The Conservation of Genetic Stock Collections
Genetic stocks are lines that contain various mutant alleles, chromosomal rearrangements, or other cytological abnormalities that are useful only for genetic and basic biological experimentation. They rarely, if ever, have any direct commercial value, but they are essential to much basic and applied research. The term genetic stocks is occasionally used (for example, in some of the Food and Agriculture Organization [FAO] debates) in a much broader context to include the advanced lines of breeders that are largely unrelated to genetic research endeavors. In this chapter, however, genetic stocks refers solely to stocks used strictly for research purposes.
This chapter first considers the species of agriculturally important plants, animals, and microorganisms for which significant genetic stock collections have been established. It reviews the locations of major collections and the types of institutions that maintain them and then the compositions of genetic stock collections and how they differ from the compositions of other germplasm collections. Finally, the special problems that genetic stock collections pose in terms of long-term conservation and the steps that need to be taken to ensure their long-term security are examined. Genetic stock collections of other classes of organisms that have no direct economic benefit but that are used solely for such purposes as research and teaching (for example, the mouse Mus domestica, the fruit fly Drosophila melanogaster, the coliform bacterium Escherichia coli, and the pink bread mold Neurospora crassa) are important and may face many similar problems, but they are not considered here.
IMPORTANCE AND USE OF GENETIC STOCK COLLECTIONS
Genetic stock collections are an important component of the total conserved genetic resources both of economically important species, such as corn (Zea mays) and yeasts (Saccharomyces sp.), as well as of organisms used purely for research, such as fruit flies (Drosophila sp.) and bread molds (Neurospora sp.). Such collections have been of critical importance to the rapid progress made in the science of genetics and its applications to plant and animal improvement over the past few decades. From this viewpoint, genetic stock collections and their contributions to scientific progress are under appreciated outside the genetic research community. Furthermore, the importance and value of genetic stock collections will find increasing use in the identification, location, and isolation of specific genes and their manipulation and transfer into economically important plants and animals for breeding programs using molecular genetics tools. Consequently, the perception that genetic stock collections are primarily a research tool of no direct economic benefit is likely to change quickly as the impact of the new biotechnologies permeate commercial agriculture.
In addition, advances in molecular genetics will provide new challenges and opportunities for genetic stock collections. Of particular importance in this regard is restriction length fragment polymorphisms (RFLPs) (see Chapter 7). To exploit this technology, however, breeders and geneticists require not only known genetic strains of the organism of interest but also the DNA (deoxyribonucleic acid) probes necessary to detect RFLPs. The quality, maintenance, and continued availability of publicly developed genetic stocks and DNA probes for RFLP detection will become an issue of growing concern to geneticists and breeders alike in both developed and developing countries.
GENETIC STOCK COLLECTIONS
International agencies and most national programs have placed little emphasis on conserving genetic stock collections, even those of economically important species. There are several reasons for this. First, genetic stock collections have usually been regarded as serving entirely different purposes—genetic research and teaching—that require different inputs and management strategies compared with those required by cultivar collections of crops or breed collections of domestic animals. Second, genetic stock collections are usually seen as providing no direct economic benefits to developing countries, and hence to be of little interest to international agencies, especially those whose programs and funding are directed toward the poorer developing countries. Third, the development of genetic stock collections
is an expensive and time-consuming process and depends on close interactions with sophisticated research programs. As a result, extensive genetic stock collections of most organisms are confined to developed countries.
Furthermore, genetic stock collections are generally regarded as the responsibility of individual research groups that have developed and maintained them on a purely ad hoc basis. Only when the demand for access to genetic stocks and the size of the collections exceed the capacity of the individual researchers have there been moves to develop integrated national or international collections. Efforts to develop such recognized genetic stock collections have usually been initiated through scientific societies such as the Genetics Society of America and the Organizing Committees of the International Wheat and Barley Genetics Symposia.
Significant genetic stock collections exist for the major crop plants and microorganisms of economic importance in agriculture and medicine (Table 9-1). For the other groups of species, small to modest genetic stock collections have often been established, but they have not been developed to the same degree as those for crop plants, because of the lack of a long-term research effort in genetics and breeding or the lack of appropriate long-term maintenance technologies.
