA, B-C Wang, China, H Furuta, A Mochizuki, Y Numura, Japan, R Singh, Canada, SK Datta, India, JA Teixeira da Silva, Japan (pp 140-163)
Chrysanthemum will remain an important global floricultural crop leader due to its extensive range of plant and flower colours, shape and form. Recent studies have demonstrated genotype-independent phenotypic plasticity of this ornamental crop, making it a suitable candidate as a floricultural model plant for in vitro studies on development and transformation. Significant findings in in vitro regeneration from thin cell layers and biotechnological breeding protocols involving somatic embryogenesis, intergeneric somatic hybridization, mutation/classical breeding, and genetic transformation demonstrate to the reader significant research in understanding the dynamic processes underlying growth, development, and flower induction of this plant. Although there is now a trend to use ion beams and genetic transformation to primarily induce novel flower characters, classical mutation breeding (using physical and chemical mutagens) remains an important source of variation. Protoplast electrofusion has been used to generate intergeneric, rust-resistant hybrids with wormwood which, together with the successful introduction of several insect, virus/viroid, and fungal resistance genes in a wide range of cultivars, will serve as a model plant to overcome many pest-related problems plaguing ornamentals in the global floricultural industry. Preliminary studies also indicate that, due to the capacity of the plant to withstand great stresses in and ex vitro, chrysanthemums might very well be suitable candidates for ornamental phytoremediation. Well-studied, established regeneration and transformation protocols will undoubtedly allow for rapid advances in the biotechnology of this jewel plant.
Chapter 21 Genetic engineering of ethylene production and perception in carnation and chrysanthemum. S Satoh, Y Kosugi, Y Iwazaki, T Narumi, T Kinouchi, Japan (pp 164-171)
Ethylene is a primary plant hormone involved in the senescence of carnation flowers. Inhibition of the synthesis or action of ethylene delays the onset of senescence symptoms and increases the vase life of the flowers. Leaves of cut chrysanthemum of some cultivars frequently become yellow, sometimes prior to the onset of flower senescence. The leaf yellowing is induced by the action of exogenous ethylene. Generation of transgenic plants with suppressed production or action of ethylene is an excellent way to lengthen the longevity of these ornamental plants. This chapter reviews our recent results on generation and characterization of carnations with reduced ethylene production and chrysanthemum with reduced sensitivity to ethylene.
Chapter 22 Production of transgenic plants via Agrobacterium-mediated transformation in Liliaceous ornamentals. M Nakano, S Mori, S Suzuki, Y Hoshi, H Kobayashi, Japan (pp 172-183)
Studies on the Agrobacterium-mediated production of transgenic plants in several Liliaceous ornamentals, Lilium spp., Agapanthus spp., Muscari armeniacum and Tricyrtis hirta are described. Different strains of A. tumefaciens were used, all of which harbored the binary vector carrying the neomycin phosphotransferase II (NPTII) gene, the intron-containing β-glucuronidase (GUS) gene, and the hygromycin phospho-transferase (HTP) gene in the T-DNA region. Utilization of organogenic or embryogenic calluses as a target material for transformation and acetosyringone (AS) treatment during inoculation and/or co-cultivation with Agrobacterium were found to be critical for successful production of transgenic plants in Liliaceous ornamentals. Following transfer of co-cultivated organogenic or embryogenic calluses onto hygromycin-containing media, several hygromycin-resistant (Hygr) tissues were obtained, and complete plants were subsequently developed from these tissues. Most of the plants were verified to be transgenic plants by GUS histochemical assay and PCR analysis. For Lilium ‘Acapulco’, A. praecox ssp. orientalis ‘Royal Purple Select’ and M. armeniacum ‘Blue Pearl’, Southern blot or inverse PCR analysis revealed the integration of 1-5 copies of the transgene into the genome of transgenic plants, but most of them had 1 or 2 copies. Agrobacterium-mediated transformation systems thus established may be useful as a tool for molecular breeding as well as molecular biological studies.
Chapter 23 Genetic transformation of two species of orchid. Y Li, X Nie, China, JA Teixeira da Silva, Japan, S Men, C Wei, China (pp 184-192)
Orchids are distinctive flowering plants, which represent the largest family of ornamental plants among monocotyledons and occupy a wide range of ecological habitats and exhibit highly specialized morphological, structural, and physiological characteristics. The family Orchidaceae includes a number of commercially important species that are grown for cut flowers and potted plants. Vegetative propagation slows down the breeding process of orchids, and modern genetic engineering techniques provide an effective alternative. Genetic engineering technology has been used to create new traits and shorten breeding time to improve existing successful cultivars in other crops. However, our understanding of floral development in orchids at the molecular level is just beginning. Until recently, transgenic orchid plants have been reported for only a few orchid genera. The first transgenic orchid plant was reported in Dendrobium and was generated using biolistic bombardment. In all the above investigations, the transformation efficiency was relatively low. In this chapter the high efficiency of genetic transformation of two orchid species is introduced.
Chapter 24 Oncidium tissue culture, transgenics and biotechnology. M-T Chan, Sanjaya, Taiwan, JA Teixeira da Silva, Japan (pp 193-198)
Oncidium is a commercially important orchid, and considerable research efforts of numerous biotechnologies have been deployed in the past few years to improve its mass propagation, gene transformation and disease resistance. The ability to regenerate plants from cultured cells, tissues or organs provides an efficient tool for plant transformation. Protocorm like bodies (PLBs) were the most convenient target tissue in different gene transformation systems including Agrobacterium-mediated and microprojectile bombardment. A range of available molecular and biochemical tools to confirm transgene integration and expression made the outcome of such experiments more understandable. The integrated approaches of genetic engineering in Oncidium have been of great value because of its commercial value. Indeed, more recently Oncidium is the subject of new areas of research including functional genomics, proteomics, and metabolomics. For the successful application of these new approaches to improve traits in Oncidium a reliable and reproducible transformation technique is essential. This chapter attempts to highlight Oncidium tissue culture, with an emphasis on gene transformation and need for biotechnological applications, and the potential areas of research.
Chapter 25 Optimization of parameters for delivery of transgenes to turfgrass cells. C Basu, AP Kausch, JM Chandlee, USA (pp 199-203)
Parameters for use of the PDS-1000/He (Bio-Rad, USA) particle delivery system were optimized for routine delivery of transgenes into turfgrass cells in an attempt to standardize methods for routine and efficient genetic transformation of turfgrass species (creeping bentgrass, cv. Penn A4). Among various callus types produced on callus induction medium, embryogenic callus was identified using electron microscopy. Suspension cultures of Penn A4 were bombarded using a ubiquitin rice promoter-GUS gene construct. Based on the number of ‘GUS hits’, the following conditions were determined to be optimal for transfer of foreign gene constructs into turfgrass cells: 1.0 mm gold, 7 ml DNA/ shot and 1100 psi rupture disc type. Transient GUS expression patterns in turfgrass suspension culture cells driven with three different promoters (PGEL1, ubiquitin rice-GUS and ubiquitin corn-GUS) were also evaluated. The ubiquitin rice promoter was determined to be an ideal promoter for driving high levels of foreign gene expression in turfgrass cells. This observed variation in reporter gene (GUS) expression provides important information regarding variability of promoter strengths and expression patterns that will be important when choosing a strong promoter for gene transfer experiments targeted for trait modification or enhancement in turfgrass.
