by
Rowland D. Burdon
NZ Forest Research Institute
Private Bag 3020
Rotorua
New Zealand
INTRODUCTION
Biotechnology is an area where spectacular advances have been made and are continuing to be made. This area includes: new methods of vegetative propagation, including in vitro systems; cryopreservation; greatly increased regulation of flowering; and molecular biology which includes locating and applying DNA markers, and carrying out genetic transformation.
Given the constraints traditionally imposed by the long life cycles and physical size of trees, plus the limited cross-fertility between many related species, the use of biotechnology for genetic improvement looks particularly attractive. New and improved systems of vegetative propagation can help greatly, allowing inter alia more rapid delivery of genetic gain by mass propagation of improved material. Complete control of flowering and control of maturation state would help greatly in numerous ways. Satisfactory systems of genetic fingerprinting will be a welcome aid to breeding and conservation. There is the prospect of new methods of selection, especially reliable early selection of very young forest trees which is often particularly difficult to achieve. ‘Genetic engineering’, which is usually equated with genetic transformation, offers the prospect of types of genetic improvement that would not otherwise be available.
The availability of new technology obviously presents great potential opportunities, but it also poses problems which need to be recognised. It entails a new set of decisions on allocation of resources, on management structures, and even on institutional matters. All such decisions create possibilities for mistakes. Some mistakes are inevitable in the course of progress, but many can be avoided by a careful examination of the issues.
CAPABILITIES AND REQUIREMENTS
While biotechnology can provide a new set of very powerful tools, it is appropriate to weigh the conditions that are needed for these tools to be used advantageously and safely.
New vegetative propagation technology (cuttings, tissue-culture plantlets or embryogenetic culture) can greatly accelerate the delivery of gain. Reversal of maturation (physiological aging) or control of maturation by cryopreservation can help secure genetic gain in the face of what is often a frustrating biological constraint. The genetic gain, however, is dependent on having (or recreating) genetic variability to work with, and carrying out effective screening and selection.
There is the prospect of using new biotechnology to give more complete control of flowering. Induction of extremely precocious flowering in pines and other genera, as can already be achieved with various members of the Cupressaceae, could remove an important breeding constraint. The value of such a measure, however, would depend on having appropriate genetic material on which to use it.
Genetic fingerprinting, using DNA technology, can be used inter alia to characterise populations and help evaluate the amount of genetic variation within and between populations. This has special value for examining genetic resources that form the base populations for tree breeding. For such a role, DNA markers, particularly the convenient PCR-based markers, can be far more powerful and precise than the by now traditionally-used isozymes. The research required to develop the use of such markers, however, will need to be carried out on appropriate population samples, and to obtain such population samples will usually entail having available appropriate gene resources for a classical breeding programme.
The detection of quantitative trait loci (QTL) promises new capabilities for evaluating candidate genotypes. It could offer an especially powerful tool for early selection, which at present is often unreliable to the extent of being a major limiting factor in achieving genetic gain per unit time. In the case of advanced-generation hybrids between species the use of markers linked to QTL offers the prospect of more efficient assembly of the best features of each of the parent species. Identification of linkages, however, requires gene mapping and QTL dissection. To achieve that within outbreeding species, in which there is little genetic linkage disequilibrium between markers and QTL, will entail producing and evaluating large control-pollinated progenies, with specialised mating designs. Moreover, the process of validating the early selection will require good progeny trials that are followed up over a long period.
Genetic transformation will, as mentioned earlier, offer potential gains that can be qualitatively different from those achievable by conventional breeding. These include resistance to environmentally benign herbicides, or male (and possible female) sterility. The sterility may become or remain a regulatory requirement for the release of Genetically Modified Organisms, it holds promise for greater wood production through reduced diversion of primary biomass within improved individuals, and in many situations it could greatly facilitate the management of genetic resources on a scale too large to allow routine controlled pollination.
However, the initial testing of transformants will need to be thorough and prolonged, to ensure that there are no disastrous side effects such as the corn blight susceptibility that arose in maize after using a particular male-sterility factor for producing hybrid corn (Levings 1989)1. The types of transformation that seem less risky, notably the use of ‘anti-sense’ DNA, are likely to require even more elaborate development work than the insertion of DNA sequences alien to the species. Transformant cultivars will need to be based on genetic material that has been improved in basic silvicultural features; such ‘background’ improvement, which cannot all be achieved by genetic engineering, will need to continue and will be dependent on maintaining much of the natural genetic variability. Moreover, the transformants that are used will still need to constitute a population with sufficient genetic diversity to avoid undue crop vulnerability.
The various preconditions spelled out above for satisfactory development and application of biotechnology effectively add up to essentially the full infrastructure of classical breeding measures, which include conserving or assembling, and maintaining genetic resources, crossing, and field testing and evaluation. Furthermore, there will be the costs of both the development and routine application of the biotechnology. The costs will be considerable; each aspect of biotechnology can be expensive to develop in itself, strong interdependence can exist between aspects (e.g. the dependence of genetic transformation on good in vitro propagation technology), and there will be the inevitable failures or obsolescence of some avenues of biotechnology.
FUNDING ISSUES
The implications for funding policy are clear. Biotechnology, if embraced, must be applied in addition to classical breeding measures and not in place of them. Well into the future, there will doubtlessly be aspects of breeding where biotechnology may save much of the time and resources that now have to be devoted to classical breeding. In the short term, however, the opposite will generally be true.
