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FOREST REPRODUCTIVE MATERIAL2,3

by
Marcus Robbins4

INTRODUCTION

Forest reproductive material (or germplasm) plays a vital role in forestry. Whether sexual or asexual - seeds, pollen or cuttings - it is the means by which previous generations of trees and forests produce future generations through artificial or natural regeneration. It is also the means by which their quality and quantity can be maintained or improved, and is a key source of biodiversity. Demand for seed etc. is increasing in direct proportion to regeneration programmes world-wide. In such programmes, it is essential to start with the right reproductive material, and use it properly. This article reviews some key points and developments, and serves as an introduction to FAO's new web-site5 on forest reproductive material, which will provide a framework for obtaining further information on this important topic.

SELECTION

Species and provenances: Assuming that the aims of tree regeneration are clear, and end-uses are known, the first step in getting appropriate germplasm is the selection of suitable species and provenances. The approach, strategy and methods used will depend on knowledge of the potential species' natural habitat, and existing trials. Around the world, countries continue to be involved in the underlying vital taxonomic, biological, and silvicultural studies of species and provenances. Many collaborate in networks at national, eco-regional, regional and international levels (e.g. the International Plant Genetic Resources Institute's European Forest Genetic Resources Programme (EUFORGEN), FAO's International Poplar Commission (IPC), International Neem Network (INN) and the informal network for Leucaena (LEUCNET)). Literature steadily increases on individual species, ranging from brief datasheets to detailed monographs (e.g. those produced by the Forest Research Institute/CSIRO; the Tropical Agricultural Research and Higher Education Centre (CATIE); the International Centre for Research in Agroforestry (ICRAF); the Danida Forest Seed Centre (DFSC); and the Oxford Forestry Institute (OFI). An example of a very useful compilation of such information is CAB International's Global Forest Compendium (see CABI in references). But site-specific trials that confirm species and provenance choice continue to be needed and established.

Kinds of material: Seed remains the forest reproductive material of choice. But extensive use is also made of vegetative material, as many tropical species produce seed infrequently, or are difficult to store, and therefore vegetative means may be the only way to propagate. Currently, micropropagation techniques requiring specialized material are being developed to support genetic improvement. Table 1 below summarizes current methods and materials.

Table 1: Key forest reproductive material - kinds and propagation

A CLASSIFICATION AND TERMINOLOGY
OF KEY FOREST REPRODUCTIVE MATERIAL KINDS AND PROPAGATION

TYPE OF
REPRODUCTION

INITIAL
PROCESSES

KINDS OF MATERIAL

DEVELOPMENT STAGES OR ACTIVITIES

END STAGE

NATURAL GROWTH AND DEVELOPMENT

Natural growth and development of tree
(i.e. internal reproduction)

Meristematic growth >
Differentiation of tissues

Leaves,
Stem,
Shoots,
Roots,
Flowers etc.

Growth >
Elongation >
Maturation >
Senescence >
Death

Mature tree (from which forest reproductive material is produced)

USE OF SEXUAL REPRODUCTION PRODUCTS AND PROCESSES

Natural regeneration

Flowering >
Pollination >
Fertilisation >
Fruiting >

Pollen +
Ovule >
Embryo >
Seed

Dissemination >
Germination >
Natural establishment

Seedling

Artificial direct seeding

As above

As above

Collection
Seed coating
Sowing / broadcasting

Seedling

Breeding and artificial regeneration

(Induced) Flowering >
(Artificial) Pollination >
Fertilisation >
Fruiting

Pollen +
Ovule >
Embryo >
Seed

Seed harvesting >
Nursery germination >
(Transplanting) >
(Stumping)
Planting

Seedling
(Stumped plant)
Sapling

USE OF ASEXUAL (VEGETATIVE) REPRODUCTION PRODUCTS AND PROCESSES

Natural re-growth of existing plant

Differentiation >
Growth of vegetative organs

Root Sucker,
Tuber, etc.