Chapter 26 Transgenic plants for bioremediation. S Eapen, SF D’Souza, India (pp 204-208)
Phytoremediation – the potential of plants to extract, sequester and/or detoxify toxic metals and xenobiotics has evoked considerable interest among plant biotechnologists and environmental biologists in the last few years due to its environmentally compatible and aesthetically pleasing qualities. Plants, although having the inherent ability to take up toxic metals and metabolize organic pollutants, the development of transgenic plants will give an opportunity for the transfer of genes across species barriers, resulting in enhanced efficiency of metal accumulation and detoxification of xenobiotics. Genes involved in uptake, translocation and sequestration of metals can be transferred from hyperaccumulator plants or from other sources into candidate plants for development of transgenic plants with improved metal accumulation. The detoxification of toxic organomercurial compounds and subsequent volatilization of elemental mercury by transgenic plants is an example of such a well conceived plant engineering strategy. Transfer of genes associated with xenobiotic metabolism from microbes/mammals to plants may also help in processing xenobiotics as in the case of transgenic plants with the mammalian cytochrome p4502E1 gene, which has resulted in plants metabolizing a number of xenobiotics such as trichloroethylene (TCE) and ethylene dibromide. As our understanding of the genetic basis of metal and xenobiotic metabolism improves, coupled with development of genome sequencing projects and analytical techniques, it will be possible to develop novel transgenic plants for environmental clean up.
Chapter 27 Tropane alkaloids in plants. Genetic engineering of tropane alkaloid biosynthesis. J Palazón, E Moyano, M Bonfill, RM Cusidó, MT Piñol, Spain (pp 209-221)
Tropane alkaloids occur mainly in the Solanaceae and include the anticholinergic drugs hyoscyamine and scopolamine, whose biosynthesis takes place in the plant root. Some of these Solanaceae plants have developed a wide diversity of morphological traits that make them suitable for ornamental purposes, but their main use is as a source of both hyoscyamine and scopolamine. Since scopolamine is more valuable, there has been a long-standing interest in raising the scopolamine content of producing plants and their hairy root cultures. At present, two flux-limiting steps in the biosynthetic pathway for scopolamine have been demonstrated and the corresponding genes cloned, making the metabolic engineering of the pathway possible. The first step is the conversion of putrescine into N-methylputrescine, the reaction being catalysed by putrescine:SAM N-methyltrnsferase (PMT). This enzyme removes putrescine from the polyamine pool and drives the methylated compound exclusively toward tropane alkaloid production. The second limiting step is at the level of the enzyme hyoscyamine-6b-hidroxilase (H6H), which biotransforms hyoscyamine into the epoxide scopolamine. The pmt gene of Nicotiana tabacum under the control of the CaMV 35S promoter was introduced into the genome of two scopolamine-rich plant species, Datura metel and a Duboisia hybrid, together with the T-DNA of the Ri plasmid from Agrobacterium rhizogenes. The results obtained showed a different pattern from hyoscyamine and scopolamine biosynthesis control in the hairy root cultures belonging to both species. In Datura, the ectopic expression of the transgene 35S-pmt increased the biosynthesis of hyoscyamine and scopolamine, whereas in Duboisia, the overexpression of this transgene increased the levels of N-methylputrescine but the alkaloid production remained similar to that of the control roots. In contrast, overexpression of the 35S-h6h gene of Hyoscyamus niger in hairy root cultures of Duboisia hybrid and Hyoscyamus niger, besides enhancing the bioconversion of hyoscyamine into scopolamine, also increased the hyoscyamine production. Enhancement of scopolamine production in hairy root cultures producing mainly hyoscyamine has also been achieved using metabolic engineering. An important conclusion from all these experiments is that the identification and cloning of regulatory genes might eventually be more successful for improving production, as such genes might control larger sections of the pathway, if not its entirety.
Chapter 28 Tissue culture, cell culture and genetic transformation by wild type Agrobacterium rhizogenes in Mediterranean Helichrysum. A Giovannini, Italy (pp 222-226)
Helichrysum italicum and H. stoechas (family Asteraceae) are two spontaneous species of the Mediterranean region. The plants grow in arid soils, from the cliffs above the sea to the hills, where they flower from May to July. The bright yellow flower heads contain essential oils, tannins, caffeic acid and other useful substances. H. italicum and H. stoechas are used in folk medicine because of their antibacterial, antitoxic, diuretic and antiallergic properties; moreover they are appreciated as dried flowers. Tissue cultures from H. italicum and H. stoechas in vivo germinated seedlings were established. Micropropagation and rooting was achieved in basal Murashige and Skoog medium without any growth regulators. The organogenetic potential of leaf tissues was evaluated under light conditions, combined with different growth regulators concentrations. Shoot induction from leaf tissue was obtained in H. italicum on a medium supplemented with Zeatin and IAA. Callus was induced from micropropagated leaf tissues in a medium enriched with 2,4-D and Kinetin. Fast growing H. italicum cell cultures were established in liquid medium. An efficient protocol for hairy root induction using wild type Agrobacterium rhizogenes has been established for both H. italicum and H. stoechas. Hairy root-regenerated plants were recovered in H. stoechas. H. italicum cell and hairy root liquid cultures could be used for secondary metabolites production, besides H. stoechas hairy root-regenerated plants could be study to assess inflorescence antibacterial activity.
6) Risks of GMOs and GMPs
Chapter 29 The use of modern biotechnologies in ornamental plant growing and landscape horticulture. AM Kulikov, Russia (pp 227-231)
The leading role of scientific and technological progress in the economy of developed countries has become a truism. Moreover, and informational and other high technologies are generally believed to play an exceptional role in the economy of postindustrial or information society, which is regarded as the next stage of the development of the world civilization. This point of intersection between society's expectations and actual possibilities of science is where a serious conflict is brewing. Often the impetuous development of technology and rapid adoption of latest scientific achievements is not accompanied by well-grounded estimation of their medical, ecological, and social consequences. To date, the economic outcome of the practical implementation of scientific developments is given priority over the principles of safety dictating the necessity of long-term, comprehensive tests of all new technologies and products. Nevertheless, taking into account the rate at which scientific knowledge and technology are developing and the global effect of technologies on the society and environment, mankind will have to solve this problem. Here, we will estimate the risks entailed by the application of genetic engineering methods to floriculture and landscape horticulture.
Chapter 30 Engineered sterility for non-native plant invaders. AG Smith, NO Anderson, USA (pp 232-239)
Invasive species are a primary threat to biodiversity on the planet, second only to habitat destruction, and are one of the least reversible of all human impacts on the environment. An invasive plant is likely to spread to new areas or environments and develop self-sustaining populations, which then become disruptive to the ecosystem. Both native and non-native plants can be invasive, however this review focuses on non-native invaders because of their association with the introduction and cultivation of ornamental plants. The enthusiasm of growers and consumers for novel ornamental plants drives plant breeders and others to develop cultivars from non-native species. Several characters contribute to invasive potential, however a major determinant for many invasive plants is seed production. Plants that are sterile or cannot set seed have a greatly reduced invasive potential. Using biotechnology to introduce sterility genes into plants with invasive potential has wide applicability. The development of sterility genes and their introduction into ornamental plants with invasive potential can be used to produce non-invasive cultivars. Sterility genes may alter expression of specific genes and disrupt the development of reproductive organs or may ablate tissue essential to reproduction. An essential factor for the application of either strategy is that the aesthetic quality of the flower is preserved.
Chapter 31 Intellectual property on plant varieties. J Wegner, France (pp 240-243)
The UPOV convention is the basis for legislation on plant breeders’ rights (PBR) in currently 59 single countries and the European Union. The chapter explains – on the basis of the UPOV convention – who is entitled to plant breeders’ rights and the scope of such rights including its conditions, restrictions, and exemptions. Furthermore, the document details keywords of the legislation to enable applicants for plant breeders’ rights to understand the legal procedure of the granting process. The grant of PBR is independent from regulations on the production or commercialization of a given variety.
Tissue Culture and the In Vitro Environment
1) Somaclonal variation: cause, induction and control
Chapter 32 Somaclonal variation: an important source for cultivar development of floricultural crops. J Chen, RJ Henny, USA (pp 244-253)
Tissue culture has been widely used for propagating disease-free floriculture crops. In vitro culture, however, has often been associated with somaclonal variation. Since the discovery of somaclonal variation in the 1970s, its potential as a source for cultivar development has been debated. Whatever the controversies are, the fact is that somaclonal variation has been an important source for cultivar development of floriculture crops. Floriculture crops are genetically heterozygous and propagated largely through vegetative means. Their value lies in the aesthetic appearance. In vitro culture of this group of crops generates somaclonal variants that could be novel and can be fixed via vegetative propagation. In this chapter, we document somaclonal variation in 58 genera across 33 families of floriculture crops. The occurrence of somaclonal variation may be a result of uncovering somatic mutations that have been accumulated during years of asexual propagation and/or induced mutations during in vitro culture. Changes at the chromosomal level, variation of DNA sequences including activation of transposable elements, and epigenetic effects have been shown to be the underlying mechanisms of somaclonal variation. This chapter also presents methods of somaclonal identification and characterization, and application of somaclonal variation for new cultivar development of floriculture crops.
