1. Introduction. 2. Laboratory Organization and Equipment. 3. Media Preparation. 4. Collection, Sterilization, Excision and Culture. 5. Clonal Propagation. 6. Special Cultures. 7. Secondary Metabolite Production. 8. Pathology. 9. Nitrogen Fixation. 10. Storage of Cultures. 11. Genetic Modification. 12. Epilogue. 13. References. 14. Indices.

In Vitro Culture of Trees

Micropropagation of Woody Plants

Forest tree biotechnology

Due to the commercial importance of some conifer species, advances in conifer biotechnology often appear to overshadow equally significant advances in the biotechnology of angiosperm forest trees. However, progress with some hardwood forest trees has been just as promising as that made with conifers, and in some areas, has surpassed conifer biotechnology, particularly in the past few years. Until relatively recently, progress with in vitro propagation and gene transfer in hardwood forest trees was confined primarily to the genus Populus. Similarly, compared to other hardwood species, the greatest progress has been made both in the areas of genomics and modification of wood quality traits in this genus. However, the advances in in vitro propagation, in general, and somatic embryogenesis, in particular, have brought mass clonal propagation of other top commercial hardwood trees, in particular Eucalyptus, closer to reality and gene transfer systems have been reported for a number of them. While by far the most extensive application of genomic tools, including genomic sequencing, expressed sequence tags, transcript profiling and molecular markers, has also been made with Populus, these tools are now being applied to wider range of hardwood species. Just as with conifers, potential biotechnology applications for hardwood forest species include development of trees with faster growth, altered wood quality, and insect and disease resistance. In addition, some hardwood species are being manipulated for such non-traditional uses as phytoremediation. Given these advances and the worldwide importance of the products derived from them, it is likely that in vitro propagated and transgenic hardwood forest trees will have just as great an impact on commercial forestry and our environment as the top coniferous species.

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Hardwood tree biotechnology

A deliberate change in the growth regulators added to a tissue culture medium can elicit a dramatic response in a cultured plant. This cause-effect relationship is well-recognized, and as a result, growth regulator treatments are carefully designed based on the anticipated consequences to in vitro performance. On the other hand, decisions concerning selection of a containment vessel, or the physical status (phase) of in vitro media are frequently based on cost, availability, or convenience, without much appreciation for their broader repercussions. In fact, these underestimated variables related to the tissue culture vessel (size, shape, closure) or the medium phase (gelling agents, liquid medium, physical supports) can conspicuously modify in vitro plant behavior, often more predictably and cost-effectively than chemical additives to a medium. The potent physicochemical influences dictated by vessels & gels have frequently been cited (Chu et al. 1993; Fujiwara and Kozai 1994, this volume; Kozai et al. 1992; Obeidy and Smith 1990; McClelland and Smith 1990; Smith and McClelland 1991), paving the way for practical management of these tools to optimize tissue culture systems. Many tissue culture laboratories still operate with the assumption that vessels, gels, and related variables are minor players in development of new in vitro strategies, in spite of ample evidence that these underrated variables exert considerable leverage on in vitro productivity, and warrant more comprehensive description and interpretation.

M. Barghchi

Papers

Mass clonal propagation in vitro of Robinia pseudoacacia L. (Black locust) cv. ‘Jaszkiseri’