Plant Genetic Resources: Some New Directions

ADVANCES IN AGRONOMY, VOL. 45

PLANT GENETIC RESOURCES: SOME NEW DIRECTIONS J. T. Williams International Fund for Agricultural Research (IFAR) Arlington, Virginia 22209'

I. Introduction 11. Development of Global Activities A. The Framework for Global Activities B. Availability of Material C. Security of Materials D. Progress on Collection and Conservation of Crop Gene Pools 111. Areas of Research Which Impact Plant Genetic Resources Work A. Increasing Production B. Wild Species C. Stabilizing Production D. Agroforestry IV. Sustainability A. General Issues B Plant Genetic Resources Research for Biodiversity Conservation V. Current New Directions in Germplasm Management and Research A. Cooperative Networking B. Management of Collections C. Safety of Collections D. Links to Applied Research VI. Concluding Remarks References

I. INTRODUCTION Activities on plant genetic resources have accelerated greatly in the past two decades. Many of the constraints associated with sampling gene pools and conserving and documenting materials have been removed in the case of crop and forage species; programs have been initiated in scores of institutions and countries. The time has come to review the progress made and assess how the systems serve agronomists and plant breeders, and to look further at new directions that the scientific community needs to follow to ensure susI

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tained synergies between conservation and utilization. Such a review is timely because of a number of international developments: 1 . There is a widespread concern about the preservation of biological diversity, both genetic and ecological; there are overlapping needs for germplasm conservation and use for crop and forestry development and also ecosystem preservation. 2. There are major human population increases predicted especially in those areas where habitat protection is most needed and where land degradation and forest clearing continue. 3. There are major challenges in introducing sustainable agricultural systems that do not force a trade-off between current and future production but which meet expanding production needs. 4. Sustainable use of the environment, in both fragile areas and those of intensive agriculture, is essential, and agroforestry methods are now of great interest. 5 . The methodologies for using genetic resources to enhance crops have changed with the advent of new molecular techniques, and the types of materials useful in germplasm enhancement are now wider than envisaged in the past.

Recent years have highlighted the need to explore opportunities for integrated and well-managed farming systems that aim toward a decreased use of pesticides, fertilizers, and other chemicals. In this context it is expected that the sustainability aspects of emerging agricultural production systems include provisions for conserving biological diversity in the planning of development. Because of these concerns, those involved with the collection, conservation, and use of plant germplasm need to review how their current programs will meet actual needs in the immediate future. Perhaps the scientific community, in instituting its plant genetic resources programs, and expanding them over the past 2-3 decades has not always been aware that this time period has witnessed more adverse use of the environment and larger human population growths than have ever been witnessed in an equal period of time on this planet.

II. DEVELOPMENT OF GLOBAL ACTIVITIES A brief history of the development of global activities is necessary in order to appreciate the new directions needed in plant genetic resources work. The current activities grew from small beginnings in the 1960s. Crop scientists were aware that loss of diversity was inevitable as a result of

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agricultural development. This loss of diversity, or genetic erosion of the crop gene pools, was largely the loss of primitive populations, or land races, which had evolved over long periods of time under conditions of peasant agriculture. Certain regions of the world showed rich diversity for particular crops and traditionally plant breeders had been able to obtain materials from these regions for testing and use in crossing. The knowledge that this would become increasingly difficult led to proposals to collect and conserve samples of important staple crops, especially since the revolution stemming from the ever wider adoption of new high-yielding varieties of wheat and rice. At that time we saw the foundations laid for the establishment of international agricultural research centers (IARCs) which, in 1971, were to be associated into the Consultative Group on International Agriculture Research (CGIAR). In relation to crop genetic resources, the Food and Agriculture Organization (FAO) took a lead role in pointing to the needs and identifying priorities for collection and conservation; collaboration with the International Biological Program of the International Council of Scientific Unions strengthened this. Two parallel efforts made the voices of scientists more creditable; one was the establishment by the Rockefeller Foundation of committees to assess how complete were existing germplasm collections of major staple food crops (such as rice, wheat, maize, and sorghum), and to create field collecting teams to fill major gaps. These collections became integral parts of collections of existing, and still to be founded, IARCs. The second effort was a 1972 report of the U.S. National Research Council on genetic vulnerability, which addressed the need to meet future challenges to the adequacy of crop germplasm collections; this effort stemmed from implications of the southern corn blight epidemic. These and other efforts led to the creation of the International Board for Plant Genetic Resources (IBPGR) in 1974 as a center of the CGIAR, with a special relationship with F A 0 in Rome, Italy. The voices of crop scientists were echoed by the voices of those dealing with forestry, and again F A 0 took the lead. Whereas initially interest was aroused in collecting and conserving gene pools of widely used tree species, this interest is now concerned with genetic resources a p e c t s of arid and semiarid zone forestry and desertification control, agro-silvo-pastoral development, integrated watershed management and protection of the resource base leading to a major initiative such as the F A 0 Tropical Forestry Action Plan, and the call for action of a task force convened by the World Resources Institute, The World Bank, and UNDP in 1985. A number of these activities were foreshadowed by the consolidation in 1981 of a world conservation strategy through international conservation orga-

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nizations. The strategy influenced the larger conservation movement to think about plant genetic resources as integral to their activities. Up to now these diverse activities have developed with varying degrees of collaboration, often with recognition of common interests but, in practice, rarely with integrated scientific activities. Additionally there are now intergovernmental activities with the F A 0 promulgating an international undertaking and organizing a commission to oversee the implementation of the undertaking. The terms of reference of these F A 0 endeavors cover the wide range of plant genetic resources activities from work on crop gene pools to nature conservation. FOR GLOBAL ACTIVITIES A. THEFRAMEWORK

The programs that currently serve the needs of plant breeders and agronomists have grown out of programs that addressed specific needs. There were prototype genetic resources programs, which became greatly strengthened in countries such as the United States, the Soviet Union, Japan, the German Democratic Republic, and India; new genetic resources programs such as those of IRRI (rice), CIP (International Potato Center; potato), CIMMYT (wheat and maize), and later those of ICRISAT, ICARDA, IITA, CIAT, and ILCA for a range of crops and forages; and programs initiated de n o w largely through the stimulation of IBPGR. In the 1970s and 1980s there was the need to “build up” the collections and IBPGR put major emphasis on supporting widespread collecting of germplasm, due to the threat of genetic erosion, and early emphasis was on land races and primitive varieties. This emphasis was paralleled by stimulating the establishment, or scientific upgrading, of conservation facilities so that the materials could be stored and subsequently described. Numerous national programs became established. In the early years of IBPGR a number of attempts to organize regional programs faltered and the operational unit emerged as the national program. The global system that rapidly emerged resulted in the current wide array of national programs, some weak, some strong, and also the programs of the IARCs, all loosely federated according to mutual interest. The past few years have pointed to the real operational units being networked into an arrangement of institutions and scientists dealing with the germplasm of a particular crop rather than networks of national gene banks. It is now possible to envisage national collections as components of dispersed world collections of genetic resources of a range of crops. IBPGR is currently testing the feasibility of establishing such multidimensional networks by identifying participants and helping them to work

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together to determine the uniqueness of samples, the degrees of redundancy in collections, duplications for safety, and other joint activities. Ironically this approach would have been a logical follow-up from the early efforts of the Rockefeller Foundation mentioned above, but because in the 1970s and 1980s the global program was being built up with development assistance funding, a technical assistance approach was needed and asked for.