The adverse consequences of a premature adoption of biotechnology, at the expense of developing and maintaining a classical hierarchy of breeding populations and other genetic resources, could be threefold. First, it can sacrifice genetic gain that is available in the short term from classical breeding measures. Such gains from classical breeding are often very large and rapid, particularly with newly-introduced exotic or other recently domesticated species. The gains may be the products of large investments that have already been made but which require follow-up work for the payoffs to accrue. Second, if the classical breeding infrastructure is under-resourced most of the potential benefits of biotechnology may be captured belatedly or not at all. Third, if a switch in resources occasions a depletion of natural genetic variability it could even lead to biological disasters which could be much exacerbated by injudicious use of biotechnology.
Investment decisions concerning biotechnology in relation to classical breeding can pose a dilemma. While the potential costs and risks, which I have mentioned above, of shifting resources away from classical breeding are considerable, opting out of new biotechnology is an unattractive option. There is the obvious risk of being left in a technological backwater, and if the funding is being switched into biotechnology regardless, those who stand firm by a commitment to classical breeding measures could be left with little or no funding support. Even if support continues an ‘image problem’ can arise. In the longer term, there is the spectre of being left at a commercial disadvantage through competitors having a superior product, with the advantages accruing from such a product being secured by intellectual property rights. Even without the actual commercial pressures it can be frustrating, with stagnant or falling funding levels, to see opportunities for new and exciting science which could only be pursued to the detriment of a well-designed operational breeding programme.
A RESOLUTION ?
The hope is that investment in biotechnology will indeed be made as an addition to classical breeding work. The prospective benefits, plus the perception that higher returns are likely to be available, may well attract support from additional pools of funds. That is highly desirable, but the situation will still require careful management. Biotechnology and classical breeding will need to be properly integrated, which will certainly be easier if the funding arrangements are conductive to collaboration. An emphasis on proprietary technology, while it may favour funding, can bring some problems; one is an insulation from adequate peer reviews of proposals and findings. Another could be uncoordinated genetic management to the detriment of the future value of genetic resources. Also the adoption of proprietary technology may not fit comfortably with the collaborative nature of existing tree breeding cooperatives which are of proven value. Furthermore, an emphasis on proprietary technology may not fit well with the total costs entailed; a properly balanced programme of biotechnology, which recognises the interdependence among different aspects of the technology and covers the risk of failure or obsolescence of individual technologies, may be too expensive for any one organisation to mount. Other problems involve the relationships between countries to whom the gene resources are indigenous, but whose capital resources are inadequate for their development, with wealthier interests that are attracted by the prospects of proprietary technology. Some of the problems, however, are addressed by the FAO's Internal Undertaking on Plant Genetic Resources (FAO 1983); and, more recently, by the International Convention on Biodiversity (Anon 1992), which is necessarily compromise between different interests. Hopefully, it will work.
CONCLUSION
Appropriate allocation of resources to biotechnology and classical breeding will not of itself ensure the right outcome, but it is a crucial prerequisite for it. The clear message is that, at least in the short to medium term, the adoption of new biotechnology must be part of a substantially increased commitment to the genetic improvement of forest trees, rather than a switch of effort away from classical breeding measures. The adoption of new biotechnology is ipso facto a commitment to greater domestication. Yet domestication is all about making increased management inputs in order to obtain better returns from managing and utilizing organisms for human benefit. To this principle, the use of advanced biotechnology for the improvement of forest trees can be no exception.
ACKNOWLEDGEMENTS
I thank Drs S.D. Carson and D.R. Smith for constructive criticism of the draft.
GENERAL REFERENCES
Anon (1992). Convention on Biological Diversity. United Nations Conference on Environment and Development. (Secretariat of the Convention on Biological Diversity, 11, Chemin des Anémones, B.P. 76, CH-1219, Châtelaine, Switzerland).
Burdon, R.D. (1992). Tree Breeding and the New Biotechnology - in Damaging Conflict or Constructive Synergism? "Pp 1–7 (keynote address) in “Resolving Tropical Forest Resource Concerns through Tree Improvement, Gene Conservation and Domestication of New Species” (1993). Proceedings of IUFRO Conference (Section S2.02–08) held October 9–18 1992 in Cartagena and Cali, Colombia. (CAMCORE, North Carolina State University, Box 7626, Raleigh, North Carolina 27695-7626 USA). 468 pp. (E)
FAO (1983). International Undertaking on Plant Genetic Resources. Resolution 8/83 of the 22nd Session of the FAO Conference, Rome 5–23 November 1983. FAO, Rome.
Haines, R.J. (1993). The Role of Biotechnologies in Forest Tree Improvement, with Special Reference to Developing Countries. FAO Forestry Paper 118. FAO, Rome.
Haines, R.J. (1994). Biotechnology in Forest Tree Improvement: Research Directions and Priorities. Unasylva 177:46–52.
Kanowski, P.J. (1993). Forest Genetics and Tree Breeding. Forestry Abstracts 63:717–26.
Libby, W.J. (1991). The Problem of Biotechnological Constipation. Pp 323-8 in Woody Plant Biotechnology (ed. Ahuja, M.R.) Plenum Press, New York, USA.
Forest Genetic Resources No. 22. FAO, Rome (1994)
This article was adapted by the author from a keynote address presented at the IUFRO meeting “Resolving Tropical Forest Resources Concerns through Tree Improvement,
Gene Conservation and Domestication of New Species” held 9–18 Oct. 1992, Cali, Colombia.
1 Levings, C.S. III (1989). Science 250:942 7.