In the case of microorganism collections, it is debatable whether they should be strictly regarded as genetic stock collections. Such collections often contain genetically well defined strains of microorganisms for particular traits (for example, in the case of wheat rusts, virulence against specific crop cultivars). However, they are perhaps more akin in composition and use to cultivar collections for crop plants rather than genetic stock collections. On the other hand, in terms of problems of maintenance and long-term security, they have more in common with genetic stock collections.
Most genetic stock collections have been developed and maintained in the industrialized countries of the north, which have a history of strong scientific research programs in genetics, biology, and medicine. However, even in these developed countries, genetic stock collections have not received the recognition they deserve and frequently lack adequate financial support. Consequently, many such collections face problems of management, availability of information and materials, and long-term security of conserved stocks.
Development and Location
Genetic stocks have been developed by scientists as aids to basic research, therefore, they therefore differ dramatically in origin from
TABLE 9-1 Agriculturally Relevant Genetic and Microbial Stock Collections
the usual components of germplasm collections, which principally come from collecting missions or applied breeding programs. The development of a major genetic stock collection usually takes many decades and involves research and publication of results by many individual scientists. Initially, in the evolution of such collections, individual scientists develop and maintain particular stocks or classes of stocks of direct relevance to their personal research.
Development of Genetic Stock Collections
As investigators require the same or similar genetic materials for research, certain researchers or institutions usually become recognized as the primary sources of those stocks. If demand continues to grow, such individuals or institutions may develop into nationally or internationally recognized genetic stock centers. However, once the demand for genetic stocks has grown past the point at which individual researchers are willing or able to maintain sufficiently well-characterized material to meet the demand, efforts are usually made to develop a formal genetic stock center. One approach is to develop a center at one institution that handles all stocks of a species. An alternative approach is to develop a completely decentralized system in which scientists from many institutions agree to maintain and supply a designated class of genetic stocks.
Since genetic stocks are principally developed and maintained by research scientists, most are held in universities or research institutes. This is in contrast to germplasm collections for crop plants, which are usually maintained by national governments because of their strategic importance to national economics.
Maintaining Genetic Stock Collections
The fact that genetic stock collections are largely maintained by individuals within universities and research institutes has important implications in terms of continuity of funding and long-term security. Initially stock collections are usually funded as part of a research project, but once they grow in size, funds for maintaining the collection must compete with other aspects of the research program. Even when collections achieve national or international status, financial support may not be assured, because maintenance of collections is usually regarded by research funding bodies to be mundane and unproductive, in terms of publishable research results, and of low priority.
The maintenance of genetic stock collections by part-time curators
in research institutes, where they must compete with other activities for funds, is seen by some to have significant advantages. It is impossible to conserve all genetic variants of any species. The present system allows flexibility and forces the genetic stock collections to evolve in response to the needs of the user community. Under this view, the development of a more centralized system, in terms of funding and management, carries with it the danger of developing large collections with mainly historic entries of limited value to current researchers. The disadvantage of this view is that stocks of little interest today may become extremely important tomorrow. For example, the transposable element stocks from the work of Barbara McClintock were mere historical curiosities in the late 1950s, but they have become the center of attention for gene isolation and cloning today.
Components of Collections
Many different types of genetic stocks are used in biologic and agricultural research. Genetic stocks can be conveniently divided into three groups: single-gene or single-trait variants, cytogenetic stocks, and other genetic stocks.
Single-Gene or Single-Trait Variants
In the group of single-gene or single-trait variants, there are three subgroups. The first is morphologic and physiologic variants. Although the importance of some of these stocks may have been reduced with advances in modern molecular genetics, many are still of value as genetic markers and in studies of gene function—more valuable today for molecular research than they are for classical genetic studies.
The second subgroup is electrophoretically detectable protein variants. The use of electrophoretically detectable variants at genetic loci governing the production of specific proteins has increased dramatically over the past two decades in many spheres of genetic research. Consequently, genetic stocks carrying well characterized variants have become an increasingly important component of genetic stock collections.