Chapter 33 Thoughts and tools for reducing variability of in vitro cultures. M Jolicoeur, Canada (pp 254-261)
Plant cells have a unique capacity governing a strong efficiency for survival in a constantly changing environment. This capacity for nutrient accumulation should also govern our way of analysing and managing in vitro cultures. Knowing this, what can we then suggest or identify as potential causes for the high variability level observed in cell culture? And what can we do using which tools in order to reduce culture variability and reach the low levels usually observed for other biotechnological processes such as for bacteria, yeasts, fungi and animal cells? In addition to specific mechanical and hydrodynamic problems (mixing, shear), the capacity of plant cells to accumulate nutrients strongly complicates our capacity to make in vitro culture repeatable. There are increasing evidences that the cells nutritional state determines its potential towards growth and production. Therefore, to our point of view, the understanding and characterization of the role of a cell’s nutritional state on cell behaviour is a key in reducing variability of in vitro culture. Then, this knowledge could be translated into mathematical models capable of describing and predicting cells growth and potential from the estimation of the cells physiological state along a culture (Fig. 1). Efficient tools are thus required for monitoring cell behaviour in vitro, feed the model development and then ultimately define actions to be done on the cells environment for manipulating the cell behaviour towards a desired potential. In this context, this contribution tries to offer some answers to the crucial problem of culture variability which is still limiting the emergence of in vitro plant biotechnology for the production of diverse products of interest such as somatic embryos, plantlets, secondary metabolites and recombinant proteins. More particularly, we will focus on major thoughts explaining plant cell culture variability and on potential solutions that have been identified, developed and validated. Emphasis is placed on suspension cell culture and comments are added for specific cases concerning plant tissues.
Chapter 34 Polysomaty and somaclonal variation in plants. K-I Mishiba, M Mii, Japan (pp 262-270)
The term “Polysomaty” means polyploidization of somatic cells with various ploidy levels in developing plant tissues. In this chapter, we introduce the feature of polysomaty, including molecular mechanisms and biological significance in higher plants. In addition, some examples of polysomaty in several kinds of ornamental plant species, especially orchids, are shown. We also focus the relationship between ploidy variation in plant tissue culture and polysomatic explant tissue source. Some recent observations provide insight into polysomaty present in the original tissue source as being the causal factor for ploidy variation of tissue culture products. This information might contribute somewhat to improve plant tissue culture by being able to control ploidy variation.
Chapter 35 Effect of light qualities on cultured in vitro ornamental bulbous plants. A Bach, B Pawlowska, Poland (pp 271-276)
The effect of light qualities on morphogenesis of ornamental bulbous plants (Tulipa, Hyacinthus, Galanthus, Cyclamen and Freesia) generated in vitro through somatic embryogenesis or organogenesis is described. Varying light treatments (blue, green, yellow, red, far-red and UV irradiation) were studied in long-term cultures. Light qualities affected growth and development of embryogenic tissues depending on the stage of somatic embryogenesis. Darkness, red and yellow light promoted embryogenic callus initiation and proliferation independently on the species of plant. Blue, white and green lights as well as UV irradiation inhibited the proliferation of embryogenic callus culture but stimulated the direct development of globular somatic embryos. Blue light decreased the total number of embryos. Red light improved the maturation of torpedo stage somatic embryos in cultures of tulip, hyacinth and snowdrop. To the contrary, blue light inhibited maturation of somatic embryos. Adventitious shoots and buds growth (number and fresh weight) was stimulated by blue light while the number of bulbs was highest when explants were irradiated with red or yellow light or cultured in darkness. The correlation between the amount of pigments in regenerated tissues and the varying light treatment was noticed. Blue light enhanced the total amount of anthocyanins, while both blue light and UV irradiation promoted the production of chlorophyll a and b. The results obtained indicate that it is possible to control the morphogenesis of ornamental bulbous plants by the quality of light and sequence of spectrum.
Chapter 36 Effects of agar and gel characteristics on micropropagation: Ranunculus asiaticus, a case study. M Beruto, P Curir, Italy (pp 277-284)
In this chapter, we present some technical analyse three different commercial agar brands (Oxoid=OX; Merck=MK and Roth=RT) concerning mineral and phenolic agar impurity content and availability of water, phenolics and minerals for the media gelled with the corresponding agars (0.8% w/v). These analyses have been carried out in our laboratory over a period of ten years and the biological performance, during micropropagation, was evaluated for Ranunculus asiaticus, which is an important ornamental species in Mediterranean countries. On the basis of the relationship between gel properties and growth of Ranunculus shoots, we concluded that the different physiological responses on the three gels are a reflection of different water and nutrient availabilities in different media. Moreover, our analysis carried out to determine identity, concentration and diffusion through the gel of the major agar phenolic impurities revealed their influence on the biological performance of Ranunculus shoots. Our findings could provide additional information on in vitro shoot growth and could be integrated in the complex relationships among the different parameters which can affect the biological performance of in vitro material.
Chapter 37 Prevention of hyperhydricity in plant tissue culture. E Olmos, Spain (pp 285-288)
A major issue in plant tissue culture is hyperhydricity. Recently, the importance of this phenomenon in liquid culture and in bioreactors used for mass propagation has been described. Hyperhydricity has been described as a morphogenic malformation. Hyperhydic tissues show oxidative stress, with the induction of different reactive oxygen species that affect the antioxidant enzyme system. These changes affect the anatomy and physiology of the shoots and their capacity to adapt to these conditions. Hyperhydricity is induced mainly by the modification of the atmosphere of the culture vessels. One of the most important parameters to be control is the relative humidity in the atmosphere of the vessel. Hyperhydricity can be controlled by physical and chemicals methods. The systems used most frequently to prevent hyperhydricity are the use of filter-vent lids or more complex systems such as bottom cooling.
2) Somatic embryogenesis
Chapter 38 Stress drives plant cells to take the road towards embryogenesis. G Potters, Belgium, MAK Jansen, Ireland, Y Guisez, Belgium, T Pasternak, Germany (pp 289-294)
Plant cells have the ability to differentiate and dedifferentiate, as the need and the possibility arises. According to several observations from the last decade, stress conditions may have a clear impact on the onset of embryogenesis. Several protocols have been described for forcing microspores to develop into somatic embryos, using a variety of stressors. Lately, methods for converting isolated leaf cells, explants from flower buds or explants from shoot apices, all by applying some form of stress, have become available. This provides support for a new concept for the meaning of ‘stress’ for a plant cell. Stress is in this respect not a set of negative, damaging conditions, but simply of changing parameters, both environmentally and internally, to which a plant or plant cell has to conform. Transforming a differentiated leaf cell into a dedifferentiated embryogenic cell may be one strategy to adapt to the occurrence of a stress.
Chapter 39 Designing the lighting environment for somatic embryogenesis. T Hoshino, JL Cuello, USA (pp 295-298)
In addition to the biomolecular, physiological and biochemical aspects of somatic embryogenesis, careful design of the lighting environment is necessary to ensure the successful induction and development of somatic embryos for different plant species. The effects of the lighting environment on somatic embryogenesis are certainly dependent on the particular plant species, cultivars and individual genotypes. Based, however, on the seminal studies that investigated the influence of the lighting environment on somatic embryogenesis, certain results exhibited enough consistencies to warrant forming the following two generalizations: (1) Red light generally has promotive effects on the induction of somatic embryos, but generally has neither promotive nor inhibitory effects on the development of somatic embryos; and (2) Blue light generally has inhibitory effects on the induction of somatic embryos, but generally has promotive effects on the development of somatic embryos. Indeed, these generalizations serve as important practical guidelines for the design of the lighting environment for all types of somatic embryogenic systems.