Elongation >
Shoot growth

Shoots

Artificially induced re-growth of existing plant

Cutting (coppicing) of stem

Tree stump

Stump coppicing >
Shoot growth

New stems or branches

Lopping (pollarding) of crown

Pollarded trunk

Pollard shoots

Re-sprouted crown

Natural regeneration of separate plants

Development of vegetative parts

Leaves,
Shoots,
or Plantule

Abscission >
Rooting >
Dissemination >
Establishment

Rooted plantlets

Macro-propagation
(Parent tree = ortet offspring = ramet,
ramets from same ortet form a clone)

Shoot cutting

Cutting

Planting >
Rooting >
(Transplanting)

Rooted cutting
(ramet)

Shoot / bud and root-stock cutting and preparation

Scion or
Bud +
Root stock

Grafting/budding >
Fusion of tissues >
Growth

Grafted tree
In-grafted branch

Branch layering

Layer

Rooting >
Severance >
Planting

Layered plant

Micro-propagation in laboratory (in-vitro)

Separation of fascicle
(conifer)

Fascicle

Rooting >
Planting

Rooted propagule

Excision of plant tissue (from meristematic tissue)

Explant

Callus formation > Treatment >
Rooting/shooting >
Development
(= Organogenesis)

Plantule
(in-vitro)

Callus formation / cell suspension
Treatment >
Somatic embryos >
Embryo development
(= Somatic embryogenesis)

Plantule
(In-vitro)

As above + Artificial coating >
Somatic (artificial) seed
Sowing >
Germination (as seeds above)

Plantule

PROCUREMENT

Once appropriate species, provenances and type of material have been determined, procurement follows, ensuring that quality (genetic, physical, physiological) and quantity are appropriate. There are many steps and factors to consider, particularly if collections are arranged direct, rather than purchasing from a dealer.

Collection requires consideration of management, logistics, and reproductive biology. Estimations of seed yield and optimum time of collection are improving as species studies provide data, but it is still an inexact science. Harvesting of seed from large forest trees continues to attract the inventive side of seed workers, and many techniques have been devised in an effort to develop effective, efficient and, above all, safe methods of tree climbing. The most successful methods use mountaineering techniques and equipment (see DFSC leaflets for example).

Seed suppliers: Commercial suppliers are increasing, and although many have built up a good reputation, quality must always be checked upon receipt. Several research or development institutions can supply material of high quality, but usually in small quantities. Directories of seed suppliers are available to guide the purchaser, such as that produced by ICRAF (Kindt, R. et al.). All reproductive material, especially material moving in international trade, should be accompanied by recognized certificates of genetic quality and physical quality, such as devised by the Organization for Economic Co-operation and Development (OECD): and the International Seed Testing Association (ISTA). Phytosanitary certificates are obligatory to ensure control of pests and diseases. Another document which is becoming mandatory, and which complements documentation on genetic and physiological quality of the seed, is the Material Transfer Agreement (MTA), mentioned below.

Handling and analysing: This part of procurement is critical for maintaining the quality of reproductive material. Activities include reception of material at the centre of operations, processing, testing, storage, treatment, distribution, and documentation. A comprehensive review of current issues can be found in Edwards (1999).

Storage: As tree seed crops are often erratic, harvesting needs to be maximized in good seed years. Seed storability is traditionally classified into two classes. Orthodox seeds store best when dried and kept cool. Recalcitrant seeds need to be kept moist and may not withstand cooling for storage. Current research indicates that these form extremes of a spectrum, and in practice there are many intermediate types. There is considerable collaborative work to improve the storability of the more recalcitrant seeds, for instance, that done by Royal Botanic Gardens, Kew, UK) and the DFSC-IPGRI Project on Handling and Storage of Tropical Forest Tree Seeds. The use of ultra-low temperatures for storage (cryostorage) is being developed for specialized reproductive material.