The third subgroup is made up of variants with different RFLPs. The use of RFLPs as genetic tools in applied agricultural research will undoubtedly increase markedly in the near future. The identification and maintenance of genetic stocks carrying known genetic markers as well as the probes (DNA segments) used to detect them will become priority tasks.
There are three types of cytogenetic stocks. The first is variants with different chromosome structures. Variants whose chromosome structures differ from the norm because of deletion, duplication, inversion, or translocation of specific DNA segments from one chromosome to another are important in gene mapping, determination of the chromosomal location of specific genes, and studies of chromosome structure and function.
The second type is variants in chromosome number. These may include, particularly in plants, changes in whole genomes (haploids or polyploids) or changes in the number of a single chromosome, chromosome arm, or chromosome segments (nullisomics, monosomics telosomics, trisomics, or tetrasomics). Such variants are also valuable in genetic mapping and in basic genetic studies, such as in the study of genetic architecture of chromosomes.
The third type of cytogenetic stock is alien and substitution lines. The wild and the weedy relatives of the major crops are sometimes used as germplasm sources in breeding programs. A first steps is often the transfer of individuals chromosomes, or chromosome segments, carrying identified genes of potential economic importance into the crop species. The three types of alien chromosome segments used to transfer the desired gene into commercial crop varieties are addition lines, and translocation lines.
Other Genetic Stocks
There are also three types of other genetic stocks. One type is multiple gene stocks in which a particular chromosome carries multiple genetic markers that are particularly useful in linkage studies.
A second type is near isogenic lines that carry alternative alleles at specified loci. In near isogenic lines, alternative alleles at a locus are transferred by repeated backcrossing into the same genetic background. Such lines have been used principally in studies of the comparative effects of different alleles in similar backgrounds, but more recently, they have attracted increased attention from scientists interested in identifying and isolating genes and gene products.
Wild relatives of crop plants are a third type. Wild relatives of crop plants that are difficult to grow or manage within the framework of a normal cultivar collection or germplasm bank may be more readily maintained in genetic stock collections. These stocks need special management because seeds scatter at maturity. Most wild relatives of wheat, barley, and maize belong to this group. Other
examples are the wild species of Solanum and Lycopersicon held in the tomato genetics stock collections.
Breeding Lines Versus Genetic Stock Collections
A central theme of the FAO International Undertaking on Plant Genetic Resources (see Chapter 14) is that all plant germplasm should be available for exchange without restriction. Many countries, especially those that have significant privately funded plant breeding programs dependent on some form of proprietary protection such as patenting, are unable or unwilling to guarantee the free availability of privately held germplasm.
This controversy has focused on genetic stocks. The reason is that FAO's undertaking defined plant genetic resources as the reproductive or vegetative propagating material of the following categories of plants: (1) cultivated varieties (cultivars) in current use and newly developed varieties; (2) obsolete cultivars; (3) primitive cultivars (landraces); (4) wild and weedy species, which are near relatives of cultivated varieties; and (5) special genetic stocks (including elite and breeders' advanced lines).
This system of classification was developed in the mid-1960s (Frankel and Bennett, 1970) and emphasized crop cultivars and wild and weedy relatives of crops because of their importance in plant introduction and breeding. The category of special genetic stocks (category 5 above) includes all plant germplasm not included in the other categories, hence it includes genetic stocks and breeders' advanced lines. Genetic stocks and breeders' lines have several features in common that underlie their inclusion in category 5. For example, both are usually developed by individuals, often at considerable expense and personal effort. During development, the individual may choose to maintain exclusive control of such germplasm. Moreover, neither genetic stocks nor advanced breeders' lines are commonly held in most germplasm collections. Their status differs substantially from those of released cultivars or wild and weedy relatives, in that for the germplasm of wild or weedy relatives there is either no single identifiable originator or the originator, in seeking public release, has voluntarily forfeited exclusive control, at least for further breeding and scientific research purposes.