Chapter 40 Somatic embryogenesis, plant regeneration and clonal propagation in different tissue sources of different flowering plants, monocots and dicots. LZ Chen, LM Guan, JA Teixeira da Silva, Japan (pp 299-304)
Tomatoes and cereals are becoming increasingly popular ornamentals in Japan, the former as fruiting pot plants, the latter as dry bouquet supplements. To obtain interspecific hybrids of tomato and its wild species, immature globular-stage embryos were taken out and cultured on suitable medium, on which somatic embryos were formed with globular, heart and torpedo stages. When the initially-obtained embryos were re-cultured on the same medium, secondary somatic embryos were formed and they grew to complete plants. Hereby a clonal propagation system of hybrid embryos was established. Cotyledons of tomato seedlings cultured in a controlled environment chamber were used as materials for protoplast isolation, and plant regeneration was obtained via somatic embryogenesis on TM medium (Shahin 1985). Subsequently, cotyledon protoplasts of tomato treated with iodoacetamide and suspension-culture-derived protoplasts of wild species were fused using polyethylene glycol, and somatic embryos were derived from greenish calli that formed from the fusion mixtures, developed progressively through the globular, heart, and torpedo stages, and finally formed complete plants. In parallel, to establish a simple and efficient culture system of vegetative tissues from monocots for gene transformation, guinea grass and bahia grass were used as starting materials. The leaflet tissues were taken from terminal tillers arising at the end of stolons, cut into 5-mm long pieces, washed, sterilized and then placed on MS medium (Murashige and Skoog 1962). Embryogenic calli were formed and they were observed by scanning electron microscopy, indicating somatic embryo structure with a scutellum and a coleoptile. Multiple shoot and plant regeneration were obtained from somatic embryos. A simple ovary culture system of both was also established via somatic embryogenesis.
Chapter 41 Somatic embryogenesis in floricultural crops: experiences of massive propagation of Lisianthus, Genista and Cyclamen. B Ruffoni, M Savona, Italy (pp 305-313)
For commercial floricultural crops, the promising system to perform massive in vitro propagation is nowadays represented by the possibility to obtain plantlets from somatic embryos and synthetic seeds. The complete structure of the somatic embryos have the possibility to be multiplied in liquid substrate with high multiplication factors that can reduce the manual labour cost and support the authomatization costs. In this paper we report some experiences on somatic embryogenesis and artificial seed production of three important ornamental species: Lisianthus russellianus, Genista monosperma and Cyclamen persicum. The culture protocols established for the three species are presented, and some peculiar aspects of the in vitro culture of each species are explained.
Chapter 42 Micropropagation of Lilium "Gran cru" by somatic embryogenesis. F Fidalgo, A Santos, Portugal (pp 314-316)
An efficient method for regeneration of Lilium Asiatic hybrid “Gran cru” via somatic embryogenesis was developed. For this purpose bulb-scale segments were cultured on a modified Murashige and Skoog medium (Hussey 1982), supplemented with either 2.0 mM 2,4-dichlorophenoxyacetic acid (2,4-D) or 2.0 mM 4-amino-3,5,6-trichloro-picolinic acid (picloram). Induction of embryogenic callus was obtained at 2.0 mM picloram while the auxin 2,4-D failed to induce an embryogenic response. Embryogenic callus predominantly formed from both the basal and middle segments of bulb-scales. Embryo-like structures developed on the embryogenic calli surface. Somatic embryo maturation was achieved when the produced bipolar structures were cultured on similar basic medium devoid of auxin, on which mature embryos developed into normal plantlets. Regenerated plants were transplanted to trays and were successfully acclimatized in glasshouse conditions.
Chapter 43 An effective tissue culture system to regenerate the Persian lilac tree (Melia azedarach). S Sharry, Argentina, JA Teixeira da Silva, Japan (pp 317-324)
An effective tissue culture system to regenerate Melia azedarach (Meliaceae) was established. The optimized protocol resulted in plant formation from cotyledon explants via organogenesis and somatic embryogenesis. Embryogenic callus induction occurred on full strength (salts and vitamins) MS medium containing 3 mg/L 1-naphthaleneacetic acid (NAA) and 1 mg/L 6-benzyladenine (BA) with 3% sucrose with or without 5 mg/L giberrellic acid (GA3). Somatic embryos – induced at 447/g fresh weight of callus – resulted in 100% conversion of somatic embryos to plants, all of which survived in the greenhouse. Organogenic callus was induced on full Murashige and Skoog (MS) medium supplemented with 0.5 mg/L NAA, 1 mg/L BAP, 1 g/L casein hydrolysate (CH) and 5% sucrose. Proliferation and elongation of adventitious shoots – derived from both embryogenic and organogenic callus – was achieved on full MS medium to which 1 mg/L BAP, 200 mg/L CH, 40 mg/L adenine, 80.5 mg/L putrescine and 2% sucrose, or 0.2 mg/l BAP, 0.01 mg/L GA3, 161.1 mg/L putrescine and 3% sucrose were added. The addition of putrescine to the culture media had a positive effect on shoot proliferation. About 160 shoots/ g (fresh weight) callus were produced. Rooted shoots were acclimatized and successfully transferred to soil with 100% survival and whole plants were obtained in ~4 months. Regenerated plants were phenotypically normal. In addition, we developed methods for the in vitro selection for salt tolerance. Organogenic callus culture were screened for salt tolerance using direct selection methods and growth responses were examined. In despite of the presence of salt in culture medium produce lost of the regeneration potential in organogenic callus, plantlets from culture media with 42.7 mm and 85.57 mm concentrations were obtained.
3) Techniques, novelties and tools for improved organogenesis and reduced somaclonal variation
Chapter 44 Advance technology in micropropagation of some important plants. DT Nhut, NT Don, NH Vu, NQ Thien, DTT Thuy, N Duy, Vietnam, JA Teixeira da Silva, Japan (pp 325-335)
The progression of plant biotechnology has been increasingly involved in finding novel methods and culture systems for quality and quantity improvement of plant production. These findings should be applicable for either basic researches or commercial production. They mainly focus on how to optimise regeneration, organogenesis, survival rate, growth and development of valuable medicinal, ornamental and food crops. In this chapter, we discuss several innovative methods in plant regeneration, morphogenesis and propagation. These themes involve (i) positive effect of contaminating microorganisms in plant culture media; (ii) determination of physical, chemical and physiological conditions for in vitro flowering of different floral plants; (iii) novel methods for micropropagation of recalcitrant plants, with the case study of Paphiopedilum delenatii, an endemic and endangered slipper orchid in Vietnam; (iv) investigation and standardization of synseed production in propagation and preservation of some valuable ornamental plants; (v) applications and modifications of some advanced culture systems, namely aeration, temporary immersion and shake culture systems; (vi) control of direct somatic embryogenesis and protocorm-like body formation in Lilium spp.; (vii) microponic culture system for rooting improvement in micropropagation; and (viii) in vitro hydroponics towards a simple and effective culture system for hygrophilous plant material production.