B. AVAILABILITY OF MATERIAL It has been a cardinal principle that crop genetic resources should be freely available to all users-breeders and scientists-and it has been widely observed in the past. Some governments have adopted policies of restricting the availability of genetic resources but these restrictions are largely related to industrial crops such as coffee, pepper, and others. A number of these examples-which do not accord with the international consensus-emerged in a period when great attention was being paid to mobilizing technology for world development. Political and economic considerations of the consequences of technological dependence in the least developed countries were pointing to the need to discover mutualities, to rectify the unease felt as a result of previous often shortsighted actions, and to find new possibilities and practices in the so-called NorthSouth relationships. It is not surprising that unease at the only existing global “system,” that of IBPGR, to make material available as an act of voluntary collaboration was expressed in the early debates leading to the international undertaking of FAO. There is no conflict because the whole international community wishes to see enhanced freedom in the availability of materials, but the discussions are useful to identify the constraints on programs in poor countries. Constraints and availability are interrelated and because availability relates to good management of collections (Chang et al., 1989). Additionally, there have been a number of misunderstandings on the “values” of germplasm and potential recompense mechanisms, which form a continuing dialogue, often to the bewilderment of the scientists involved in the practical work on genetic resources. C. SECURITY OF MATERIALS Seed materials are dried and stored at low temperatures for conservation. Such conditions obviate the need for frequent grow-outs to regenerate stocks. The more stringent storage conditions (base collections)

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ensure longer periods between regeneration and provide a degree of security. In order to avoid any disasters, duplicates are held elsewhere in other base collections. IBPGR built up a group of centers in all parts of the world which agreed to hold the germplasm of particular crops in base collections. Seeds, when they can be stored, are convenient units to handle because they have the full set of genetic information in the embryo, and most seeds are relatively small. Seed physiology research has provided scientific guidelines on the preparation and storage of seeds to assure long-term viability. Research in progress is aimed generally at more cost-effective storage, for example, the use of ultra-low seed moisture content as a substitute for low temperatures or the use of natural environmental conditions that save energy costs. Most of the major crops can be stored ex situ as seed in gene banks; however, some cannot. These are either clones that cannot be reproduced from seeds, certain trees with large seeds that have high moisture contents, or some crops that are sexually sterile. These types of materials are conserved as vegetative material (plants) in field gene banks but their security is not assured until better methods can be organized to maintain them as small pieces of tissue in culture. D. PROGRESS ON COLLECTION A N D CONSERVATION OF CROPGENEPOOLS

The major efforts on collecting germplasm, the priorities accorded over the past 15 years, and the development of facilities to conserve the collected materials have been described in the annual reports of IBPGR, in Williams (1985), and in Plucknett et al. (1987). These will not be reviewed here as the purpose of this paper is to highlight new directions in the shortto medium-term future.

Ill. AREAS OF RESEARCH WHICH IMPACT PLANT GENETIC RESOURCES WORK A. INCREASINGPRODUCTION

The success of crop production depends on the availability of appropriate germplasm and the sources of the samples of germplasm. In addition, the manipulation of the germplasm has changed markedly in the past 100 years (Duvick and Brown, 1989). Manipulation of germplasm through

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plant breeding, and use of the appropriate agronomic practices (tillage, monocultures, fertilizers, etc.) are the basis of modern agriculture. The germplasm used routinely is largely highly selected; this is essential as new cultivars rapidly replace each other. Breeders tend to use elite materials, rather than primitive, relatively unselected forms such as land races, because of the undesirable linkages in the latter. Whereas the land race material is adapted to the site of origin, it is rarely adapted for the new breeding aims, and additional generations of selection are not wanted by the breeders. Despite these generalities, crop breeding strategies continually require diverse sources of germplasm, often materials of the specific crop from widely separated geographical areas. Vavilov, the founder of the U.S.S.R. genetic resources work, exploited this principle. It was also an important aspect of the green revolution in cereals, for example, the dwarf wheats bred from hybrids between East Asian and U.S. cultivars (and the form used from Japan had in its lineage earlier U.S. cultivars). There are two aspects to continuing production; first, efforts to maintain stable production. and second, those to improve yield. The germplasm collectors and the curators of genetic resources collections bear heavy responsibilities because their decisions result in what is actually available for breeders, even in the future. The presence or absence of an allele can only rarely be supposed when plants are looked at in the field. Also, variation seen by the eye may be environmentally determined. Hence “looking for useful genes” is not tenable. Since breeders need specific alleles to transfer in their crossing program, should the strategy for collecting be to collect alleles (seen as a specific character or unseen, e.g., a resistance gene), or to collect genotypes? The widely accepted practice is to collect populations of genotypes because, in effect, breeders require certain alleles in plants that will be used as parents with general adaptation to the environments to which the progeny are aimed. The pragmatic decision is that germplasm available to breeders should represent an assemblage of populations from the range of geographies and ecologies of the crop gene pool without bias as to the presence or absence of rare alleles. In this way the required alleles will be present in the spectrum of genetic resources samples. Except for a few major crops, such as rice, this strategy has rarely been implemented since collections have been built up from amalgamation of old breeding samples along with certain recently or newly collected samples. As a result, the collectors and the curators have an urgent need to “sort out” the materials and document them properly, for example, by aggressively seeking missing collecting site data still in notebooks and by planning targeted new collecting. In this way the samples will be more accessible to breeders in their efforts toward continuing production.

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The current situation for many crops is that genetic resources exist and are available but are not yet known well enough for widespread use despite, for major crops, the existence of relatively large collections of land races. In practice, a great deal of diversity has been amassed for conservation by the salvaging of land races, work spearheaded by IBPGR in 1978-1988. This leads to the question: what more needs to be collected? Numbers of accessions in lists are an inadequate guide. Furthermore, there will always be needs and opportunities for supplementing the collection. Additionally, the emphasis has moved markedly towards incorporating samples from the wider gene pools, rather than solely from the cultivated ones.

B. WILD SPECIES Recent decades have seen interest in wild species related to cultivated plants as research has been carried out to elucidate evolutionary relationships and to understand how closely the species within gene pools are related and which species are the progenitors. Cultivated plants are relatively recent in time and the course of evolution of the wild species probably spanned millions of years during which gene mutations accumulated. In the field, some related wild species hybridize with domesticates when distributions overlap and introgression goes in both directions; weed races often occur, and Harlan (1975) saw this genetic enriching as a causal effect in creating microcenters of diversity. Due to the environmental changes that have occurred in relation to agriculture, of course, the currently seen ecologies of some related wild species may not be the same as when domestication took place. Nonetheless, the ecological amplitude of wild relatives may far exceed those of the crops developed from them. Hybridization between wild species and domesticates, especially in the 1970s, showed the potential of wild germplasm. For instance, expressions of heterosis or transgressive segregations for yield occurred in many crops: pearl millet, sorghum, barley, rice, wheat, maize, egg plant, sweet potato, oat, potato, groundnut, tobacco, and sugar cane. Maybe most interest stemmed from wild relatives proving to be sources of resistances to diseases and pests, but other attributes related to quality were also obvious in some cases. Use of wild species in breeding was largely limited by the ease of crossability but interest was apparent in the scientific community because of the widespread trend to narrow the genetic base of cultivars. Where the base was considered to be too narrow, breeders introduced germplasm from exotic cultivars when new sources of resistance were needed as in the case of soybean breeding in the United States. Duvick and Brown (1989)

