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African Journal of Traditional, Complementary and Alternative Medicines
African Ethnomedicines Network
ISSN: 0189-6016
Vol. 1, Num. 1, 2004, pp. 4-14
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African Journal. Traditional, Complementary and Alternative Medicines Vol. 1, Num. 1, 2004, pp. 4- 14
Invited Review
CONSERVATION OF PLANT GENETIC RESOURCES
Omotoye Olorode
Department of Botany, Obafemi Awolowo University Ile-Ife. Nigeria. E-mail:omotoopo@yahoo.com
Code Number: tc04002
Abstract
Survey, collection and conservation
are important starting points in the genetic resources impact chain and in
sustainable environmental protection strategies. Collection of plant genetic
resources provides materials for herbaria, field gene banks, seed banks and in
vitro conservation which are all important and crucial for characterisation
and evaluation of plant genetic resources for various human needs. Because
only a small spectrum of genetic variability is apprehended during collections, in
situ conservation is crucial for optimizing biodiversity conservation
programmes.
Keywords: Conservation, germplasm, cultivated plants, genetic resources
Introduction
This contribution is being made
at the conjuncture of sustained national, and especially international, build-up
concerning the antecedents, regarding the growing awareness on environment
and biodiversity include the preservation of environment and conservation
of plant and animal genetic resources and biodiversity generally. The origins
of this concern and the contributions by scientists and institutions towards
this concern were reviewed by Olorode (1995, 1995a). Some of the relevant
work are the ones by Hardin (1968), Iltis (1968), Iltis et al. (1970),
Odum (1971), Ophuls (1977), Hawkes (1990), Kokwaro (1994) and Lesser (1994).
Since man started domesticating plants and animals about 10,000 years ago, technology
and increased human population have put consistent pressure on the habitats
of plants and animals. This had resulted in progressive diminution of biodiversity.
More importantly, the growth of population, agriculture and industry in Europe
and the Americas in the last millennium not only destroyed habitats (and biodiversity),
it narrowed down the genetic diversity of crops. Great political and economic
events that since had significant global impact such as the voyages of discovery,
the search for the sea route to the east, the slave trade, colonialism, major
population movements, wars ("hot"and "cold"), were
influenced, triggered or accompanied by the ascendancy of certain crops. The
major ones among these crops were rubber, cotton, tobacco, sugar cane, cocoa,
breadfruit, bananas, various spices, coffee, maize, wheat, Irish potato and
oil palm. Major and long-distance germplasm movements were involved (Drodziak,
1982; Juma, 1989). Similarly, contemporary global events such as commercial
large-scale agriculture, corporate control of agriculture and food, corporate
control of agricultural inputs, the major crop successes and crop failures,
also have their roots in the control of genetic resources and biotechnology
(Fedder, 1976; George, 1970; Mooney, 1983; Juma, 1989; Lesser, 1994; Sachs,
1995).
The events and developments referred to above occurred and are occurring within
the context of the dialectics of the imperatives of international cooperation
and the reality of the sovereignty of individual nation states and peoples
whose interests may conflict or coincide. These conflicts (contradictions)
or identities have become heightened by the increasing resource gap between
the rich countries and the poor countries of the world. In this regard, the
areas of the exploitation of genetic resources, technological capacity for
their conservation and utilization, and the controversies surrounding intellectual
property rights (IPR's) and the ownership of genes in natural populations
(Juma, 1989; Crespi, 1990; Lesser, 1994; Olorode, 1995a) must form appropriate
background for all our deliberations.
In concluding this introduction, the clarification, if not apologia, needs to
be made ab initio about the generalized character of this contribution
given the specific thrust of the African Journal of Traditional Complimentary
and Alternative Medicines. The main reason for this approach is simply
that most plants used in "traditional" medicine remain wild and
are sourced, therefore, from their natural habitats which are disappearing
rapidly. To give an example, in a most recent collection of plant species (Hollist,
2004) used by the Yoruba (of Nigeria) in oral and dental medicaments, only
37 out of the entire 138 species (i.e. about 25%) mentioned are cultivated or protected (i.e.
not deliberately cultivated) in farm lands or home gardens; the overall percentage
of cultivated "traditional medicine" plants are certainly
much lower. In any case, even when some of these plants are cultivated or protected,
most of the herbal supply of traditional medicine is still from the wild.