Chapter 45 Test tube bouquets - in vitro flowering. S Sudhakaran, Malaysia, JA Teixeira da Silva, Japan, S Sreeramanan, Malaysia (pp 336-346)
The commercial value of crop plants depends on the quantity and quality of the flowers it produces. Flowering is a complex phenomenon where a number of environmental and endogenous signals play a major role. These signals eventually lead to floral induction. The shoot apical meristem (SAM) integrates the inductive signals, which ultimately gives rise to the flower primordia. The SAM has been the focus of many physiological, biochemical and molecular studies directed toward the understanding of the processes involved in floral transition. Orchids, one of the largest flowering families in the world, are known for its unique flower shapes and attractive colour. Generally they have a long juvenile phase that delays the flowering period. But flowering can be manipulated through photoperiod and plant growth regulators. Recent success of in vitro flowering in orchids, Arabidopsis and in many other plant species have opened up new avenues of research into the flowering mechanism. Such in vitro systems have enabled researchers to unleash the mechanisms involved in flower initiation and development. In this chapter we show how one such plant species, Dendrobium sonia was used as a model for in vitro flowering to explore the possibility of a potential substitute for potted plants.Thin cell layers (TCL) technology has proved to be a powerful tool in the in vitro manipulation of flowers in many species. It offers a solution to many of the issues hindering the efficient improvement of floriculture. TCL technology addresses the issue of plant breeding at the first stage of the problem i.e. regeneration. Since the regeneration of specific organs may be effectively manipulated through the use of TCL, in vitro flowering plant systems may also be potentially created. This review chapter is focused on flowering in general and in vitro flowering in particular to understand the facts and the factors that favor the flowering process. A study was made to describe the efficient nature of TCL technology towards in vitro flower production and briefly reviews the present state of control of in vitro flowering through case studies. Most importantly, an in vitro system for Dendrobium sonia has been standardized and provides the first step in a potential global movement towards a new fashion, “Test Tube Bouquets”.
Chapter 46 Synthetic seed technology in ornamental plants. M Lambardi, C Benelli, Italy, A Ozudogru, Y Ozden-Tokatli, Turkey (pp 347-354)
Synthetic seed technology is today an important tool, available to breeders and scientists, for the in vitro propagation and conservation of ornamental plants. After an introduction on the main procedures for synseed preparation, this chapter provides information on the protocols that have been developed for the encapsulation of various explants (zygotic and somatic embryos, axillary buds, nodal segments, protocorms and bulblets) from ornamental species (trees, shrubs and cut flowers). Original results about the germinability and the average time of germination from 7 ornamental species are also presented. The chapter ends with a review of papers dealing with the application of the synthetic seed technology to the slow growth storage and the cryopreservation of ornamental plant germplasm.
Chapter 47 Micrografting. J Dobránszki, E Jámbor-Benczúr, Hungary (pp 355-359)
Beside the physiology and histology of in vitro micrografting, the methodology is presented, taking into consideration new results mainly from the last ten years. In this chapter a new and efficient (≥90%, including also acclimatization) in vitro micrografting method is described. Main applications of micrografting, such as virus elimination, in vitro culture establishment, rejuvenation, study of compatibility and communication between stock and scion are also discussed. The applications of this technique are outlined and emphasized.
Chapter 48 Androgenesis in trees, ornamental and floricultural plants. A Assani, Canada, B Gupta, India, MV Rajam, India (pp 360-375)
Woody ornamental and floricultural plants play an important role in our lives. Double haploids (DHs) can be useful in breeding strategy of these plants to develop rapidly recombinant homozygote lines, which combine desirable traits. Woody plants are generally allogamy, so that the introduction of DHs in breeding programmes would lead to self-incompatibility and inbred depression. DHs have been established in few angiosperm woody plants like poplar (Popolus nigra), rubber (Hevea brasiliensis Muell Arg.), grape (Vitis vinifera L.) and apple (Malus domestica Borkh.). DHs have also been reported in some ornamental and floricultural plants like lily (Lilium longiflorum), Datura (Datura spp.), Tulipa (Tulipa spp.) and Rosa (Rosa hybrida). In the present chapter, current status of haploid production in various tree, ornamental and floricultural plants are discussed and results from Musa, Malus, Citrus, Coffea, Lilium, Datura, Camellia, Tulipa and Rosa are discussed.
Chapter 49 Parthenogenetic haploid induction via irradiated pollen, dihaploidization and ploidy level determination in vegetable plants. N Sari, H Yetsir, U Bal, Turkey (pp 376-384)
Pure lines, i.e., 100% homozygous lines, are invaluable in plant breeding programs and can be produced gynogenetically. Use of irradiated pollen in pollinations induces parthenogenetic haploids in various vegetable and ornamental plants. Following irradiation of pollen using X or gamma rays, the pollen successfully germinate and tube growth takes place reaching ovules. If fertilization does not take place, however, the egg cell is induced to develop giving rise to haploid embryos which can be rescued at the globular or heart stage, i.e., two to three weeks after pollination. The haploid embryos following culture readily germinate producing haploid plantlets. Chromosome number of the plantlets recovered is doubled via in vitro or in vivo techniques using colchicine. The doubled plantlets, dihaploids, following acclimatization are used successfully in breeding programs. The chromosome number of the plants recovered or doubled can be checked/confirmed via direct or indirect methods such as chromosome counting in the root and shoot tips. Morphological observations of whole plants or organs may be used to differentiate between the haploid and dihaploid plants. In general, haploid plants and organs are smaller. Size of stomata is also another indication of the ploidy level as the haploid plantlets contain smaller stomata. Flow cytometry, an indirect method for ploidy level determination, also gives accurate results. The parthenogenetic induction of haploidy, in some vegetable crops such as melon, watermelon, squash and cucumber – several of which are also produced for ornamental fruits and decoration – is now an established technique. However the technique is open to further improvement to increase the frequency of haploids induced. An important drawback of the technique is that an irradiation source is a must therefore hinders its much wider use. An alternative method to obtain the same irradiation effect would facilitate its use both in research and in commercial breeding.
Chapter 50 Plant protoplast biotechnology in floriculture. MR Davey, P Anthony, JB Power, KC Lowe, UK (pp 385-396)
The floriculture industry is driven by consumer demand for novel flower architecture and colour. Such traits have been generated by on-going selection and domestication of wild species, combined with sexual hybridization. Laboratory-based technologies are available to underpin conventional breeding. Such technologies include micropropagation to multiply elite ornamentals, somatic hybridization to overcome naturally-occurring sexual incompatibility between species and genera, and genetic transformation to introduce specific genes into plants. Cell culture per se may expose naturally-occurring genetic variation. Isolated protoplasts, initially lacking cell walls (‘naked cells’), are totipotent when given the correct stimuli in culture. Robust protoplast-to-plant systems, now available for many ornamental plants, are fundamental to gene mobilization by somatic hybridization and transformation. Totipotent protoplasts are most relevant to the genetic improvement of ornamentals through the generation of somatic hybrid and cybrid plants, since the genetic novelty created by protoplast fusion cannot be matched by conventional breeding.
Chapter 51 Enhancing plants with endophytes: potential for ornamentals? T Dubois, CGIAR, CS Gold, IITA-ESARC, P Paparu, S Athman, S Kapindu, Uganda (pp 397-409)
Plants are naturally associated with mutualistic microorganisms that include endophytes. Endophytes are a diverse group, and an overview of the major fungal and bacterial endophytic taxa is provided. The potential for biological control using endophytes is vast. Using endophytes as microbial control agents might circumvent some of the problems associated with other biological control agents, such as lack of targeted application or high inoculation rates. Benefits of endophytes are manifold and not only include antagonism to pests and diseases, but also other benefits such as plant growth promotion. Endophytes employ several modes of action against pests and diseases: parasitism, competition, production of secondary metabolites, indirect effects through plant growth and induced plant resistance. Through induced plant resistance, endophytes trigger plant defence mechanisms prior to infection, resulting in reduced pest or pathogen damage. The role of induced resistance is only now beginning to be understood and offers new possibilities into targeting pests and diseases. Since endophytes are sometimes closely related to plant pathogens, the risks and fitness costs resulting from their potential use is discussed. Surprisingly, research into endophytes for the ornamental industry has been little explored. Lessons learnt from our work on banana endophytes are discussed, together with future applications such genetic modifications and application of endophyte combinations.