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used this example to illustrate that backcrossing to eliminate as many as possible of the other exotic genes became supplemented with screening exotic cultivars for useful agronomic traits, and deliberate attempts were made to introduce maximum amounts of exotic germplasm into the elite background, thereby providing desirable agronomic backgrounds to new breeding stocks. Breeding materials are now far removed from the few original accessions which had been used as the basis for U.S. cultivars. Concern in the 1970s at narrowing the genetic base of crops, with possible problems of vulnerability, have indeed led to narrowing and broadening cycles in a number of crops. However, as mentioned in the case of soybean, o r for sorghum, wild species were not needed for these efforts. Although wild species are vital resources for breeders, they are usually used as a last resort and depend on the breeding history of the crop; they are rarely used in breeding barley, wheat, and maize but more frequently in potato, sunflower, and peanut. Two factors have caused advances in the use of wild species in breeding. The first has been the recognition, especially in the 1980s, of widespread environmental problems, loss of fragile ecosystems, and over-exploitation of natural areas, many of these the homes of the wild species. The second has been advances in biotechnology, which have made wide crossing easier and which provide new opportunities for crossing between more remotely related species. Breeders will never use wild species if they can find the genetic diversity they need in the cultivated germplasm. Hence the plant genetic resources community had to accelerate collection and conservation because of the threats to species’ gene pools and because rapidly developing genetic engineering was bringing these species quickly to the stage where a whole new resource will be available for exploitation. IBPGR accorded high priority to this work (Williams, 1985); long-standing work on building up collections of wild species of rice and potato at IRRI and CIP were supplemented by new or newer programs on peanut (IBPGR, U.S. and ICRISAT), sweet potato (IBPGR and CIP). pearl millet (IBPGRand ICRISAT), and Triticeae grasses (Chapman, 1989). In parallel with these shifts in emphasis the scientific community had witnessed a wide exploitation of biochemical methods. lsozyme research became commonplace in the early 1980s as tools for plant breeders, population geneticists, cytogeneticists, and others. Although many of the isozyme systems with the most promise had been known since the term isozyme had been coined (Markert and Moller, 1959), their application to help design experiments to introduce alien chromosome additions with markers was more recent. Whereas wide hybridization was used largely to generate new allopoly-

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ploids (e.g., Triticale) and as a mechanism to introgress genes from wild species into cultivated stocks, in uitro techniques became available to overcome barriers seen in attempts to obtain interspecific or intergeneric hybrids. They do not replace the value of allopolyploidy, which will remain a tool in reconstructing old crops or creating new ones or broadening genetic bases. Allopolyploids have the possibilities of new character combinations, increased vegetative vigor, and permanent hybridity (Simmonds, 1979). When wild relatives differ in ploidy level from the crop species creation of allopolyploids is a useful step in transferring desirable genes. Additionally, the use of highly heterozygous autopolyploids as parents for allopolyploids can generate variability. Although chromosome doubling cannot be used to produce these parents, protoplast fusion to produce somatic hybrids is one method. The in uitro techniques now used to overcome problems are: 1. Embryo culture. Immature embryos that abort can be rescued and transferred to in uitro culture, thereby permitting development that would not otherwise occur and producing a plant that is an interspecific hybrid. In some cases hybrid ovules-or whole ovaries-can also be cultured; 2. In uitrofertilization. Methods have been developed to culture ovules and pollinate them aseptically using diverse parents. A low number of these can sometimes produce plants; and 3. Somatic hybridization. Although not as widely used as originally envisaged, naked protoplasts have been fused, induced to divide, and plants regenerated, the latter being often the most difficult (Jensen, 1981).

Additionally, in uitro methods are used to aid pairing of chromosomes in alien crosses. This is done by generating substitution or addition lines by preferential elimination of most of the chromosomes of one genome. Culture may also increase genetic recombination between two genomes used in wide crossing (Orton and Steidl, 1980; Larkin and Scowcroft, 1981). Such experimentation also led to clearer recognition that plants regenerated from cell and tissue culture often exhibit variability not seen in the parental material (“somoclonal variation”) and that this can be used in breeding (Scowcroft, 1985). Options in breeding using somoclones were taken up by potato breeding programs, for example, in the United States, the United Kingdom, and the Federal Republic of Germany. A wide range of other programs can be found in the literature but problem-solving ideas are perhaps the most exciting, such as the development of resistance to black Sigatoka disease in Musa [Fischer, in International Institute of Tropical Agriculture (IITA), 19881. The literature is now so wide on the combined use of in uitro techniques,

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isozyme techniques. and breeding that wide crossing, and hence a much heightened interest in wild species as genetic resources, is firmly established, vindicating in part the pleas of a number of early founders of the genetic resources movement to pay more attention to wild species. It is not the purpose of this review to summarize all these scientific developments which, through user-driven demands, have caused a coalescing of interdisciplinary sciences, but rather to pose a number of questions that have not clearly been resolved and that will inevitably prompt new directions in scientific work in the immediate future. To further develop current systems so that specific areas of research can be addressed in a meaningful way, various constraints must be surmounted. These constraints are discussed next. In the first instance it is extremely difficult for any one institution to maintain a world collection. When IRRI was planning its strategy for the wild rice species it became apparent that location of their research in Los Baiios was not the most conducive to growing and regenerating all the wild species. Similarly, when a world collection-invaluable for research, prebreeding, and breeding-is established, it relates to the interests of the scientists and the institution where it is developed. A case in point is a world collection of wild material of Hordeum sensu lato at the Swedish Agricultural University. Materials from China, Peru, Mexico, California and Arizona, U.S.A., and scores of sites in the Mediterranean, Southwest Asia, and elsewhere represent very diverse ecologies posing major constraints on growing-out of samples and on maintaining populations as accessions in a genetic resources program. Nor would constraints, in any way, be removed if the collection was handed over to an IARC with responsibility for breeding barley, in this case ICARDA in Syria. Other collections of wild species exhibit similar constraints, whether they be several collections of wild potato species (variously at CIP, Peru; Sturgeon Bay, U.S.A.; Dutch-German Potato Genebank at FAL, Braunschweig, Federal Republic of Germany; Commonwealth Potato Collection, Scotland, U.K., or the collection at VIR, Leningrad, U.S.S.R.), groundnut (ICRISAT, India; or Texas, U.S.A.), or wheat (VIR, U.S.S.R.; Kyoto/National Seed Storage Laboratory, Japan; ICARDA, and others). IBPGR has clearly stated that most of these species are best left in the wild unless they are under threat. This is logical but conflicts with ( 1 ) the emerging needs for readily available samples for use, and (2) the needs to develop strategies on how wide specific gene pools need to be for future utilization with the rapid advances in biotechnology . It is my opinion that the full range of constraints to effective genetic conservation of wild species gene pools will not be removed by merging these special collections with those of cultivars. There are several convincing arguments for this opinion. First, most collections of cultivars are