As we emphasize below, even for those cultivated or protected species or taxa,
only a limited segment of the genetic variability can be so conserved! The
second reason for the generalized approach of this contribution is that hitherto-unknown
or little-known traditional medicinal properties of Nigerian (African) plants
are disseminated and popularized quite frequently. Consequently a generalized
conservation strategy is a sort of "comprehensive insurance" that
will forestall the complete loss of these potential remedies. Thirdly, a conservation
strategy that preserves the plant communities (the evolutionary milieu) of
our target species is more scientific and more rational (Janzen, 1980; Daniels et
al., 1996; Jones et al., 1994)
Conceptualising Collection and Conservation
The twin processes of collection
and conservation can be conceived in different ways depending on the biological
material concerned or the priorities that are set. We need to clarify these
nuances.
One consequence of collection and conservation is to remove (collect) genetic
material from the milieu in which it evolved and perpetuate it in a different
milieu (in laboratories, ex situ field gene banks, botanical gardens
etc). This is perhaps the most common consequence (and goal) of most crop germplasm
collections and expeditions and collections of medical culture and general
microbial germplasm collections (Hawkes, 1990; Dasilva, Kalakoutskii and Da-Kang,
1990; Seeliger 1990; Ng, 1991; Ruredzo and Hanson, 1991; Okoli, 1991).
In the case of medical culture collections and general microbial germplasm collections
and conservation, the consequence (and the goal) identified above is given.
This is because the original sources of the materials are sporadic and the
germplasms are, almost invariably, not amenable to in situ conservation
because of economic and other considerations. It seems however that the attitudinal
and practical basis of collection and conservation (ex situ) of crop
(or any "useful" plant) germplasm is more complex. The threat of
genetic erosion is a real one arising from destruction of habitats and biodiversity
necessitating a "rescue strategy" for germplasm collection and ex
situ conservation. The main conceptual concern here is that collection
and conservation in the way "gene hunters" understand them may become
the pivot for neglect of in situ conservation and promotion of the illusion
that we have a store of biodiversity in our "gene banks"(Moore,
1990; DaSilva et al., 1990; Ng, 1991)
It is on the basis of the above that Olorode (1995a) conceptualized the scope,
priorities and strategies for dealing with the task of conservation of plant
genetic resources in developing nation states like Nigeria and the role of
national institutions like NACGRAB, national research institutes, FEPA, the
universities, communities and NGO's. The aim of the present paper is
to dilate on these issues in respect of the specific areas of collection and
conservation of plant genetic resources.
Collection of plant Genetic Resources
As we noted above, collection
and conservation are not separate processes in collection of medical cultures
and microbial germplasm. Consequently Seeliger (1990) stated that:
"The main aim of collection is the deposition of comparative material
under proper conditions in order to prevent its destruction, decay, decomposition,
morphological change, alteration or loss of biochemical ….. serologic
and toxic properties, or change in its susceptibility to biostatic and biocidal
agencies…. kept under the exact condition of its first isolation".
On the contrary collection of materials of higher plants of different ecological
or utilitarian categories may be either for purposes of record in herbaria,
for rehabilitation in field gene banks or botanical gardens or for long-term
preservation as seeds or in vitro cultures.
In this presentation, emphasis is on collection of higher-plant genetic resources.
The most cost-effective strategy for carrying out the task of collection and
exploration is to do so with the aim of collecting herbarium materials, live
specimens and propagules (seeds, tubers, suckers, etc)
What is to be collected?
