Volume 1 Number 1 2007

CONTENTS AND ABSTRACTS

Stephen J. Trueman, Geoff S. Pegg, Judith King (Australia) Domestication for Conservation of an Endangered Species: The Case of the Wollemi Pine (pp 1-10)

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Invited Review: A small population of tall slender conifers was discovered in 1994 in a deep rainforest canyon of the Wollemi National Park, New South Wales, Australia. The living trees closely resembled fossils that were more than 65 million years old, and this ‘living fossil’ was recognised as a third extant genus in the Araucariaceae (Araucaria, Agathis and now Wollemia). The species was named the Wollemi pine (W. nobilis). Extensive searches uncovered very few populations, with the total number of adult trees being less than 100. Ex situ collections were quickly established in Sydney as part of the Wollemi Pine Recovery Plan. The majority of the ex situ population was later transferred to our custom-built facility in Queensland for commercial multiplication. Domestication has relied very heavily on the species’ amenability to vegetative propagation because seed collection from the natural populations is dangerous, expensive, and undesirable for conservation reasons. Early propagation success was poor, with only about 25% of cuttings producing roots. However, small increases in propagation success have a very large impact on a domestication program because plant production can be modelled on an exponential curve where each rooted cutting develops into a mother plant that, in turn, provides more rooted cuttings. An extensive research program elevated rooting percentages to greater than 80% and also provided in vitro methods for plant multiplication. These successes have enabled international release of the Wollemi pine as a new and attractive species for ornamental horticulture.

Krystyna Klimaszewska (Canada), Jean-François Trontin (France), Michael R. Becwar (USA), Christine Devillard (New Zealand), Yill-Sung Park (Canada), Marie-Anne Lelu-Walter (France) Recent progress in somatic embryogenesis of four Pinus spp. (pp 11-25)

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Invited Review: Advances in conifer biotechnology offer new opportunities in the field of vegetative propagation and genetic engineering. Development of clonal propagation methods, especially somatic embryogenesis (SE), has numerous potential applications. Owing to its efficiency in plant regeneration, coupled with the ease of long-term storage in liquid nitrogen, SE became an indispensable tool for accelerating the development of tree varieties and deployment. Early SE protocols were developed for Picea species, however, when applied to Pinus species, especially at the somatic embryo maturation stage, they were unsuccessful. It became apparent that pines required more research and development to bring the SE biotechnology to its potential. This review emphasizes the most recent progress made in SE and cryopreservation in the genus Pinus, focusing on major plantation and forest species in Europe (Pinus pinaster), New Zealand, Australia, and South America (P. radiata), as well as North America (P. taeda and P. strobus). Much consideration is also given to applying SE in pine improvement and deployment strategies in multivarietal forestry.

Panos V. Petrakis, Costas Ionnidis, Anna-Maria Zygomala (Greece) Biotechnology of Pinus brutia and Pinus halepensis as Important Landscape Plants of the East Mediterranean (pp 26-38)

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Invited Review: Aleppo and Calabrian pines (Pinus halepensis and P. brutia) are members of the Mediterranean flora. They are thought to replace the evergreen sclerophylous species in cold periods and they are used as important indicators of adverse abiotic conditions. Although ancient people in the area used the pines in many different ways, they are presently used in reforestation projects in burnt areas, city parks and “Mediterranean gardens” as ornamental trees. The methods of biotechnology are now appearing to be applied on these trees. Genetic engineering, although recognised as important in selecting genotypes resistant to pests, faces strong reaction as severely impacting non-target organisms. The suggested precautions from experts applied to all genetically modified organisms in order to prevent the spread of genes from transgenic pines to other pines in natural populations do not seem at present to affect the opinion of many nature-passionate defenders against genetically engineered methods. The selection of specific genotypes having unattractive or even repellent terpenoid profiles is similarly ecologically problematic on the basis that the normal pine arthropod fauna would not recognise the altered pine profile. This is an especially unwanted result since it includes predators and parasitoids that keep in nature the population densities of pests at reasonable levels. Micropropagation techniques have already been developed for these two pine species with successful results. Semiochemical technology incorporating recent controlled release formulations involving supra-molecular models have been applied in many cases in pine formation with promising results. Many European and North American commercial firms have already developed and released products that are effective against insect pests of these pines species.

