Protocol For Somatic Embryogenesis In Woody Plants

World population is increasing at an alarming rate and this has resulted in increasing tremendously the demand for tree products such as wood for construction materials, fuel and paper, fruits, oils and medicines etc. This has put immense pressure on the world’s supplies of trees and raw material to industry and will continue to do so as long as human population continues to grow. Also, the quality of human diet, especially nutritional components, is adversely affected due to limited genetic improvement of most of fruit trees. Thus there is an immediate need to increase productivity of trees. Improvement has been made through conventional breeding methods, however, conventional breeding is very slow due to long life cycle of trees. A basic strategy in tree improvement is to capture genetic gain through clonal propagation. Clonal propagation via organogenesis is being used for the production of selected elite individual trees. However, the methods are labour intensive, costly, and produce low volumes. Genetic gain can now be captured through somatic embryogenesis. Formation of embryos from somatic cells by a process resembling zygotic embryogenesis is one of the most important features of plants. In 1958, Reinert in Germany and Steward in USA independently reported somatic embryogenesis in carrot cultures. Since then, tremendous progress in somatic embryogenesis of woody and non-woody plants has taken place. It offers a potentially large-scale propagation system for superior clones.

World population is increasing at an alarming rate and this has resulted in increasing tremendously the demand for tree products such as wood for construction materials, fuel and paper, fruits, oils and medicines etc. This has put immense pressure on the world’s supplies of trees and raw material to industry and will continue to do so as long as human population continues to grow. Also, the quality of human diet, especially nutritional components, is adversely affected due to limited genetic improvement of most of fruit trees. Thus there is an immediate need to increase productivity of trees. Improvement has been made through conventional breeding methods, however, conventional breeding is very slow due to long life cycle of trees. A basic strategy in tree improvement is to capture genetic gain through clonal propagation. Clonal propagation via organogenesis is being used for the production of selected elite individual trees. However, the methods are labour intensive, costly, and produce low volumes. Genetic gain can now be captured through somatic embryogenesis. Formation of embryos from somatic cells by a process resembling zygotic embryogenesis is one of the most important features of plants. In 1958, Reinert in Germany and Steward in USA independently reported somatic embryogenesis in carrot cultures. Since then, tremendous progress in somatic embryogenesis of woody and non-woody plants has taken place. It offers a potentially large-scale propagation system for superior clones.

World population is increasing at an alarming rate and this has resulted in increasing tremendously the demand for tree products such as wood for construction materials, fuel and paper, fruits, oils and medicines etc. This has put immense pressure on the world’s supplies of trees and raw material to industry and will continue to do so as long as human population continues to grow. Also, the quality of human diet, especially nutritional components, is adversely affected due to limited genetic improvement of most of fruit trees. Thus there is an immediate need to increase productivity of trees. Improvement has been made through conventional breeding methods, however, conventional breeding is very slow due to long life cycle of trees. A basic strategy in tree improvement is to capture genetic gain through clonal propagation. Clonal propagation via organogenesis is being used for the production of selected elite individual trees. However, the methods are labour intensive, costly, and produce low volumes. Genetic gain can now be captured through somatic embryogenesis. Formation of embryos from somatic cells by a process resembling zygotic embryogenesis is one of the most important features of plants. In 1958, Reinert in Germany and Steward in USA independently reported somatic embryogenesis in carrot cultures. Since then, tremendous progress in somatic embryogenesis of woody and non-woody plants has taken place. It offers a potentially large-scale propagation system for superior clones.

This volume provides an overview of methods for plant species, mainly species with high economic value, to achieve in vitro propagation through somatic embryogenesis. Chapters guide readers through somatic embryogenesis protocols, somatic embryos in plants, and new methodologies that are used out to solve in vitro recalcitrance of many species to this morphogenetic route. Written in the format of the highly successful Methods in Molecular Biology series, each chapter includes an introduction to the topic, lists necessary materials and reagents, includes tips on troubleshooting and known pitfalls, and step-by-step, readily reproducible protocols. Authoritative and cutting-edge, Somatic Embryogenesis: Methods and Protocols aims to guide future researcher to achieve success in obtaining and regenerating somatic embryos. Chapter 6 is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.