Chapter 52 Advances in orchid cryopreservation. T Hirano, K Ishikawa, M Mii, Japan (pp 410-414)
The vast majority of orchids are currently endangered due to extensive disturbance of their natural habitat and indiscriminate harvesting of the naturally growing plants. Therefore, it is urgently needed to establish reliable methods for conserving these orchids as valuable germplasms. Cryopreservation is found to be one of the most effective methods for long-term storage of genetic resources and significant progress has been made in the field of cryopreservation techniques in recent years. Three cryopreservation methods, namely desiccation (air-drying), vitrification, and encapsulation-dehydration methods, have already been applied for orchids, and various types of orchid genetic resources such as pollen, immature and mature seeds, protocorms, protocorm-like bodies, apical meristems and suspension cells have been successfully cryopreserved. Here these successful cryopreservation studies on orchids are summarized. Although these results are mostly encouraging with respect to the prospect for the long-term conservation of orchids, further studies are still required before a generalized protocol for orchid conservation is established. Therefore, problems encountered using these methods for orchid materials are also discussed.
Chapter 53 Cryopreservation of carnation (Dianthus caryophyllus L.). A Halmagyi, Romania, M Lambardi, Italy (pp 415-423)
After a concise outline of the recent advances in tissue culture, genetic engineering and in vitro conservation of the carnation (Dianthus caryophyllus L.), this chapter examines the potential of the cryogenic technology for the long-term preservation of valuable carnation germplasm. A comparison between various methods (“PVS2-droplet freezing”, “DMSO-droplet freezing”, and “encapsulation-dehydration”) which allow the direct immersion of shoot tips in LN is reported, carrying out the study with 6 carnation cultivars (‘Anthares’‚ ‘Coralie’, ‘Kinero’, ‘Pallas’, ‘Pink Candy’ and ‘Wanessa’). Maximum shoot formation after cryopreservation (from 53% for cv Coralie to 65% for cv Wanessa) was achieved after a PVS2-droplet freezing procedure was optimized. Lower percentages of shoot formation were obtained when the DMSO-droplet freezing and the encapsulation-dehydration methods were developed. After the plants from cryopreservation were potted and transferred to the greenhouse, a comparison with control plants did not evidence any sign of morphological alteration or abnormalities in growth.
Chapter 54 Cold storage of in vitro shoot cultures and chemical evaluation of regenerated plants. N Hiraoka, Japan (pp 424-426)
This chapter deals with the cold storage of two types of cultures: callus and mainly shoot. The emphasis lies on the effect of cold storage on secondary metabolism in both types of cultures. Callus tissues survived cold storage at 4ºC for 1-8 months depending on the plant species. Production of secondary metabolites such as nicotine and betalain pigments was strongly inhibited by cold storage. However, anthocyanins and naphthoquinone derivatives were less affected following reculture of callus. In vitro shoot cultures of temperate plant species were able to tolerate cold storage at 0-5ºC for 1-2 years whilst those of tropical species at 10-15ºC for about 1 year without transfer. The plants regenerated from cold-preserved shoots had a normal biosynthetic capability, which indicated that cold storage of in vitro shoots is a dependable method for short- to medium-term germplasm conservation including secondary metabolism.
Chapter 55 Effective acclimatization of in vitro cultured plants: Methods, physiology and genetics. BN Hazarika, India, JA Teixeira da Silva, Japan, A Talukdar, India (pp 427-438)
Culture in vitro has become an important technique in plant production. Substantial numbers of in vitro cultured plants do not survive transfer from in vitro conditions to the greenhouse or field environments. In vitro grown plants are very tender and delicate owing to high humidity in the culture vessel, controlled temperatures, low light intensities and hetero or mixotrophic mode of propagation under which they are normally grown. They lack protective mechanisms like waxy cuticles, stomatal regulation and leaf hairs, they show reduced differentiation of palisade cells and exhibit large inter-cellular spaces which make them vulnerable to desiccation once exposed to ambient temperatures. Understanding the physiological and morphological characteristics of in vitro cultured plants and the changes they undergo during the hardening process should facilitate the development of efficient transplantation protocols. Most species grown in vitro require an acclimatization process in order to insure that sufficient number of plants survive and grow vigorously when transfer to soil. Successful acclimatization procedure provides optimal conditions for minimal damage of plants in the micropropagation process and thus enhances the plant growth and establishment. The chapter discusses the anatomical, morphological and physiological factors that accounts for the fragility of cultured plants and also highlights the techniques that are most satisfactory for acclimatization of in vitro cultured plants. Understanding the mechanism of genetic control of acclimatization may pave the way of improving the regeneration and final establishment efficiency of in vitro regenerated plants. Genotypic variations with regards to response to regeneration, organogenesis and final ex vitro establishment have been discussed. Molecular studies to map and clone the gene(s) affecting the process of acclimatization and the scope to develop corresponding transgenics are also reviewed.
Chapter 56 Utilization of nylon film in regeneration and micropropagation of some important plants. DT Nhut, NH Vu, NT Don, Vietnam (pp 439-443)
In this chapter, nylon film culture systems are presented with experimental application in several objective species/varieties; their positive results and obstacles in system design are also discussed. These works are to be developed into large-scale production towards a commercial plant production with high quality and quantity in regard of enhancing ventilation and making new substrata for plant culture industry.
Chapter 57 Molecular markers in plant tissue culture. Y Aka Kacar, Turkey, PF Byrne, USA, JA Teixeira da Silva, Japan (pp 444-449)
In vitro regeneration and micropropagation form the primary core of many, if not most, horticultural, ornamental and agricultural crop studies. The establishment of in vitro cultures – often from the ex vitro environement – and subsequent (re-)acclimatization often involves changes at the morphological and cytogenetic levels, but often undetectable to the naked eye. In order to limit the inclusion of such variation (somaclonal or otherwise) in standardized plantations commonly needed for breeding programmes or homogenous markets, and to detect it, molecular markers have proved a valuable tool to monitor this variation. This chapter explores the wealth of molecular markers commonly employed in tissue culture, their strengths and weaknesses, and applications.
Chapter 58 In vitro cell culture systems of Zinnia elegans. MA Pedreño, C Gabaldón, RV Gómez Ros, A Ros Barceló, Spain (pp 450-457)
Zinnia is a rather coarse, easily cultivated annual herb, popular as a cut flower for its warm colors and for its bold, upright appearance. Most zinnias on the market are derived from Z. elegans. One of the reasons for zinnia’s popularity is the diversity of its forms since, like dahlias and chrysanthemums, they may be single, semi-double, double, cactus, dahlia, and scabious. Zinnias also constitute one of the most useful models for plant biologists, especially for those working in xylem differentiation, a unique process in developmental plant biology, which simultaneously involves secondary cell wall synthesis (which includes lignin biosynthesis) and programmed cell death. In this contribution, and after reviewing zinnia’s history, we turn our attention to two zinnia in vitro cell culture systems considered useful tools for studying the cell wall lignification process occurring during xylem ontogeny.
Chapter 59 Micropropagation and in vitro flowering in medicinal plants - a method for microbreeding. J Batra, A Dutta, M Jaggi, S Kumar, J Sen, India (pp 458-464)
The rapid expansion of phytopharmaceutical industries and the ever increasing demand for natural resources of important life-saving plant-based drugs have placed great pressure on the natural existence of a number of economically important plants, otherwise known as medicinal plants. Commercial farming of medicinal plants is one way to ease this pressure. However, in cases where some plants show low germination rate or need special ecological growth requirements, in vitro propagation methods have been proved to be a useful alternative for conservation of elite germplasm. In this chapter, we discuss the possibilities and methods for successful application of in vitro techniques for mass multiplication of a wide variety of medicinal plants with a special reference to Catharanthus roseus. Potential of in vitro flowering of regenerated medicinal plants has also been discussed here, which has hitherto been explored to a limited extent.
4) Scaling-up and mass production systems
Chapter 60 Latest applications of Thin Cell Layer (TCL) culture systems in plant regeneration and morphogenesis. DT Nhut, NT Hai, NT Don, Vietnam, JA Teixeira da Silva, Japan, K Tran Thanh Van, France (pp 465-471)
Scientists within the field of plant biotechnology are in a constant search for techniques that can, in the simplest manner possible, answer the genetic and biochemical questions that underlie development processes. The thin cell layer (TCL) culture system not only takes an in-depth look at a technique that has had so much success in attempting, through various practical models and systems, to answer the issues, but also represents a celebration of almost 30 years of research that has covered a massive scope of plant species and areas of study. This chapter brings to the reader exciting new advances brought to you by the founder and leaders of TCL technology, showing the continued importance of TCL regeneration systems for mass-propagation of plants, with special reference to ornamentals.