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held in gene banks associated only with expertise in agronomy and traditional breeding; few such gene banks have access to facilities for embryo rescue nor staff well qualified in seed physiology and handling of wild species. Additionally, a range of accessions representing populations must be maintained and there is a tendency for collections to be species collections of a botanic garden type rather than a collection of wide gene pool diversity. Much more emphasis needs to be placed on developing a strategy for the collection and on how to build it up (e.g., for wheat, see Chapman, 1985). The newer concept of IBPGR to network collections will not remove the constraints on maintaining wild species collections, because they are best left in the hands of competent scientists with subsets kept along with the cultivated materials. Each crop will need to be sorted out on a case-bycase basis, and I expect that the special purpose collections need to go on being maintained in a diversity of institutions, whether they be specialist gene banks or university research departments. I have attempted to get IBPGR involved in devising a strategy for this and seeing that funding for genetic resources work-largely at present from development assistance funds-takes into account these other requirements. Additionally, with the world’s botanic gardens becoming organized through IUCN (International Union for the Conservation of Nature; Bramwell et al., 1987) and becoming educated slowly away from specimen collections to those of genetic diversity (Williams and Creech, 19871, the synergies are apparent and provide a clear base for strategic planning. Additional scientific interests in in situ conservation of crop relatives (e.g., barley in Israel) which can be sustained into the future will have to be built into the strategies, but by far the greatest synergy will be between preservation of populations of perennial species in in situ reserve areas and the germplasm in ex situ collections. There are great opportunities here, but to date little progress because, I suspect, getting the institutions with vested interests together is not the prime catalyst, due to funding situations; rather, the catalyst is the commissioning of scientific, institutionneutral strategic planning on their behalf. These questions are complex because the range of vested interests extends more widely than, on one hand, plant genetic resources interests, and on the other hand, interests in ecosystem preservation. Until recently, it was possible to address these in a mutual way (Frankel and Soule, 1981; Williams, 1982; Ingram and Williams, 1984);however, the whole question of biodiversity has assumed major significance and so too has sustainable use of the environment, particularly in relation to peasant populations in threatened areas. There is a tendency for compartmentalization of interests at the funding level, an explosion of interests in the areas of overlap-

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ping science, and we need a much clearer set of well-defined cooperative activities based on a diversity of institutional relationships. For instance, the People’s Republic of China assigns responsibility for cultivated germplasm to the Academy of Agricultural Sciences and for wild related germplasm to the network of botanic gardens; contrast this to the National Plant Germplasm System of the United States where they are integrated, or to IARCs where they may be integrated, or where wild species are covered by networking with other institutions. This makes strategic planning all the more essential in order to put in place the mechanisms needed now, not 5 or 10 years down the road. In some cases the wild species collections already serve a range of crop users. The wild grasses of Triticeae, to be found over a large portion of the earth’s surface, are of current interest to breeders of barley, wheat, rye, and to forage breeders. Currently collections exist for scientific research or for breeding of a specific crop; few are represented by high-quality seed accessions in long-term storage, and cooperation is almost wholly on an ad hoc basis. It should also be remembered that many crops not far removed from wild species genetically are those of major interest in sustainable development in the rural conditions in the tropics and subtropics. Many of these are perennials for which no adequate germplasm collections exist. For any enhancement, ex situ collections are essential and this area has been totally neglected up to the present. The problem has received minimal recognition by any international organization, and funding is virtually nonexistent since these materials hitherto have been outside the interest of food crop or forage development. Conservation of this type of material has to be put in place in relation to productive use; if not, it remains an imperative for ecosystem preservation. Whereas cost efficiency is now ranking high in terms of ex situ conservation of staple food crops, little attention and virtually no strategic research has been carried out on perennial materials in the tropics. A recent paper on management and use of collections stated: “The costly investment in plant germplasm collections must be justified by profitable returns through use and further enhancement,” and further, “The wild species generally remain the least conserved and little exploited category, although impressive advances in breeding have been attained in several crops such as wheat, rice, tomato, sugarcane and tobacco, with genes contributed by the wild taxa” (Chang, et al., 1989). In relation to a whole series of crops, these sentiments, based on work with major crops, will require reinvestigation. Lastly, as mentioned earlier in this section, the collection of wild species has shown significant advances. In the early 1980s “best-guess” as-

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sessments of the state of collections of wild relatives were made for the major food crops and progress since then has not yet been synthesized into a review. IBPGR might find this a useful exercise to promote support; it is unlikely that it can await new networking proposals with the subsequent time-consuming sorting out of collections. It is also becoming increasingly obvious that “yellow pages” in the form of directories of germplasm collections, so urgently needed over the past 10 years, no longer fulfill the information needs of enquirers. This was the opinion expressed by scientists at a meeting of the Institut de la Vie, in Washington, D.C. in May, 1990, which proposed a new program to address new and already apparent information needs. C. STABILIZING PRODUCTION In recent years attention has been paid to the phenomenon of variability in yield, and the question has been asked whether new production technologies and modern cultivars are inherently more variable. There is general agreement that yield variation can be greater when high-yielding modern cultivars are used, and that average yields continue to increase due to wider use of such cultivars along with the modern inputs that such cultivars are able to exploit. An important workshop on this question was held under the sponsorship of JFPRI and the German Stiftung fur Internationale Entwicklung/Zentralinstitut fur Ernahrung und Landwirtschaft (Hazell, 1986). Is there a correlation between variability of yields in modern agriculture and the narrowing of the genetic base related to the development of the successful cultivars; and what attention do breeders give to the development of cultivars with high and consistent performance? Holden (1986) points out that breeders achieve this latter goal by ( I ) purposive breeding from parents selected for their ability to give stable progeny, and (2) selection among advanced lines of progenies not specifically bred for stability, and through multisite trials to select those with more stable yields. Nonetheless, the priority given to yield stability in breeding programs will depend on the agricultural system where the cultivars will be grown. If, for instance, the farmer can control the systems by irrigation and chemicals, selecting for genetic stability may be less important than emphasizing yield. In many developing countries, local organizations still need to learn how to manage the newer high-yield cultivars. Agronomy becomes the overriding question, rather than extensive manipulation of the genetics of the cultivars. There is no evidence that the variability results from the narrowing of the genetic base; attempts to experiment with mixtures of pure lines, thus providing a degree of buffering due to heterogeneity, have not led to major

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advantages since management is difficult. Comments have often been made that the old land races, as mixtures of genotypes, provided a degree of stability, but comparisons with modem cultivars are spurious in that the latter are successful in producing high yields and have made adaptations and good resistance to environmental stresses. Duvick and Brown (1989) have eloquently pointed out that today’s practice of using genetic diversity in time-by genotype replacement over time-is more or less equivalent to the primitive practice of using genetic diversity in place-by hetrogeneous land races. They stress that even in primitive agriculture, diversity in time also occurred but at a slower rate. Modern breeding exploits in a purposive way sources of diversity and wide ranging germplasm exchange, phenomena of modern agriculture. A clear understanding of this somewhat negates well-intentioned efforts to conserve old land races on farms under conditions of primitive agriculture. Breeding for stability is therefore largely part and parcel of breeding for increased yield. It requires readily available germplasm from a wide range of sources, which has to be conserved and characterized and will rarely rely on locally conserved stocks, whether in a gene bank, or on a farm, or in some type of reserve. Genetically diverse parents from diverse areas will remain the key, and products of breeding have to be coupled with specific agronomic practices whether high- or low-input. Breeding programs for most crops have also shown that breeding for stresses such as drought requires screening of a wide gene pool rather than simply the pool of advanced material; the same occurs for disease resistances. Hence genetic resources will continue to be essential on a continuing basis.