Olorode (1995a) noted the tendency
for PGR collectors (Okojie and Okali 1993, Attere et al. 1991) to
concentrate almost exclusively on the germplasms of crops and their relatives
(or the so-called useful plants). It was emphasized, as some other workers
did (Juma, 1989; Lusigi, 1991; Ndambuki, 1991), that from a scientific and
ecological point of view, such tendencies are short-sighted. We hasten to
admit as Hawkes (1990) did, that these tendencies are forced on researchers
partly because of the conceptual limitations and impatience of policy makers
and funding agencies.
A comprehensive approach to the question needs to be adopted. Consequently the
approach to what is to be collected must be environmentally sound. It must
focus attention not only on germplasm that have potential use but those that
sustain the habitats in which the "useful"plants evolved. Seven
categories of the target groups were identified by Olorode (1995): cover crops
for soil protection and reclamation including grasses, shrubs and trees; dominant
species especially in the savanna (Daniellia oliveri (Rolfe) Hutch.
and Dalz., Anogeisus leiocarpus (DC) Guill. and Perr. , Terminalia L. spp., Combretum Loefl. spp., Pilliostigma Hochst. spp.
etc.); fodder species and range grasses; wild fruits; wild leaf vegetables;
cultivated plants and their wild relatives (van Soest, 1990); ornamental and
decorative plants. The collection of dominant species as suggested herein should
provide material for studies in their phenology, regeneration and reproductive
biology all of which will be crucial for the habitat rehabilitation programme
which is proposed below as part of conservation strategy.
Where and how to collect?
For every category of germplasm
that is adjudged to be desirable for collection, the guiding principles are
that collections be exhaustive in populations and comprehensive in their
range of geographical and eco-geographical distribution. Collection in the
entire range of geographical distribution ensures that the totality of the
genetic response of organisms to the environments they have confronted are
sampled while exhaustive collections in populations ensure that the responses
of genetic systems in local populations are apprehended.
It should be quite easy to appreciate the fact that explorations, for practical
reasons, have traditional routes and that collections tended to be done
largely along those routes: this limits the range of collections. Consequently
collection efforts need to be directed towards the areas in which considerable
vegetation fragmentation have not taken place and from which collections have
been rare. In the present situation of Nigeria in which previous collections
have been for herbaria rather than conservation, collection along traditional
routes and more obscure routes need to be undertaken.
As a general rule, we can adopt a strategy in which collections are done in
each vegetation belt, in as many ecosystems as practicable and in representative
communities. At the level of individual species populations, attention needs
to be paid to population size as this affects genetic variability and the consequences
of stochastic population
processes (Lusigi, 1991). As noted above collections need to be done so that
many purposes are satisfied-herbaria records, life ex situ gene
banks and seed bank requirements. The traditional records for collections must
accompany each collection-collector, collector(s)' number, latitude/longitude,
locality, soil, community composition, prevalent fauna (if data is available),
soil and edaphic condition, local uses, flowering period, fruiting period etc.,
abundance of the specimen etc. In the case of cultivated plants, name of donour
(s), size (acreage) of farms and for how long the germplasm had been sustained,
original source of materials need to be ascertained (Martin, 1995).
Before collection and exploration
Explorations and collection strategies
and plans can profit considerably from preliminary surveys. Indeed surveys
represent the starting point of genetic resources impact chain (Hawkes, 1990).
Once target groups to be collected are identified, a survey of previous collections
from flora, herbaria, monographs and other published works should be done.
This provides baseline information on what is known - what variations
exist, what localities had been explored, time of flowering and fruiting, abundance,
origins of the materials, genetic structure of populations, taxonomic problems
etc.
In general regard to the above it is necessary to state a point made elsewhere
(Olorode 1995a) that various fragmental but important information exist at
various levels of work already done on Nigerian flora, but which are mutually
unknown to workers in different parts of the country. Some insight into this
issue can be gained from published work on various topics (Nwankiti, 1976;
1976a; Olorode and Baquar, 1976; Omidiji, 1980; Morakinyo and Olorode, 1984;
Omaliko and Ene-Obong, 1988; Faluyi, 1990; Faluyi & Nwokeocha, 1993; 1993a;
Okojie and Okali, 1993). Some of these will be useful as part of preliminary
survey towards profitable collection and exploration efforts.