Testing: A good knowledge of physical, physiological, and phytosanitary quality of seed is important to monitor collection, processing, storage, distribution and to decide on techniques of propagation in the nursery. Seed laboratories (along with storage facilities) form the core of the many new dedicated seed centres that are being established nationally. Rules and regulations are available which build on experience with agricultural seed, and are used for certifying seed quality. ISTA is the leading source of information on seed analysis (see, for example, Gordon, A.G. et al. 1991).

The International Union of Forest Research Organizations (IUFRO) Research Group "Seed physiology and technology" provides effective help to exchange information on forest tree seed physiology and developments in seed technology concerned with reforestation and afforestation. See IUFRO in the references.

PROPAGATION

Nurseries: By far the commonest method of propagating new plants is in nurseries - seed is germinated to provide seedlings and young plants which are then planted out in the field. A wealth of information on techniques has been developed for many species, which are recorded in the many nursery extension manuals that have been produced. For commercial production, containerized plant systems have continued to be developed. The importance of microsymbionts is now well recognized.

Regeneration in the field: There are many instances where forests or reproductive material are regenerated or propagated in the field, outside nurseries. Natural regeneration - many silvicultural systems have been developed to help regenerate both temperate and tropical natural forests. They are being refined as reproductive ecology is better understood. However, as frequently emphasized in forestry and conservation fora, enough is known to ensure successful management - but it must be put into practice. Forest management criteria and indictors (i.e. those produced by the Centre for International Forestry Research (CIFOR)) can help monitor effects of management interventions with a view to improving such interventions over time. Direct seeding is sometimes appropriate and practiced in special cases - DFSC are currently reviewing experience. Vegetative propagation - vegetative material (e.g. cuttings) can be planted direct in the field to form plantations, individual trees, agro-forestry systems, and there has been detailed work to improved methods (see, for example, Longman 1993). A technique recently receiving attention is so-called bio-engineering, where living plants are used to stabilize or rehabilitate degraded soils or contaminated waters (e.g. Howell, J. 1999). This is not to be confused with genetic engineering.

Advanced propagation methods: Techniques of grafting and budding are well established for seed orchards. The most recent advances are in micropropagation which involves the production of plants from very small plant parts, tissues, or cells grown under strictly controlled conditions in the laboratory. The aim is to multiply material for research purposes, or as a first step in a large planting programme to rapidly increase desirable genetic stock. The techniques which have developed from tissue culture include somatic embryogenesis (i.e. regeneration of embryo-like structures from callus cell suspensions). The young plants are referred to as micropropagules. Although procedures have been successfully developed for both hardwoods and some conifers, the cost is high and it is not always certain how well the micropropagules will develop in the field. See table 1 for a summary of methods of propagation.

IMPROVEMENT

In its broadest sense, there are three aspects to improvement of forest reproductive material: conservation of sources, genetic improvement, and sustained production.

Conservation: If resources are considered valuable and/or threatened or endangered, active conservation takes two forms: In situ conservation aims to conserve genetic variation where it originated in natural stands within the range of the species or ecosystem. There are different types of conservation areas defined by forestry and conservation organizations, depending on their legal status, and objectives and intensity of management (see FAO, DFSC and IPGRI, 2001). Forest harvesting and logging carried out as an integral component of forest management, in an environmentally sensitive manner (e.g. in line with Model Code on Forest Harvesting Practice published by FAO (see FAO in references) is compatible with and contributes to maintaining biological diversity. Ex situ conservation aims to conserve genetic variation outside the natural range of the species, as individual planted trees, in clone banks or seed stands, or as reproductive material conserved in long-term storage facilities (e.g. The Millennium Seed Bank Project of the Royal Botanic Gardens, Kew, UK). New biotechnological methods have the potential for making it easier to conserve larger amounts of genetic variation for longer.