D. AGROFORESTRY 1 . Past and Current Directions The development of farming systems that are sustained over time has constantly changed since the dawn of civilization, and historical changes have related to changing pressures on resources. The widespread alarm over environmental changes in recent decades also relate to changes in areas of productive capacity. According to FAO, 16.5% of the rainfed cropland in Africa will be lost by the year 2000 without renewed and improved management efforts; UNEP estimates that at least 80% of the croplands of the and to subhumid zones in Africa have lost a significant portion of their productive capacity. Clearly, these examples point to the need for new strategies because unscientific land-use practices on marginal soils rapidly cause soil erosion. Agroforestry provides one answer to a number of problems. It involves the integrated cultivation of woody species, mostly perennials, with crops

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and animals, so that in a symbiotic way, ecological interactions between woody and nonwoody plants sustain and diversify total output. Some agroforestry systems are ancient. Shifting cultivation where trees and crops alternate in time and space has continued in some areas (e.g., Amazonia) for millennia. However, due to population pressures, most of these systems are now out of balance, promote soil degradation, and lead to land degradation. For more than 15 years major international efforts have highlighted the need for modem agroforestry systems that combine food production with environmental protection. The International Council for Research in Agroforestry (ICRAF) was established in 1977 following a study initiated in 1975 by IDRC to address problems of tropical forestry. ICRAF began examining the technological and socioeconomic constraints limiting the spread of agroforestry practices, and other studies (e.g., a study of the Board on Science and Technology for International Development) stressed the urgent need for work on shrubs and trees for fuelwood production. It was widely appreciated that the demand for woody plants for various uses could not be met by the existing supplies of appropriate germplasm. Despite a plethora of terms-village forestry, agroforestry, community forestry, social forestry, agrisilviculture, and others-it took some time for scientists to distinguish between trees for forestry and trees for agroforestry. Until then there was no need to distinguish between them but that rapidly changed with the emergence of the concept of multipurpose trees. Information on plant materials that could be used in agroforestry systems was scattered, hence it was necessary to collate information available in the literature on species suitable for agroforestry. There are two problems: first, there is no distinct group of species; and second, most woody crops for use in agroforestry situations had been developed to suit monocropping. Essentially a starting point is indigenous knowledge since peasant farmers have adapted tree species to their particular agricultural and dietary needs. Often the peasant systems were low-input and agroforestry was always seen as integrated land use especially suited for marginal areas and low-input systems. ICRAF carried out a survey in 1978 that showed that some forms of agroforestry occur in almost all developing countries of the world, for example, the tanungya system, which spread widely from Burma for hill cultivation where the initial stages of forest plantations include agricultural crops. Research needs were many and ranged from identifying suitable forest species that permit an understudy crop to testing the shade tolerance of various agricultural crops. Emphasis on the research that resulted was heavily geared to the location-specific nature. Nonetheless, a number of generalizations were possible. First, agroforestry systems are essential for

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consideration in degraded situations or fragile environments and hence have major application in arid and semiarid zones, shifting cultivation areas, acid range areas of the tropics, and in areas of mountain agriculture. Second, the methods of admixture of species, although dependent on soils, climate, management, and other needs, can be grouped into broad categories: for example, intercropping (trees with agricultural field crops); planting shade-tolerant woody crops in strips in primary or secondary forests to provide a canopied mix of tree crops and forestry species; close planting as wood lots around habitation and as fences, windbreaks, etc. ;planting trees in a planned manner between areas of traditional agriculture; and specific methods to retain soil in hill areas or zonal strips in arid areas using shrubs for fodder and mulch. A number of publications gathered together data scattered in the literature, for example, on suitable agricultural species, both field crop and woody (Nair, 1980), on specific types of trees and shrubs for regions such as the Sahel, or for management of specific soils. The intensification of interest in understanding and designing agroforestry systems was spurred by two other factors. On one hand, a great deal of research had been done on multipurpose leguminous trees and shrubs and they were being widely used to address rural needs (e.g., Sesbania, see Brewbaker and Hutton, 1979; Leucaena, see Felker, 1979; Prosopis, see Saunders and Becker, 1989). On the other hand, attention was being paid to ecological development needs in the tropics with an aim to plan better for sustainable development through managing and conserving renewable resources (Lug0 et al., 1987) and data were beginning to flow from important development projects, especially in the tropics. What was the situation for plant genetic resources? With regard to agricultural field crops for use in agroforestry a great deal was known from agricultural research, although information on suitable genotypes of tropical tree crops has rarely been recorded. In some cases the information is rudimentary (e.g., “vanilla grows best under trees”), but there is no information other than on a limited number of varieties that form the basis of vanilla cultivation. Nothing is known about the potential of primitively cultivated forms in Central America; essentially successful incorporation into agroforestry schemes will be measured by how far the optimal growth requirements will be satisfied and by what effect the modified (i.e., agroforestry) environment will have on the growth and productivity of the species (Nair, 1980). A number of less familiar perennial food crops-breadfruit, peach palm, numerous oil-producing palm species, caryocar, jojoba, cow tree, perennial pigeonpea, mesquite, and others-are noted as having considerable

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potential for contributing to the more usual production from annual staple crops in intercropping situations (Rachie, 1983) but it was recognized that research is essential, including plant exploration, for the perennial species, their selection for complementarity with other crops, and specific genetic improvement under appropriate management techniques. Rachie stressed the real need for plant exploration for economically useful new perennials and tree crops. Research should stress those with established potential, which could then be more extensively collected, and genetic improvement and agronomy could be studied. Although we have seen over the past decade a certain amount of interest in some of these species, and although collecting has occurred (e.g., peach palm, Clement and Arkcoll, 1989; other native neotropical palms, Balick, 1989; and breadfruit, IBPGR, 1988), much more remains to be done before specific genotypes can be selected for specific agroforestry systems. For example, projects tend to use “likely” sources that may or may not be successful. In a trial in the upper Ecuadorian Amazon survival of fruit trees grown in combination in pastures showed Annona, avocado, breadfruit, guaba (Inga edulis), and guava (Prentice, 1979) giving vigorous growth on good sites and only guava on poor sites. There are weedy local forms that could be selected for poor sites but such gemplasm was not available for use. Long-standing research and development using nitrogen-fixing trees and others popularly grown (e.g., eucalypts and shrubs) have provided data and new plant management patterns, such as provision of fuelwood and/or wood under regimes such as pollarding or coppicing, either alone in woodlots or in agroforestry situations. An important stage in considering genetic resources was a workshop held by ICRAF, IBPGR, and CFI (and sponsored by ICRAF, IBPGR, and GTZ, Germany) in 1983 to discuss multipurpose tree germplasm (Burley and von Carlowitz, 1984). This examined existing priorities provided by F A 0 (largely from recommendations of a panel of experts on forest gene resources, IUFRO, CFI, CSIRO, NAS, NFTA, and others) and pointed out that it is clearly desirable to establish coordinated and compatible systems of data handling and to make these available. There is a need to short-list candidate multipurpose trees and shrubs, and ICRAF has built up a database of over 1,000 species which can be used for preselection, based on computerized matching of sites, uses, and tree characteristics and which focuses on species most likely to succeed in a given environment, technology, and land-use system (von Carlowitz, 1989). However, germplasm collections to supply a wide diversity of these candidate woody species hardly exist.