Chapter 61 Application of bioreactor systems for mass propagation of horticultural plants. KY Paek, South Korea, D Chakrabarty, India (pp 472-477)
Conventional micropropagation technique is a typically labor-intensive means of producing elite clones. High production costs generally limit the commercial use of micropropagation. Bioreactor technology offers various advantages due to possibilities of automation, saving labor and reducing production costs by providing optimum growth conditions to achieve both maximum yield and high quality of propagules, or to keep the production costs as low as possible by integrating automated facilities and simple low cost devices. The use of bioreactor technology is starting to be commercialized and the results suggest the practical applicability of this technique in plant propagation. Here we attempted to focus on the development of cost-effective methods for commercial micropropagation of several important horticultural plants using a bioreactor system and also to identify the problems related to large-scale plant micropropagation.
Chapter 62 Potentialities of hairy root cultures for in vitro essential oil production. AC Figueiredo, JG Barroso, LG Pedro, Portugal, JJC Scheffer, The Netherlands (pp 478-486)
Roots are much more than an organ that provides transport of water and solutes from the soil to the above ground parts of a plant. The recognition that roots possess a unique physiology and that they can contribute with biologically active chemicals to the environment expanded the field of root research. In this context, hairy roots became a unique experimental system, due to their high biomass growth allied to their biosynthetic capacity. In addition, hairy roots constitute a good system for the study of metabolic pathways, of root growth and primary and secondary metabolism, of their behaviour under stress-inducing environments, of the interrelationships of roots with biotic and abiotic factors, as well as the production of regenerants. The production of essential oils by hairy roots demonstrates a biosynthetic ability that can attain higher yields than in undifferentiated cultures and is sometimes equal to or higher than the parent plant. This capacity is strictly correlated with the differentiated state of the cultures, the level of production being severely impaired or lost when the hairy root phenotype is lost. Other factors, e.g. the type and/or age of the inoculums, the gap between subcultures, the combinations of nutritional and environmental stressing factors, including different medium composition, photoperiod conditions, and cultivation in a two-phase system and biotransformation, can also affect biomass growth and product performance. The possibility of growing and maintaining in vitro hairy root cultures of different species widens the indispensable basic knowledge needed to manipulate, in a controlled way, their molecular, biochemical and ecological potential.
Chapter 63 Matrix-supported liquid culture systems for efficient micropropagation of floricultural plants. S Dutta Gupta, VSS Prasad, India (pp 487-495)
Conventionally the culture medium is gelled to simulate a native soil-like environment for in vitro plant growth and differentiation. However, the use of gelling agent poses many problems such as, sensitivity of tissue to gelling agent type and concentration; alteration and/or inactivation of media components during heat sterilization; mechanical impedance of movement and availability of dissolved oxygen, water and ions; labor and time intensive cleaning of tissues and vessels before transplantation, transferring or sub-culturing. The use of liquid media circumvents these problems; allows even faster and more prolific tissue growth. Liquid systems are also amenable to automated large-scale micropropagation. However, direct and prolonged contact with liquid medium and lesser oxygen availability due to partial or complete submergence makes the tissue hyperhydric. Hyperhydric tissue exhibits recalcitrance and the affected plantlets strive to acclimatize upon ex vitro transfer. The use of inert support substrates abbreviates tissue hyperhydration, yet retaining the various advantages of liquid media. The present chapter is focused on various studies pertaining to the use of support systems like Coconut coir, Cotton fiber, Filter paper, Glass wool, Luffa sponge, Nylon cloth, Polystyrene foam, Polyester screen raft, Polypropylene membrane raft for micropropagation of floricultural crops. The chapter also highlights Poisson regression based analytical approach unlike customary ANOVA for critical assessment of in vitro shoot regeneration in liquid systems.
Chapter 64 Madagascar periwinkle, an attractive model for studying the control of the biosynthesis of terpenoid derivative compounds. N Giglioli-Guivarc'h, V Courdavault, A Oudin, J Crèche, B St-Pierre, France (pp 496-506)
Isoprenoid biosynthesis occurs in plants via the plastidic and cytosolic pathways respectively named the methyl-erythritol phosphate (MEP) and mevalonate (MEV) pathways. For monoterpenoid indole alkaloids, the MEP pathway exclusively provides the terpenoid moiety. In this paper, we reviewed findings and observations that made C. roseus a model plant for monoterpenoid indole alkaloids biosynthesis and regulation studies. If the whole plant has been essentially used to establish the scheme of the spatial organization of the biosynthetic pathway between four different cell types, the cell suspension cultures have proven to be an excellent system for studying the regulation of the plastidial isoprenoid biosynthetic pathway. Due to the ability of cell suspensions both to take up chemical components and, with an apparent ease, to be genetically manipulated and transformed, a set of regulatory elements of monoterpenoid indole alkaloids biosynthesis starts to emerge. Technical approaches and results are discussed in the context of the recent literature.
Chapter 65 High-value metabolites from Hypericum perforatum: a comparison between the plant and in vitro systems. G Pasqua, P Avato, N Mulinacci, Italy (pp 507-513)
Hypericum perforatum L. (St. John’s wort) is a medicinal plant used for the treatment of neurological disorders and mild to moderate depression. Hypericum perforatum is also used as a garden ornamental plant in perennial hedges or in rock gardens. Recent studies have been conducted to investigate the productivity on a large-scale of in vitro growth systems such as undifferentiated calli, cell cultures, somatic embryos and regenerated shoots. Accumulation of bioactive molecules (hypericins, hyperforin, xanthones, flavonoids, procyanidins and anthocyanins) has been compared with that in wild and greenhouse-grown plants. In vitro studies demonstrated that shoot cultures accumulate greater amounts of different metabolites compared to calli and cell suspension cultures. Moreover shoot cultures demonstrated to be a good source for both hypericins and hyperforin production.
5) Applied case-studies
Chapter 66 In vitro culture of Rosa species. M Khosh-Khui, Iran, JA Teixeira da Silva, Japan (pp 514-526)
The genus Rosa comprises hundreds of species and thousands of cultivars. Roses are, undoubtedly, one of the most economically important and favorite ornamental plants. Millions of rose bushes are planted in gardens or pots and billions of rose cut flowers are sold annually over the world. A number of species are also used for highly-prized essential oils (attar). Traditionally, rose species or cultivars are propagated by seeds, cuttings, budding or grafting. Propagation by seeds may not breed true-to-type and vegetative propagation is also very slow, time-consuming and may be a limitation in stock plants. Alternate systems of rose propagation are needed to eliminate or minimize these problems. In vitro culture of roses are one of the most exciting procedures of producing new cultivars, eliminating the use of rootstocks for different soil conditions, cultivars adaptable to different environmental conditions, providing rapid multiplication of superior cultivars and rootstocks, producing disease-free plants and speeding up breeding programs. In this review, with the emphasis on advances in the field of rose in vitro culture, we first briefly review early research, and then in separate sections, the studies related to media preparation (basic salts, sucrose, agar, pH and growth regulators) for callus culture, shoot regeneration and multiplication, rooting and cell suspension culture and embryogenesis. The stages of rose in vitro culture, including establishment, multiplication, in vitro rooting, acclimatization and genetic variation are also reviewed. Subsequently, investigations on methods of rose in vitro culture by callus, pollen, anther, cell suspension and protoplast culture are described. Finally, technological improvements for micropropagation, embryogenesis, biotechnology and plant breeding are discussed. Views and conclusive prospects of these techniques are also expressed.