Genetic improvement starts with selection of species and provenances, through selection of individuals, to establishments of seed production areas, seed orchards, selection and development of superior clones, and various levels of controlled pollination. The most advanced stage may incorporate techniques of genetic engineering. The sequence can be summarized as in the figure 2 below:

Table 2: Different methods used in genetic improvement

Species selection

Provenance selection

Plus tree selection

Seed stand establishment

Seedling or clonal seed orchards and controlled pollination

Advanced breeding techniques

Genetic engineering

In genetic engineering, desirable genes are identified and introduced, or chromosomes are modified using biochemical techniques to remove or switch off genes controlling undesirable traits, or to introduce desirable ones. Such a process produces genetically modified organisms (GMOs), or - frequently - transgenic species. These are mentioned later.

Sustaining production: Seed production areas or seed orchards continue to be established, but many biological constraints remain. Flowering and seed production of forest trees are often erratic, and so far cost-effective methods of stimulating seed production, as in agriculture, have not been devised. Even if fruiting is abundant, actual pollination may be poor so that many seeds are empty. The actual time of seed harvest is important to ensure that seed is at its peak physiological maturity. Tackling these constraints requires a good understanding of the reproductive biology of the species.

INTERNATIONAL AGREEMENTS:

Many agreements, policies, legislation and standards have been developed that have a direct or indirect bearing on forest reproductive material and how it is used.

The Convention on Biological Diversity (CBD) - an outcome of UNCED - recognizes that forests are an important repository of biological biodiversity, and promotes conservation and sustainable use, the equitable sharing of benefits, and sets out desirable in situ and ex situ conservation measures. There are important implications for forest management, not only for conservation purposes, but also for the availability, development and use of biological resources, including forest reproductive material. The Convention recognizes national sovereignty of countries over such material, rather than being a common heritage, but calls for countries to facilitate access to material for environmentally sound use by others mainly via bilateral agreements. The practical implications of such access and benefit sharing are the subject of continuing dialogue and study in various fora and work programmes (see CBD in the references and box on COP 6 in this issue of forest genetic resources).

The Non Legally Authoritative Statement of Principles for a Global Consensus on the Management and Sustainable Development of All Types of Forests (Statement of Forest Principles) - another UNCED outcome - recognizes the importance of forest genetic material, where it affirms (in section 4) "The vital role of all types of forests.... as rich storehouses of biodiversity and biological resources and sources of genetic material for biotechnology products ...".

The legally binding International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGR) was adopted by the FAO Conference in November 2001. Its objectives are "the conservation and sustainable use of plant genetic resources for food and agriculture and the fair and equitable sharing of benefits derived from their use, in harmony with the Convention on Biological Diversity, for sustainable agriculture and food security" (Articles 5 and 6). (see separate box in this issue of Forest Genetic Resources(FGR)).

Material Transfer Agreements (MTAs), are intended to specify the range of conditions that must apply concerning access and benefit sharing by any person or organization wishing to use genetic resources, such as: purpose of access, facilitation, documentation, intellectual property rights, future availability, and national legislation. In forestry, MTAs have been in existence for a number of years in one form or other to cover forest reproductive material, and are currently used on a multi- or bilateral basis by many institutions such as CSIRO, CATIE, ICRAF, OFI, DFSC and the Millennium Seed Bank Project of the Royal Botanic Garden, Kew, UK (see article in this issue of FGR).

OECD Scheme for the Certification of Forest Reproductive Material moving in International Trade - is concerned with the certification of genetic quality of reproductive material, and has been in existence for many years. The scheme defines four broad categories of forest reproductive material: (1) Source-identified material, (2) Selected Material, (3) Qualified Material, and (4) Tested Material. and seven types of basic materials: (1) Seed Source; (2) Stand; (3) Seed Plantation; (4) Seed Orchard; (5) Parents of Families; (6) Clone; and (7) Clonal Mixture. These categories and types are used to define fourteen authorized combinations for certification. See Nanson 2001 for an overview of the new scheme. The European Union directive EU EC 105/99 on marketing of forest reproductive material is harmonized with the OECD scheme, entering into force on January 1st, 2003 in all EU countries (see article in this issue of FGR).