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2 . New Directions f o r Plant Resources Used in Agroforestry Although the 1983 workshop referred to above initiated a discussion on genetic resources collection, conservation, documentation, and use, it considered that prioritization was not easy since it needs to be considered at various levels: local, regional, and global. Existing lists, for example, those of F A 0 for fuelwood, multipurpose lists of IUFRO, master lists of nitrogen-fixing trees of NFTA, or those for specific purposes, such as savanna trees for Africa or fodder species for hill regions, should be considered only as illustrative examples. This approach has, however, led to little new action on collection, conservation, and documentation other than expansion of existing programs, often established with different aims. We are currently in a situation where some new priorities will have to be decided and acted on quickly, especially where there are recognized threats of genetic erosion, since few accessions are in gene banks and the range of genetic diversity available from suppliers is narrow. There are eight areas where research is urgent: 1. Existing documentation on genetic resources of annual crops and forages which will be used in agroforestry systems requires the formulation of additional descriptors and descriptor states relevant to agroforestry practices. A number of these will relate to broader evaluation, especially those for assessing agronomic importance, and there will be a range of expression due to environment-genotype interaction. They should be limited to descriptors of fairly wide application and not be too site specific. Additionally, further passport descriptors might enhance predictability for agroforestry testing. There are many land races or primitive cultivars that were or will be collected from sites such as small holdings, where admixtures of cultivated field crops and trees or shrubs are the norm. Current descriptor schemes do not include these types of data. Many food crops that have not received a great deal of agronomic or breeding attention would fit such a category, especially crops such as roots and pulses, in the tropics, although there would be data available, if acquired, on others that have been used in major breeding programs. 2. Perennial woody crops pose many more problems. Some, such as those that have been used widely in plantations, already have databases on germplasm holdings or their databases are in the process of being developed. Cacao is now the subject for an international databasing exercise, and it would be logical to consider the relevant descriptors for agroforestry purposes since the largest part of the crop is still produced by small holders. Unfortunately, databasing of collections of most of the perennial tree crops is either nonexistent or rudimentary and a great deal of work is

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needed in most cases to refine preliminary lists of descriptors or to devise them de novo. 3. Underexploited perennial crops are likely to find an important niche in agroforestry systems. Many are extremely variable. Germplasm collections exist but are usually geared to other interests, and frequently are not available in sites and countries where they are likely to be needed. Moreover, there is no overall funding to rectify this in the near future. In a survey of over 30 tropical and subtropical fruits and nuts only just over half have significant germplasm holdings (IBPGR, 1986), but making materials easily and rapidly available for testing programs for agroforestry will require specific support. The position is likely to improve as the new IFAR Tropical Tree Crop Program becomes fully operational, but this will work on a crop-by-crop basis and a large level of funding and time will be needed particularly at the national level. Some national programs have built up special-purpose collections which will be of great interest in agroforestry. The All India Coordinated Research Project on Arid Zone Fruits (AICRP) is a case in point, which is involved with evaluating materials at 12 centers of the AICRP and at 25 other centers. Pateek (1988) vividly points to the international need to hold materials in agroclimatically suitable locations as a strategy for international conservation efforts on this type of material. 4. Wild tree species that are known to be of potential use, for whatever purpose, are unlikely to receive attention except at the local level and virtually nothing is known of their genetic variation. Although there are continuing ethnobotanic interests, such species are likely to remain orphaned by the research community at present unless sufficient scientific interest can be generated, as in the case of peach palm. 5. Since agroforestry incorporates livestock into the systems, it is urgent that the priorities available for browse woody species be reassessed. Those developed by IBPGR are probably too general for meaningful technology development. 6. Whereas success of the agroforestry systems depends on the selection of suitable woody species with characteristics such as quick establishment, fast growth, and acceptable ideotypes, research is certainly needed on “tailoring” tree species to agroforestry systems. The basis for this will be greater knowledge of the genetic variation and its distribution for specific characters in natural stands and exploitation through breeding. In most cases exploitation is limited to provenance testing and selection but for a number of species breeding will be required. Sufficient knowledge exists for priorities to be determined; if these were produced and collecting accelerated it would reduce the current “discrepancy between demand and supply of germplasm” (Shankarnarayan, 1988). 7. Trees are usually collected and put into provenance stands. For

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agroforestry there is probably a justification for setting up special-purpose working collections as field gene banks with back-up storage of seed, if this is possible, in appropriate facilities such as deep-freeze chests, and also linked to multiplication to provide planting materials. This could be incorporated into a national genetic resources program, but we have not evidenced much planning in this area. Such facilities would aid a whole series of development activities other than crop or tree breeding; for instance, the integration of projects dealing with sustainable development in buffer zones of nature reserve areas, planned Iand-use changes, and others. 8 . Agroforestry research has much to gain from synergies with ecological research especially when wild species are to be used. There is substantial literature on natural disturbance and patch dynamics on the responses of woody plants to disturbance, including plant evolution in disturbed environments (Pickett and White, 1985) but little evidence of interdisciplinary research involving agriculturists. Similarly, the genetics of colonization, where the literature is largely related to annual species or herbs, would benefit from joint research. Whereas agroforestry is at the stage of recognizing many systems for growing trees (in fields, or farm boundaries, woodlots, etc.), the tree species have not been researched. In many cases it is not known whether it is possible to select fast-growing, high-yielding native tree species. Tejwani (1988) makes a plea for prioritization and a networking approach to research based on experience in India where traditional agroforestry practices are common. The time has come to devise a number of themes of strategic research and to deemphasize the major emphasis on on-site trials. Genetic resources collections will be essential and plans have not yet been more than promulgated. Lastly, it will be essential that germplasm systems are integrated with those that exist or are developing in national programs and research institutions.

IV. SUSTAINABILITY A. GENERAL ISSUES International agricultural research, particularly through the CGIAR, has been evolving from initial aims of producing broadly adapted high-yielding cultivars toward producing more and more cultivars tolerant of stresses, which do not require the heavy chemical inputs and hence are bred for more efficient use of nutrients and do not overtax available soil and water

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resources. This statement was part of the concluding remarks of a CGIAR Committee on Sustainability, which presented a report in May, 1990. Additionally, the committee pointed out that farm management priorities along with appropriate policy and social settings require technical assistance and training and the interplay of numerous international and natural institutions, universities, and voluntary organizations. The emphasis on sustainability of agricultural production systems has implications somewhat different from the wider sustainable use of the environment, although the two are inextricably linked. In terms of the former the main issues relate to: 1. protecting the genetic base of agriculture; 2. preserving the natural resource base; 3. research in less favorable environments; and 4. concern to reduce external inputs.

In terms of the latter, the major issues relate to land use, ecosystems preservation, and economics and government policies. Plant genetic resources are the very basis that provides insurance for agriculture. However, one conceptual problem must become more widely appreciated outside the large research centers and especially at the level of developing country programs; that is, the difference in use of resources. In modern plant breeding the genetic resources are largely used as sources of genetic material, genes, and gene assemblies, which are drawn on for particular purposive aims. In most cases the reservoir-a plant with a particular genotype-is less important. Nonetheless, plant resources are still used for plant introduction, a widespread practice in horticulture and range science. Additionally, forestry, dealing mostly with wild species, is largely plant introduction. It would also be advantageous to enhance the domestication of medicinal plants and local crops that are gathered and also semidomesticated. Much interest in wider sustainability must relate to selection of ecotypes of these latter examples rather than the plant breeding practiced by crop scientists where specific genes for a particular character state are transferred into adapted genotypes. Much of the plant introduction successes relate to agronomic packages developed at the same time. It should not be forgotten that some plantation crops, domesticated in recent times, have owed most of their increased yields to agronomy rather than to breeding. There has been a widespread tendency for national genetic resources programs in developing countries to merge the two functions mentioned above, and while trying to emulate the spectacular breeding programs in other parts of the world and in international centers, they have often lost sight of the often obvious needs for aggressive plant introduction work