Bozena Vooková, Andrej Kormuták (Slovak Republic) Abies Biotechnology - Research and Development of Tissue Culture Techniques for Vegetative Propagation (pp 39-46)

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Invited Review: The genus Abies represents a large group of coniferous species growing in different parts of the world. This review is a compilation of the available literature referring to Abies in vitro cell, tissue and organ culture, micropropagation, somatic embryogenesis and transformation. Our data presented within this context cover such aspects of Abies biotechnology as initiation of callus, plantlet regeneration via axillary and adventitious buds development and subsequent rooting. Somatic embryogenesis has been regarded as a model for large-scale propagation of tree species through out the world. Also in Abies, the best results have been achieved using technics of somatic embryogenesis. The factors affecting induction of embryogenic tissue, somatic embryo maturation and germination are discussed. Emphasis has been given on comparisson of soluble and insoluble protein profiles and enzyme activity during zygotic and somatic embryogenesis. Recent experiments concern cryopreservation of embryogenic cultures, genetic transformation and regeneration of transgenic plants.

Jaime A. Teixeira da Silva, Zinia Rashid (Japan), Duong Tan Nhut (Vietnam), Dharini Sivakumar (South Africa), Abed Gera (Israel), Manoel Teixeira Souza Jr. (The Netherlands), Paula F. Tennant (Jamaica) Papaya (Carica papaya L.) Biology and Biotechnology (pp 47-73)

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Review: Papaya (Carica papaya L.) is a popular and economically important fruit tree of tropical and subtropical countries. The fruit is consumed world-wide as fresh fruit and as a vegetable or used as processed products. This review focuses primarily on two aspects. Firstly, on advances in in vitro methods of propagation, including tissue culture and micropropagation, and secondly on how these advances have facilitated improvements in papaya genetic transformation. An account of the dietary and nutritional composition of papaya, how these vary with culture methods, and secondary metabolites, both beneficial and harmful, and those having medicinal applications, are discussed. An overview of papaya post-harvest is provided, while ‘synseed’ technology and cryopreservation are also covered. This is the first comprehensive review on papaya that attempts to integrate so many aspects of this economically and culturally important fruit tree that should prove valuable for professionals involved in both research and commerce.

Kamlesh Kanwar, Anju Bhardwaj, Raj Deepika, D.R. Sharma (India) Robinia pseudoacacia Linn. (pp 74-80)

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Invited Mini-Review: Robinia pseudoacacia L. is a nitrogen-fixing, leguminous, fast-growing and multipurpose agroforestry tree adapted to drought-affected and degraded sites. Recent interest in woody biomass as a source of fuel has fostered additional investigations into the culture of R. pseudoacacia. In trials of potential biomass species, it demonstrated superior growth rates and energy yields. However, because of its rapid growth, early flowering, adaptability to drought and degraded sites it is widely planted through out the world’s temperate zone for multiple purposes. These advantages suggest the possibility of selecting variants for tree improvement. Improvement by conventional tree improvement programmes is cumbersome and time-consuming, while in vitro propagation techniques offer an alternative approach. This species has been regenerated in vitro by micropropagation, protoplast and cell suspension culture. These biotechnological tools can be used for mass propagation, induction of genetic variability, production of disease-free and stress-tolerant plants from isolated cells, protoplasts and tissues and introduction of transgenic trees following molecular characterization.

Simon A. Mng’omba (South Africa/Malawi), Elsa S. du Toit (South Africa), Festus K. Akinnifesi (Malawi) Germination Characteristics of Tree Seeds: Spotlight on Southern African Tree Species (pp 81-88)

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Invited Mini-Review: Many tree species of economic potential are propagated by seeds, but seed germination information is limited due to inadequate research. This frustrates genetic conservation, ecosystem restoration, domestication and biodiversity efforts. Deforestation, floods, drought and other disasters are endemic to many countries of Africa and these have a negative impact on the availability of many tree species which have a significant contribution as food and income sources. This review takes stock of seed germination and storage behavior of some important southern African tree species. Recalcitrant and orthodox seeds are the two extreme seed germination behaviors distinctly discussed, but information on seed germination and storage behavior of many southern African tree species is limited. Furthermore, knowledge on seed dormancy of recalcitrant or orthodox tree seeds is limited. Orthodox seeds tolerate relatively long storage periods, and hence have inherent primary seed dormancy. Seed dormancy for many recalcitrant tree seeds is not well explained, but such seeds are sensitive to desiccation injury and have a short storage period. Seed germination and storage behavior of many southern African tree species are not fully established with respect to secondary metabolites, fruit pulp composition, growth hormones and physical impediments. In this review, seed germination and storage behavior and different germination barriers will be the main focus.