Conservation of Plant Genetic Resources
Earlier on in this paper, the
two main strategies of conservation (in situ and ex situ strategies)
have been identified and partly appraised. These issues are further addressed
in this section. But because of the urgency of needs, commercialization and
profit, conservation of plant genetic materials tends to be driven almost
entirely by raw utilitarianism. Consequently, conservation programmes are
generally selective in terms of target taxa or groups of taxa. One consequence
of this tendency is that the conception of the conservation of the so-called
useful plants go the way of dominant crops and domestic animals. Monocultures
are encouraged with all the debility of progressively narrowed genetic base.
An issue that is closely related to the dominance of utilitarianism is the question
of the production and expansion of broad knowledge base in plant collection,
identification, herbarium management, and general taxonomic studies. The acquisition
and expansion of knowledge in these areas are pivotal long-term imperatives
for scientific and forward-looking policies in conservation of plant genetic
resources. The training of scientists (the so-called "pure"scientists)
and technical personnel in these areas are therefore necessary for understanding
and conserving taxa whose use-values may exist only in the future.
In situ Conservation
Genetic materials are conserved in
situ when they are maintained in their original self-perpetuating populations
(Moore, 1990). The importance of in situ conservation even within
narrow utilitarian apprehension of enthusiasts of crops improvement, is
captured succinctly in the surmise by Ingram (1990) that:
"Even if all the optimistic predictions of bioengineers are correct and
virtually all genetic material can eventually be easily synthesized, we will
need to be studying and learning from successful populations in diverse ecosystems
on an on-going basis"
and by Moore (1990) that:
"Ex situ storage in gene banks, botanic gardens and zoos can only
provide a tiny proportion of data and material derived from self-perpetuating
populations and demands for new genetic diversity outstrip the breeders'ability
to produce".
But beyond serving as a means of replenishing and augmenting the genetic system
of agricultural crops and other categories of useful plants, the complexity
of natural biomes and ecosystems ensure the stability of terrestial ecosystems
including that of agricultural ecosystems. Clearly complexity and stability
are best maintained through in situ conservation (see Lusigi, 1991).
Conservation in reserves and parks
In implementing the programmes
of in situ conservation, the question is about how much human interference
or "management" will be permitted or allowed. The capacity of
policy-makers to implement conservation strategies will depend on social,
political and economic factors. The point consequently is to balance these
factors.
According to Lusigi (1991) ten categories of protected areas (natural ecosystems)
are recognized according to a system developed by the International Union for
Conservation of Nature and Natural Resources (IUCN). These categories represent
various levels of protection from human interference. In the case of biosphere
reserves for example, areas of representative terrestrial and coastal environments
are recognized for purposes of protection under the UNESCO Man and Biosphere
(MAB) Programme. Strategies of conservation in the MAB Programme combine "conservation
and sustainable use of natural resources" (Ingram 1990) i.e. it involves
human management of these reserves (Sanford et al. 1982).
From what we have said about the importance of in situ conservation,
it is obvious that very definite effort must be made to appraise the status
of various nature reserves and natural parks in Nigeria with a view to strengthening
them as conservation areas. Similarly various assaults on natural vegetation
by emergency large-scale commercial farmers have destroyed large acreages of
natural vegetation all over Nigeria. Many species and varieties of plants and
animals are probably lost for ever. In the oil-producing areas, the tragedy
is beyond description. It is a pity of incredible proportions that in the face
of irresponsibility of political decision-makers, scientists have either kept
quiet or they are actively collaborating. The questions of Environmental Impact
Assessments of projects and Industries need to be popularized and ingrained
in public consciousness; scientists and conservationists must lead this process.
Some sorts of reparation scheme may have to be put in place against organizations
and individuals that have destroyed massive amounts of natural vegetation.
Public Institution lands as nature reserves and germplasm rehabilitation
centres
It should be possible to utilize
undisturbed and unused land spaces in certain public institutions at national,
state and local government levels as conservation and rehabilitation centers.