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along with agronomic trials. It should not be forgotten that most breeding programs for intensive pasture management developed from introduction programs, especially in the United Kingdom, Australia, and more recent work in CIAT and ILCA. These programs have had major impact on pasture improvement in many parts of the world. Frankel (1985) stressed the difference between plant and gene introduction in the context of the crop germplasm collections held in Southeast Asian countries. In the former case the aim of the collection is mainly ecological relevance and in the event that no breeding is currently practiced nor envisaged, then the collection should be based on ecologically different cultivars or ecotypes rather than as sources of genetic materials that might never be used. Those aspects of breeding that will be geared to sustainability issues will have implications on the genetic resources programs. Almost certainly it would be prudent to place more emphasis on knowing more about the genetic variation in the land races that are already in collections, and more interest in sorting out specific groups of accessions from particular ecologies and screening for specific traits. This type of work has been built into the evaluation program of, for instance, the rice collection in IRRI, but parallel types of work still need to be initiated for collections of a number of other crops. There are millions of rural poor in areas with fragile production systems in vast arid and semiarid zones and in areas bordering tropical forests. Due to population increases sustainability issues are a high priority on the agenda, and breeders and germplasm curators need continuing dialogues to develop strategies in relation to the materials with which they work. Foresight is necessary to shorten the time scale needed to provide the technologies. Since, from a sustainability perspective, there is now a critical need to enhance agroforestry systems, the time has come in developing strategy to tailor plant genetic resources programs to address immediate needs. These very clearly need to build on the distinction made above for plant introduction and for genetic use. Of the materials used for gene sources there is the even greater need to accelerate the collection, conservation, and in parallel, the selection and breeding, of multipurpose tree species that will enhance the supply of food supplements, fuelwood, materials for building, and other local uses of poor farmers. Bamboos, although not trees, need high priority in this area. Fortunately, mosr multipurpose trees produce seeds that can be stored so that conservation for future needs can be relatively cost effective. This is not yet the case for bamboos because of erratic flowering. Conservation methodologies will require more research. Many of the remarks related to agroforestry and sustainability issues

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have pointed to what should be done rather than what currently is done. However, for plant genetic resources research the technology is in place; it is simply a question of applying it practically when good strategic planning and funding are in place. B. PLANT GENETICRESOURCES RESEARCH FOR BIODIVERSITY CONSERVATION It is not the purpose of this article to discuss plant genetic resources in relation to nature conservation nor to the whole issue of preservation of biodiversity. The issues are widely known and have been summarized in a recent publication of the World Bank, World Resources Institute, IUCN, Conservation International, and WWF (McNeeley et al., 1990). Nonetheless, there are some significant areas where crop genetic resources specialists will increasingly be called on for expertise and cooperation. Some of these areas are presented here. 1. In situ preservation of certain plant genetic resources in “traditional” agricultural systems, particularly tree crops, is important. There is a need to see that these are managed as sustainable systems, not “alternative” agriculture. Agronomists have a large part to play in designing more sustainable systems. While it is true that agroecosystems may incorporate local varieties and that this can complement ex situ conservation, there is no guarantee of conservation in perpetuity (Sastrapradja, 1989). This method is likely to become used more for species that are not far removedfrom-wild species and those that are associated with rural habitations. 2. Keystone species of ecosystems may require specific attention as one element in conserving the whole. In some cases to ensure population continuation in situ some genetic management might be prudent (Frankel, 1983) and conservation of genetic stocks for such management might need to be a special concern of a national program otherwise aimed at storing crop variability. 3. New work on domestication of a limited number of underexploited species has received a lot of interest. Examples would be several neotropical palms, and one, peach palm, is already in production. More interactions are needed between crop scientists and those involved with conserving ecosystems.

For the past decade there have been discussions on the role of population genetics in conserving threatened species and managing reserve areas (Frankel and Soule, 1981; Schonewald-Cox et al., 1983; SoulC, 1987). The discussions and research have focused on methods to estimate the viable

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size of populations, criteria for management of populations, and the design of reserves in relation to geographical dispersion and maintenance of genetic variability. Soule in 1987 summarized the problems as long-term persistence without significant demographic or genetic manipulation for the foreseeable ecological future (usually centuries) with a certain agreed on degree of certitude, say 95%. However, this assumes that for the ability of a population to maintain itself in nature there is a normal level of immediate fitness and there is sufficient genetic variation to adapt to minor environmental changes and disturbances. Evidence from field work on the distribution of closely related species of woody crops, especially those that have widely scattered populations, shows a degree of fragility in relation to certitude of perpetuation. In these cases, and when ex situ methodology is not applicable, it is foreseen that protocols for genetic intervention will have to be developed. These will draw heavily on experience of horticulturists, agronomists, and genetic resources conservation. They will include, as examples: 1 . storage of pollen, freeze dried, for artificial pollination; 2. hybridization between diverse genotypes to provide recombinants for local, natural selection after planting of progeny; and 3. planned interplanting from other populations. Although there is a clear scientific basis for the comments above, no strategic research has been carried out, and the three examples cited are simplistic suggestions pending more data on relationships between measures of fitness and genetic variation, knowledge about when inbreeding depression and population bottlenecks occur, and other aspects of population dynamics. It is a new direction which must be followed quickly by conservation biologists and where genetic resources specialists and agronomists must be consulted at the initial planning stages. A useful reference from the conservation biologists is provided by the Society of Conservation Biologists (Soule and Kohn, 1989). As a closing remark in relation to sustainability, it is salient to recall a lesson learned with a tropical crop, rubber. Leaving aside the problems related to its place in the world’s economy-with, at one, time an aggressive defense mounted against encroachments by synthetics, which proved untenable-reorientation of research and development has relied on two factors. First, there is the interdependence of the world in relation to resources, and second, there is modernization of small-holder operations with, on one hand, better planting materials and, on the other hand, better agronomy. These factors are basic to all future attempts at agroforestry and sustainable agriculture in most rural situations.

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V. CURRENT NEW DIRECTIONS IN GERMPLASM MANAGEMENT AND RESEARCH With many institutions working on germplasm across a very wide range of crops it is impossible in a short space to describe all the new directions in research. It is pertinent to group them under strategies and to provide references for further reading.

A. COOPERATIVE NETWORKING The development of a global network has been a major aim of F A 0 and IBPGR. Historical realities led to the designation of a number of centers that hold base collections for long-term seed storage; these centers and associated active collections need to be carefully linked. In recent years, IBPGR has been sorting out a conceptual framework based on proposals compatible with today’s political and financial realities (Perret, 1989; Marshall, 1989). Some of the main features outlined by Marshall follow. 1. A global network should include all significant collections, and there should be a special emphasis to include national collections as the primary source of most germplasm. 2. The concept of a few large base collections needs modifying. Each germplasm collection should have the responsibility for the long-term storage of materials unique to the collection. 3. The concept of separate base and active collections needs to be modified so that the network is a single network of collections; all will be active ones with selected ones assuming responsibility for longterm conservation of a specified set of germplasm. 4. National gene banks should be fully involved in policy making and international coordination. 5 . Participation would require a code of collaboration that includes free availability of materials and duplication of unique materials.

The functional unit would be based on crop-by-crop schemes, the crop networking referred to in Section II,A. Seminal to this is good databasing (Williams, 1984; Konopka and Hanson, 1985).