ISTA rules and regulations. Seed testing laboratories accredited to ISTA can issue internationally recognized certificates of seed physical and physiological quality. The rules and regulations define the conditions and tolerances required for tests of e.g. seed weight, purity, moisture content, germination and vigour. ISTA has continued to develop rules and procedures for tree seed.

SOME EMERGING ISSUES:

A number of issues have recently emerged in the forest reproductive materials field, at national or international level. Issues most likely to have an impact include:

Ownership of Forest Reproductive Material: bioprospecting

The Convention on Biological Diversity and subsequent initiatives highlight the importance of understanding ownership of biodiversity - which includes forest reproductive material. A review of the main issues has been made by Midgley and Boland, 1998. Importance is now attached to the elaboration of material transfer agreements (MTAs), which specify the terms and conditions for access and sharing of benefits. Bioprospecting is a relatively new term and describes the search for economically valuable genetic and biochemical natural resources.

Introduction of Species: alien invasives

Some introduced (exotic, foreign or alien) species have often been a success since they have been selected from a wider range of desirable forestry traits (e.g. fast growth), than was expected to be available from local (native or indigenous) species. In the majority of cases, introduced species are frequently of great economic, environmental and social value and, at times, they help sustain national and local economies; they are thus acceptable or desirable. However, such species can give cause for concern when insufficient consideration is given to the context of their use and their management. This has led to exotic species getting a bad name, and being rejected for real or perceived environmental and cultural reasons that may or may not be justified (see article in this issue of FGR about a case study on invasive alien forest tree species in Southern Africa). "Invasives", and especially "alien invasives" are now presently a political as well as technical issue. More emphasis is being given to the study, testing and use of indigenous species for planting programmes. More generally, the moving of seeds and plants as well as the increasing international trade and travel leads to greater risk of introducing insect pests, diseases or micro-organisms to new areas with sometimes fatal implications for existing ecosystems. These issues are part of the problems addressed by the concept biosecurity, which encompasses all policy and regulatory frameworks to manage risks associated with food and agriculture, including forestry (see box in this issue of FGR).

Modification of Genotypes: genetic engineering and genetically modified organisms

Genetic engineering is used extensively in some important crops in agriculture. FAO notes that genetic modification has considerable potential; however, it is not a good in itself, but a tool which must be integrated into a wider research agenda (see note on recommendations by the FAO Panel of Experts on Forest Gene Resources in this issue of FGR). In forestry, genetic modification is being tested, using techniques such as recombinant DNA and asexual gene transfer, to introduce herbicide and pest resistance, or to reduce or modify the lignin content of wood. Experiments have been carried out on several species, but are most advanced for poplar, pine and eucalyptus. FAO is launching a study of the extent of genetic modification in forest trees, which results should be available in the next issue of Forest Genetic Resources. A useful account of the pros and cons of genetic engineering, in the context of certification, is given in Strauss et al 2001. See also FAO in references.

CONCLUSION

This paper has highlighted some issues concerning forest reproductive material. Because of the central importance of seed and other material, projects and programmes have been implemented to ensure supply through institutional strengthening and capacity building. Many national seed centres have been established, in some areas linked together with regional centres (e.g. in the SADC and ASEAN regions, and Central America). Many have been a success, although sustainability is sometimes of concern. There are many opportunities in such development to incorporate participatory approaches in management and community development, thus helping to increase understanding and sharing of benefits, and to maintain access to forest reproductive material.

Because of the vital role of reproductive material in tree and forest regeneration, FAO has created a new website aimed at giving a variety of stakeholders an overview of the techniques and issues, and a practical guide to sources of further information. This article has been based on a sample of the material that will appear on the website (and eventually in a printed version). We hope you will find it useful, and look forward to comments on how to improve it to suit your needs.