Local communities can, and should, be variously mobilized to participate
in, and even initiate and design, these processes.
The idea of rehabilitation of natural vegetation in certain locations may sound
strange but the concept is viable. In all locations in our country naturalists
have some idea of the history of the vegetation. With institutional support
and systematic mobilization of Community Based Organisations (CBOs), the plant
materials that have been removed or have disappeared can be sourced and replaced.
This is possible with some ideas of the history of the vegetation structure
and cover patterns in these areas.
Ex situ Conservation
Ex situ strategies of conservation
involve preservation of genetic resources outside their natural habitats.
These strategies are more attractive to plant breeders and plant improvement
organizations. They are usually plant genetic materials with immediate or
near immediate use value in plant improvement.
Ex situ germplasm conservation is done in live gene banks (botanical
gardens, home gardens, horticultural centres and field gene banks in research
stations), as stored seeds in conventional seed banks, or as in vitro storage
of plant tissue (buds, meristems, calluses etc). In Nigeria, apart from educational
institutions (universities etc) and research institutions and centers (with
specific crop mandates), life ex situ gene banks in form of botanical
gardens hardly exist although in city centers, commercial horticultural outfits
dot road sides in some big urban centers selling largely introduced ornamental
plants.
In addressing the importance of in situ germplasm conservation above,
we have pointed at the limitation of ex situ conservation. This has
been done without prejudice to the major promises which inhere in ex situ conservation
(van Soest 1990; Heywood, 1990; DaSilva et al., Ng 1991).
Comparatively, ex situ conservation in field gene banks, botanical gardens
and home gardens is not as capital or technology-intensive as other categories
of ex situ conservation. Consequently ex situ (field) gene banks
can be established or promoted with modest resources and public/community mobilization
and participation. But it is equally important to build capacity for conventional
seed bank and in vitro conservation in educational institutions and
research centres. The area of microbial collections and the biotechnology relating
to them also hold particular promise and they are also relatively inexpensive
to husband. Capacity building in this area should be pursued.
Introductions, afforestation and conservation
Introductions and afforestation
are veritable paradoxes in the business of conservation for two very important
reasons. Introduction and afforestation programmes (whether of indigenous
or introduced species) have the essential characteristics of monocultures
or oligocultures with the attendant consequences of simplification of ecosystems,
particularly instability. Secondly the experiences of introduction as exemplified
by the story of Endothea parasitica (the Asiatic chestnut blight)
on American Chestnut Castaenea dentata is a well-ingrained one (Elton,
1958) in the consciousness of students of the ecology of plant introductions.
One is not sure whether the environmental impact on genetic resources of native
plants have been assessed in afforestation programmes that centre on introduced
species such as Pinus, Gmelina, Tectona, Eucalyptus etc. or even on
indigenous species such as Triplochyton scleroxylon K. Schum., Terminalia L. spp
and Milicia excelsa (Welw.) C.C.Berg. While a lot of work is known on
provenance trials, selection, improvement and diseases and pests of forest
trees (Howland and Bowen, 1977; Ladipo, 1986), quite a lot of attention was
paid to straight commercial viability and productivity of silvicultural enterprises
(Ward, 1973; Oseni and Abayomi, 1973). The business of silvicultural plantations
involving single species or a few species need to be appraised from the point
of view of their potential for genetic erosion in natural habitats.
Conclusion
Various questions on the issues
of theoretical foundations, policy conceptions and strategies and priorities
on the conservation of genetic resources remain unsettled. The temptations
are always there to simplify the questions, particularly when quick answers
are demanded by policy makers and funding agencies (particularly those that
undertake commercial investments). The task however is to balance this need
for simplification of the problems with the need to provide a robust, long-term
and environmentally-sound basis for the conservation of plant genetic resources.
It is also important that we emphasise the need for the acquisition of the knowledge
and the skills of plant taxonomy, ecology and conservation beyond the immediate
needs of utilitarianism. This is a condition for building the demands of the
unseen future into the urgency of today's needs.
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