B. MANAGEMENT OF COLLECTIONS It has now become accepted that the selection of a subset of a large collection, as a core-with the major part banked for safety in long-term

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storage-can be a useful tool so that a manageable set of accessions can be worked on. The core should be a representative assembly based on ecogeographic origin and specific characteristics (Frankel and Brown, 1984; Brown, 1989). The selection of core collections should not be seen simply as developing a workable subset out of large collections, thereby negating the necessity of other aspects of management such as sorting out redundance and excessive duplication within and between collections (Perret, 1989). It can also be a useful management tool combined with better use of collections (Peeters and Williams, 1984; Williams, 1989).

C. SAFETY OF COLLECTIONS Most crops can be conserved as seed in seed storage gene banks; however, running such facilities can be costly. Hence, two areas of strategic research need to be pursued. First, a more cost-effective storage should be explored, for example, reducing seed moisture content and relaxing the degree of refrigeration, and storage using natural phenomena (e.g., permafrost). Second, the biggest use of seed of stored samples is in routine viability testing, and alternative nondestructive methods are needed. For conservation of other crops, other methods are needed. The conceptual framework for in uitro genebanks is well established but a great deal of research is needed before they can be implemented for more than a few crops (such as cassava, potato, apple, and pears). The past decade has seen the sorting out of principles (Withers and Williams, 1982, 1985) and the establishment of linkages to other genetic resources activities (Withers, 1989). Other sections of this article have pointed to the practical difficulties of managing collections of wild species and linking seed and in uitro conservation to materials conserved in situ.

D. LINKS TO APPLIED RESEARCH There has been much written about ex situ genetic resources work being justified by its applications and the need for better use of the materials conserved. In part this represents a misunderstanding of the methods currently used by breeders, whereby they tend, in the first instance, to use breeding materials with which they are familiar and which cause the fewest problems. Additionally the existing coliections need a great deal of “sort-

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ing out” and many more relevant characterizations and evaluation data generated. This is a lengthy and costly exercise (Williams, 1989). Germplasm collections are essential for much applied research at the molecular level, including genome mapping and studies of biodiversity. There are exciting challenges that will increase the utility of the collection for highly bred crops and rapidly enhance others that have not received a great deal of breeding attention. The dialogue between scientists involved with applied research and those with genetic resources will be a continuing process.

VI. CONCLUDING REMARKS The groundwork has been laid for a “system” to make genetic resources available and to conserve them for the future. In any system, embracing so many countries, institutions, and plant diversity, efficiency can certainly be increased by upgrading scientific standards and skills of those scientists involved. Many programs have started on the basis of good intentions but there is a duty to see that today’s poorly prepared partners are not tomorrow’s marginal workers. The future of a global heritage depends on the skills and productivity of the emerging work force to run an increasingly sophisticated system. The needs for rapid transfer of new technology and the forging of new partnerships is apparent from this article and this requires a new vision involving agronomists as well as breeders and research scientists. Against this vision stands a sobering reality: It is impossible to conserve everything, and only a small part of the system can be user-driven by breeders and others. The user-driven sector has been very successful in relation to staple crop gene pools; however, the need to preserve minor crops with a back-up in nature conservation is not user-driven. Additionally, the funding for crop genetic resources work has not grown to match even the needs of the 1980s, and estimates of funding are largely unchanged (Plucknett et al., 1987). One reason for this is that these funds are largely for development assistance. Trends in funding of relevant scientific research are worrisome since they have been transferred in many cases to molecular work. However, the future for plant genetic resources work is bright if the funding for scientific research can be targeted in a strategic way so that the development assistance part has a solid back-up of research and development. This, I believe, is the challenge for the 1990s and requires vision and new noncompetitive partnerships between agriculture, science, and wider conservation interests.

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REFERENCES Balick, M. J. 1989. In “New Crops for Food and Industry”(G. E. Wickens, N. Haq, and P. Day, eds.), pp. 323-332. Chapman & Hall, London. Bramwell, D., Hamann, O., Heywood, V., and Synge, H., eds. 1987. “Botanic Gardens and the World Conservation Strategy.”Academic Press, London. Brewkaker, J. L., and Hutton, E . M. 1979. In ”New Agricultural Crops” ( G . A. Ritchie, ed.), pp. 207-259. Westview Press, Boulder, Colorado. Brown, A. H . D. 1989. In “The Use of Plant Genetic Resources” (A. H. D. Brown, 0. H . Frankel, D. R. Marshall, and J. T. Williams, eds.), pp., 136-156. Cambridge Univ. Press, Cambridge, England. Burley, J., and von Carlowitz, P., eds. 1984. “Multipurpose Tree Germplasm.” ICRAF, Nairobi, Kenya. Chang, T. T., Dietz, S. M. N., and Westwood, M. N. 1989. In “Biotic Diversity and Germplasm Preservation” (L. Knutson and A. K. Stoner, eds.), pp. 127-159. Kluwer Academic Publishers, Dortrecht, The Netherlands. Chapman, C. G. D. 1985. “Genetic Resources of Wheat: A Survey and Strategy for Collecting.” IBPGR, Rome. Chapman, C. G. D. 1989. In “The Use of Plant Genetic Resources” (A. H. D. Brown, 0. H. Frankel, D. R. Marshall, and J. T. Williams, eds.), pp. 263-279. Cambridge Univ. Press, Cambridge, England. Clement, C. R., and Arkcoll, D. B. 1989. In “New Crops for Food and Industry’YG. E. Wickens, N. Haq, and P. Day, eds.), pp. 306-332. Chapman & Hall, London. Duvick, D. N., and Brown, W. L. 1989. In “Biotic Diversity and Germplasm Preservation” (L. Knutson, and A.K. Stoner, eds.), pp. 499-513. Kluwer Academic Publishers, Dordrecht, The Netherlands. Felker, P. 1979. In “New Agricultural Crops” (G. A. Ritchie, ed.), pp. 89-132. Westview Press, Boulder, Colorado. Frankel, 0. H. 1983. In “Conservation of Tropical Plant Resources” (S. K. Jain, and K. L . Mehra, eds.), pp. 55-65. Botanical Survey of India, Howrah. Frankel, 0. H. 1985. In “Proceedings of the International Symposium on South East Asian Plant Genetic Resources” (K. L. Mehra, and S., Sastrapradja, eds.), pp. 26-31. LIPI, Bogor. Frankel, 0. H., and Brown, A. H. D. 1984. In “Crop Genetic Resources: Conservation and Evaluation” ( J . H. W. Holden and J. T. Williams, eds.), pp. 249-257. Allen & Unwin, London. Frankel, 0. H., and Soule, M. E . 1981. “Conservation and Evolution.” Cambridge Univ. Press, Cambridge, England. Harlan, J. R. 1975. J . Hered. 66, 184-191. Hazell, P. B. R., ed. 1986. “Summary Proceedings of a Workshop on Cereal Yield Variability.” IFPRI, Washington, D. C. Holden, J. H. 1986. In “Summary Proceedings of a Workshop on Cereal Yield Variability” (P. B. R. Hazell, ed.), pp. 71-76. IFPRI, Washington, D. C. Ingrarn, G. B., and Williams, J. T. 1984. In “Crop Genetic Resources: Conservation and Evaluation” (J. H . W. Holden and J. T. Williams, eds.), pp. 163-179. Allen & Unwin, London. International Board for Plant Genetic Resources (IBPGR). 1986. “Genetic Resources of Tropical and Sub-tropical Fruits and Nuts (Excluding Musa).” IBPGR, Rome. International Board for Plant Genetic Resources (IBPGR). 1988. “Annual Report for 1987.” IBPGR. Rome.

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