The rapid progress made on somatic embryogenesis and its prospects for potential applications in improving woody plants prompted us to edit this book initially in three volumes, and now to add two more volumes. The editors were all convinced that such a treatise was needed and would be extremely useful to researchers and students. This Volume 4 has been divided into three sections and contains 23 chapters. Section A contains eleven chapters covering studies of embryo development and cell biology of white spruce, proliferative somatic embryogenesis in woody species, somatic embryo germination and desiccation tolerance in conifers, performance of conifer somatic seedlings, apoptosis during early somatic embryogenesis, water relation parameters in conifer embryos, image analysis of somatic embryos, somatic embryogenesis in woody legumes, cold storage and cryopreservation, and commercialization of plant somatic embryogenesis. Section B contains six chapters dealing with angiosperm woody plants, such as somatic embryogenesis in myrtaceous plants, Laurus nobilis, Simarouba glauca, Magnolia spp., Juglans cinera, and somatic embryogenesis and evaluation of variability in somatic seedlings of Quercus serrata by RAPD markers. The chapters contained in Section C are focused on somatic embryogenesis in gymnosperms, including Pinus patula, Encephalartos, Picea wilsonii, Pinus banksiana, hybrid firs, and Taxus. All the chapters have been peer-reviewed and revised accordingly to improve their quality.

These books provide an update to progress on somatic embryogenesis in woody plants including both angiosperm and gymnosperm trees. In the past, most of the information on this subject was scattered in proceedings volumes, journals, biotechnology books, etc. It has been difficult for the researchers and students to obtain comprehensive information on this rapidly growing subject from a single source. These books enable readers to get a clear view of this subject on historical, anatomical, physiological, biochemical and molecular aspects, and applications including protoplasts, cryopreservation, manufactured seed (artificial seed), genetic transformation, bioreactors, mutations, and future uses in forest plantations. Each selected woody plant mentioned in the book is briefly introduced first, covering botany and genetics, importance and geographical distribution, breeding problems, and in vitro propagation and problems of each selected woody plant and then is followed by the description on the initiation and maintenance of embryogenic cultures, embryo development and germination, and field trials (if any) of these plants. These books are meant for graduate students and researchers in forestry and horticulture as well as biotechnologists.

The quality of human life has been maintained and enhanced for generations by the use of trees and their products. In recent years, ever rising human population growth has put a tremendous pressure on trees and tree products; growing awareness of the potential of previously unexploited tree resources; and environmental pollution have both accelerated the development of new technologies for tree propagation, breeding and improvement. Biotechnology of trees may be the answer to solve the problems which can not be solved by conventional breeding methods. The combination of biotechnology and conventional methods such as plant propagation and breeding could become a novel approach to improving and multiplying a large number of the trees and woody plants. So far, plant tissue culture technology has largely been exploited by commercial companies in propagation of ornamentals, especially foliage house plants. Generally, tissue culture of woody plants has been recalcitrant. However, limited success has been achieved in tissue culture of angiosperm and gymnosperm woody plants. A number of recent reports on somatic embryogenesis in woody plants such as Norway spruce (Picea abies), Loblolly pine (Pinus taeda), Sandalwood (Santalum album), Citrus and mango (Mangifera indica), offer a ray of hope for inexpensive clonal propagation for large-scale production of plants or 'emblings' or somatic seedlings; protoplast work; cryopreservation; genetic transformation; and synthetic or artificial or manufactured seed production.

Micropropagation has become a reliable and routine approach for large-scale rapid plant multiplication, which is based on plant cell, tissue and organ culture on well defined tissue culture media under aseptic conditions. A lot of research efforts are being made to develop and refine micropropagation methods and culture media for large-scale plant multiplication of several number of plant species. However, many forest and fruit tree species still remain recalcitrant to in vitro culture and require highly specific culture conditions for plant growth and development. The recent challenges on plant cell cycle regulation and the presented potential molecular mechanisms of recalcitrance are providing excellent background for understanding on totipotency and what is more development of micropropagation protocols. For large-scale in vitro plant production the important attributes are the quality, cost effectiveness, maintenance of genetic fidelity, and long-term storage. The need for appropriate in vitro plant regeneration methods for woody plants, including both forest and fruit trees, is still overwhelming in order to overcome problems facing micropropagation such as somaclonal variation, recalcitrant rooting, hyperhydricity, polyphenols, loss of material during hardening and quality of plant material. Moreover, micropropagation may be utilized, in basic research, in production of virus-free planting material, cryopreservation of endangered and elite woody species, applications in tree breeding and reforestation.