Chapter 67 Pelargonium embryogenesis. M Borja, Spain, M Alonso, Ireland (pp 527-532)
Due to fact that geraniums (Pelargonium spp.) are of interest as ornamentals or as essential oils producers, in vitro tissue culture has been widely used for the multiplication and production of healthy plants. The majority of studies have been focused on commercially interesting species such as Pelargonium x hortorum, P. peltatum, P. x domesticum and P. graveolens. Even if the production of phenolic compounds is a big handicap to the in vitro establishment of Pelargonium explants in solid media, various authors have described the regeneration of geranium plants (Pelargonium spp.) using explants such as meristems, anthers, leaves, petioles, stem sections, roots, hypocotyls or cotyledons. In most cases, the regeneration of Pelargonium plants needed to pass through a callus state. Somatic embryogenesis can be used for large-scale vegetative propagation, but so far the production of Pelargonium somatic embryos has only been described for a small number of genotypes from seed-derived cultivars but not for vegetatively propagated cultivars. In of our investigations only root explants from vegetatively propagated geraniums were capable of embryogenesis. Pelargonium embryogenesis can be used not only for clonal multiplication, but for the breeding of new cultivars.
Chapter 68 Micropropagation of selected cultivars of Lilium and Gladiolus spp. EV Mokshin, AS Lukatkin, Russia, Jaime A. Teixeira da Silva, Japan (pp 533-539)
The patterns of clonal micropropagation in vitro of selected cultivars of longiflorum-Asiatic hybrid lily (Lilium L.) and gladiolus (Gladiolus L.) have been investigated. The optimal culture conditions maximizing regeneration capacity of plants at different stages of morphogenesis were determined. The effectiveness of these results, which are novel, are compared to others available in the literature for other cultivars.
Chapter 69 Micropropagation of tropical bamboos. SMSD Ramanayake, Sri Lanka (pp 540-550)
The global focus on bamboo as a unique natural resource for the future has created an awareness of the importance of its cultivation at a plantation-scale. The existence of rare seeding and physiologically sterile species makes tissue culture an important technique for their propagule production and improvement. Axillary shoot proliferation and somatic embryogenesis have been used for propagule production in bamboo species. Culture initiation especially from adult field culms, difficulty of rooting of axillary shoots and the inconsistency in somatic embryogenesis are some of the difficulties encountered. Seeds are not dependable for culture initiation but could always be used whenever available. The use of plant parts from field culms of known performance is more dependable. The determinate branching pattern of bamboo, bud dormancy and presence of microbial contaminants makes culture initiation from field culms difficult. However, when nodes with axillary buds are cultured at periods of physiological activity, they can readily sprout in vitro. Microbial contaminants are also eliminated relatively more easily than at other times. Reports show that rapid and continuously proliferating axillary shoots were developed from in-vitro sprouted shoots in the presence of a relatively high level of 6-benzlaminopurine (BA) in many species but the difficulty of rooting had made this technique commercially applicable for only a few species. Somatic embryogenesis was also possible but its application on a commercial-scale appears to be limited due to inconsistency in regeneration and germination of embryos. This chapter attempts to discuss the problems related to these techniques and identifies a protocol applicable for producing propagules by axillary shoot proliferation leading to a high degree of rooting and survival of plantlets.
Chapter 70 In vitro morphogenesis of dwarf irises. S Jevremović, A Subotić, L Radojević, Serbia and Montenegro (pp 551-557)
In vitro plant regeneration of Iris pumila and I. reichenbachii from the culture of mature embryos and leaf bases of in vitro grown shoots as well as cell suspensions has been studied. During the regeneration process, two different regeneration pathways were observed: somatic embryogenesis and/or organogenesis. Embryogenic calli were developed on MS medium supplemented with 2,4-D alone or 2,4-D and kinetin in combination (1.0 mg l-1 each). Cell suspension cultures were established and maintained in MS liquid medium at the same concentration of 2,4-D and KIN as used for the induction and proliferation of embryogenic calli. These were initially composed of single cells, bi-, three and multicellular proembryos and cell aggregates. In prolonged cell suspension cultures (6-8 weeks) three types of embryogenic calli were observed: yellow, compact; yellow-green and white, friable. Friable (white, yellow green) suspension-derived calli had the greatest morphogenetic potential. Germination of normally developed somatic embryos (70%) was achieved on MS solid medium without hormones. Organogenic calli were cultured on MS medium supplemented with BAP and GA3 (1.0, 0.1 mg l-1, respectively) for ten years. Shoots can be easily rooted after one month on hormone free medium. Potted plants of investigated dwarf irises grew normally and flowered.
Chapter 71 Heliconia bihai var. Lobster Claw I: cut-flower field production from micropropagated- versus rhizome-derived plants. PHV Rodrigues, GMB Ambrosano, AMLP Lima, BMJ Mendes, APM Rodriguez, Brazil (pp 558-560)
Micropropagation has been used in several ornamental species such as orchids, bromeliads, anthurium, African violet and heliconias for the large-scale commercial propagation of high quality plants. The in vitro establishment of a new species should be followed by field evaluation of its behavior to guarantee the maintenance of the agronomic characteristics. Heliconia bihai var. Lobster Claw I plants obtained from rhizomes and from in vitro multiplication were planted in the field. Two hundred plants of each were planted in alternate rows, 20 plants per row, with 10 replications. The experiment was evaluated by the number of suckers, time for flowering initiation and cut flower productivity. Flowering was initially observed after 7 months in the field in rhizome-derived plants. The number of suckers however was higher in micropropagation-derived plants, resulting in a higher productivity. In addition to a high cut flower production, the market price per plant derived from micropropagation is approximately one third of that for rhizome-derived plants, which makes establishment of a field crop of this species from in vitro propagated plants even more viable.
Chapter 72 In vitro propagation of Hyacinthus orientalis cv. Jan Boss from bulb twin scale explants. A Santos, F Fidalgo, I Santos, Portugal (pp 561-563)
Hyacinthus orientalis cv. Jan Boss has great importance in cut-flower commerce. For in vitro production of bulbs of this cultivar, twin-scales were cultured on a modified Murashige and Skoog medium containing 3% sucrose and supplemented with 1 mg/l IBA + 0.1 mg/l BA or 1 mg/l IBA + 1 mg/l BA. Both media were appropriate for bulb induction, but the medium with equal amounts of both IBA and BA was the most suitable, as on this medium the number of responsive explants and the number of bulbs per explant was higher. Further growth of the bulbs and root production was achieved on a similar basic medium without growth regulators and with increased sucrose content (6%). Rooted bulbs with a mean diameter of 8 mm were adequately prepared for ex vitro culture and grown in a glasshouse with high success of transplantation rate.
Chapter 73 Plant tissue culture and secondary metabolite production of Centaurium erythraea Rafn., a medicinal plant. A Subotiċ, T Jankoviċ, S Jevremoviċ, D Grubišiċ, Serbia and Montenegro (pp 564-570)
Plant species that belong to the genus Centaurium are wide-spread in International traditional medicine. Centaurium erythraea Rafn. (European Centaury) is a biennial plant, with attractive pink flowers, and for potential as a medicinal-ornamental used in the treatment of gastrointestinal tract diseases, in the treatment of fever and anaemia, and for increasing appetite. The effects of some plant growth regulators, nutrient medium components and different light treatments on modification of the morphogenetic response of this plant were examined. The seeds collected in their natural habitat were surface sterilised, and germinated and establish in vitro. Seedlings were cultivated on hormone-free? MS basal medium. Root segments (average 15 mm long) isolated from seedlings were used as an initial material for establishing non-transformed root cultures. After ten days of growth on the basal medium, somatic embryos were observed to form on the initial explants. Towards the end of the subculture period, a large number of adventitious buds also formed at the basal part of explants, beside somatic embryos. Both morphogenetic processes are asynchronous. Histological studies revealed that somatic embryos were formed directly from epidermal cells and adventitious buds from meristematic cells derived from root cortex tissues. C. erythraea seedlings were inoculated with Agrobacterium rhizogenes strain A4M70GUS so as to set up a transformed root culture. In vitro plant material, was analysed by relevant methods and results were compared to plants collected in nature. The results showed that in vitro culture of C. erythraea produced greater amount of secoiridoid glucosides and xanthones.