REFERENCES

CABI (CAB International) - For further information on the Global Forest Compendium, visit the website: http://tree.cabweb.org/Compendium/compenfrm.asp

CBD (Convention of Biological Diversity) For the full text see the CBD website page: http://www.biodiv.org/convention/articles.asp

CIFOR (Centre for International Forest Research) Criteria and Indicators. For information, visit the website http://www.cifor.cgiar.org/

DFSC (Danida Forest Seed Centre). For full details of the publication titles, many of which are available on line, visit the website: http://www.dfsc.org

Edwards, D.G.W. Compiler. 1999. Forest Tree Seeds at the End of the 20th Century: Major Accomplishments and Needs. A State of the Knowledge Report on Forest Tree Seeds. IUFRO Unit 2.09.00 Seed physiology and technology. Available on-line at: http://iufro.boku.ac.at/iufro/iufronet/d2/wu20900/skr20900.htm

FAO:

The Model Code on Forest Harvesting Practice can be found at the following website:
http://www.fao.org/forestry/include/frames/english.asp?section=http://www.fao.org/docrep/v6530e/v6530e00.htm

For articles about biotechnology and genetically modified crops, see the following websites:
http://www.fao.org/ag/magazine/0201sp1.htm

http://www.fao.org/ag/magazine/0111sp.htm

For references on biotechnology in forestry, see under biotechnology at the Forest Genetic Resources website:
http://www.fao.org/forestry/FOR/FORM/FOGENRES/homepage/fogene-e.stm

http://www.fao.org/biotech/sector5.asp?lang=en

FAO, DFSC & IPGRI. 2001. Forest genetic resources, Conservation and management: In natural forests and protected areas (in situ). IPGRI, Rome. 90 pp.

Gordon, Dr.A.G.; Gosling, Dr.P. & Wang, Dr B.P.S. 1991. ISTA Handbook of Tree and Shrub Seed Testing, International Seed Testing Association (ISTA)

Howell, J. 1999. Roadside Bio-engineering: a reference manual, His Majesty's Government of Nepal.

ITPGR (International Treaty for Plant Genetic Resources) For the full text of the Treaty, see the website: http://www.fao.org/ag/cgrfa

IUFRO (International Union of Forest Research Organisations) Seed physiology and technology research group. Unit 2.09.00. For further information, visit the website:http://iufro.boku.ac.at/iufro/iufronet/d2/hp20900.htm

Kindt, R.; Salim, A.S.; et al. Tree Seed Suppliers Directory: Published by ICRAF (International Centre for Research in Agroforestry). Can be accessed online at:http://www.worldagroforestrycentre.org/Sites/TreeDBS/TSSD/treessd.htm

Longman, K.A. 1993 - 95 Tropical Trees: Propagation and Planting Manuals Vol 1-5, Commonwealth Science Council.

Midgley, S. & Boland D. 1998. Influences on the international exchange of forest genetic resources - An Australian Perspective. In Forest Genetics and Sustainability, edited by Csaba Mátyás,November 1999. 300 pp.

Nanson, A. 2001. The new OECD (Organisation for Economic Co-operation and Development) Scheme for the Certification of Forest Reproductive Materials, Silvae Genetica 50: 5-6.

Strauss, S.H.; Coventry, P.; Campbell, M.M.; Pryor, N.R.; Burley, J. 2001 Certification of genetically modified forest plantations. International Forestry Review 3(2):87-104.


2 Received July 2002. Original language: English.
3 This article was written as part of a consultancy by Marcus Robbins at FAO, which also included the development of a web site for information on forest seed and germplasm.
4 Independent Forestry Consultant, 119 Harefields, Oxford, OX2 8NR, United Kingdom; Email: marcus.robbins@virgin.net
5 http://www.fao.org/FORESTRY/FOR/FORM/FOGENRES/homepage/fogene-e.stm


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