Marcos Daquinta, Yarianne Lezcano, Mariela Cid, Danilo Pina, Romelio Rodríguez (Cuba), Jaime A. Teixeira da Silva (Japan) In Vitro Morphogenesis of Toona ciliata and Swietenia Hybrid (pp 89-91)

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Short Communication: The Meliaceae are of great importance in construction and furniture-making. Toona ciliata is a member of this family originally from the Himalayan Region; in Cuba it is known as Himalayan Cedar. The Swietenia natural hybrid results from a cross between Swietenia mahogany x Swietenia macrophylla. Natural regeneration occurs in these species by seed and grafting but such propagation is limited, while there exist no reports on their in vitro culture. The objective of this paper was to promote callus formation and plant regeneration in theses two species. Two to three year-old mature T. ciliata and 40 year-old Swietenia hybrid trees were used. The rachis of Toona and the inflorescences of Swietenia were taken from young branches from these plants, disinfected in a 0.25% (w/v) mercuric chloride solution for 10 min followed by three rinses in autoclaved distilled-water. They were then established on Murashige and Skoog culture medium supplemented with 0-1 mg/L thidiazuron. Nodular callus, induced in 22-44% of all explants in T. ciliata and in 40-70% of explants in Swietenia were maintained on TDZ indefinitely and demonstrated strong, regenerative morphogenic characteristics. Shoots sprouted from six-month-old callus in the dark and T. ciliata plants could regenerate in the light. In Swietenia hybrid we obtained somatic embryo-like structures in callus derived from inflorescences. This is the first successful report of callus induction and plant regeneration from mature explants in these two important forestry species.

Kamlesh Kanwar, Anant Janrao Deshmukh, Raj Deepika, Kaushal Bindiya (India) Efficient in Vitro Rapid Axillary Bud Proliferation from Mature Terminalia chebula Retz.- A Medicinal Tree (pp 92-94)

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Original Research Paper: Efficient in vitro rapid axillary bud proliferation in Terminalia chebula Retz., a subtropical Indian medicinal tree using shoot buds from 5 yrs old tree as explants is presented. Removal of high quantities of phenolic compounds by frequent subculturing in the woody plant medium supplemented with 0.8 mg/l 6-benzylamino purine (BAP) for establishment of buds and 1.50 mg/l BAP + 0.05 mg/l naphthalene-1-acetic acid for shoot proliferation proved to be an ideal medium. This was followed by subculturing of nodal segments by removing apical buds on shoot proliferation medium for four times at an interval of four weeks to enhance shoot re-multiplication. Maximum rooting was obtained by pulsing microshoots with indole-3-butyric acid (2 mg/l) under dark for 2 hours and thereafter culturing them on half strength woody plant medium containing 0.1% activated charcoal but without any growth regulators. Roots developed within 15 days and regenerated plantlets were transferred to soil under non-sterile conditions for hardening.

Fernando Sagarra, Oscar Concepción (Cuba), Jaime A. Teixeira da Silva (Japan), Lelurlys Nápoles, Danilo Pina, Marcos A. Daquinta (Cuba) Management of Light During In Vitro Culture of Garcinia aristata (Griseb.) Borhidi (pp 95-98)

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Short Communication: Garcinia aristata (Griseb.) Borihidi seedlings growth in vitro under dark and light conditions was compared. Shoot tips and single node explants from both etiolated and non-etiolated seedlings were also compared for shoot formation. Light significantly inhibited plant height, stem elongation, the number of nodes per seedling and the protein content. However, the content of phenolics (free and cell wall-linked) and the peroxidase activity of light-treated explants at day 35 of culture were significantly higher than those observed under darkness. Interaction between light and 6-benzyladenine (BA) concentration significantly affected shoot induction. The maximum percentage of shoot formation for shoot tips and single nodes were achieved always in the dark on Murashige and Skoog culture media supplemented with 4.44 and 6.67 µM of BA, respectively. Etiolation also promoted adventitious bud regeneration on the internode segments for all concentrations of the cytokinin evaluated. This is the first report ever of the propagation of G. aristata in vitro.