There are substantial differences between advanced breeders' lines and genetic stocks, however. Advanced breeders' lines are the elite materials from which a breeder selects new cultivars for commercial release. Consequently, they are often of substantial economic value, which is why their control and availability have generated controversy.
Genetic stocks, on the other hand, are seldom of direct economic importance, and their value lies in their role in scientific research. Except in their early days of development, genetic stocks are usually held in the public domain and are freely available (usually in very small quantities) on request. As defined here, genetic stock collections do not include advanced breeders' lines. Rather, they contain genetically defined stocks principally of interest to researchers rather than to plant breeders.
MAINTAINING GENETIC STOCK COLLECTIONS OF AGRICULTURAL CROPS
The conservation of genetic stock collections require technical and scientific inputs and physical resources broadly similar to those required for maintaining germplasm collections or agricultural crops. In the case of seed crops, for example, these broad requirements include the following:
Suitable low-temperature, low-humidity facilities;
Access to back-up storage facilities;
Adequate seed-handling facilities for drying, cleaning, packaging, and viability testing of seed samples; and
Computerized information storage and retrieval systems.
Special Needs and Requirements
Genetic stocks require highly specialized knowledge, procedures, and care for adequate regeneration and maintenance. For example, many stocks are weak, semilethal, or completely or partially sterile in homozygous condition, and in practice, they must be maintained in a heterozygous condition. Albino mutants are one obvious example. Some stocks may not routinely survive in the field and need to be grown in a greenhouse, whereas others may need special treatments (long days or vernalizing temperatures) before they flower or may require genetic or cytological screening. Genetic stock collections are difficult, and sometimes impossible, to maintain as part of national or international germplasm collections.
Curators of germplasm collections are reluctant to accept responsibility for genetic stocks if they lack the skills or resources to provide the specialized maintenance procedures required. Offers of additional training, staff, or resources seldom accompany requests for germplasm collections to take responsibility for the maintenance of genetic stocks. Similarly, users of genetic stocks are reluctant to have
such materials incorporated into germplasm collections, because experience has indicated that they quickly become contaminated or lost.
The maintenance of genetic stock collections by active researchers overcomes the problem of the need for specialized skills in the regeneration of genetic stocks but might create other difficulties with respect to long-term conservation. Institutes that take responsibility for or house genetic stock collections often lack suitable medium- to long-term, low-temperature seed storage and related drying, packaging, and computing facilities routinely available in first-class germplasm banks. The curators of genetic stock collections that lack such facilities are forced to regenerate their stocks repeatedly, despite the difficulties and dangers that this implies, to avoid the loss viability. In such situations, the total number of stocks that can be effectively maintained by a single curator is relatively small, and the cost per accession is relatively high.
The major source of funds available for maintaining genetic stock collections in universities and research institutes is competitive research grants. This support is vulnerable to short-term changes in funding policies as well as changing perceptions of what constitutes competitive front-line research. Indeed, the maintenance of genetic stocks is already regarded by some funding bodies as a low-priority area that should be funded on a long-term basis by appropriate government departments.
Commitment to the maintenance of genetic stocks in universities or research institutes is usually made by the individual researcher, not by the university or institute as a whole. Consequently, the continuation of collections may jeopardized if the research interests and commitment of the curator change or the institution changes the responsibilities of the position if the current curator resigns, retires, or dies.
Genetic stock collections have periodically come under serious threat of disruption, loss, or closure. Many important genetic stock collections have been maintained indirectly through support for other areas of research and by agencies not charged with the duty of their maintenance. In view of the importance of genetic stock collections in underpinning genetic and biotechnological research and the investment that has gone into the development of such collections, a number of actions have been taken to put at least some of them on a firmer long-term footing.
In the United States, the Genetics Society of America established the Committee for the Maintenance of Genetic Stocks (CMGS) in 1958. This committee served previously to alert geneticists to situations in which valuable collections of stocks were endangered by the lack of
adequate support or supervision. In the recent past, however, the CMGS has sought to play a greater role in developing objective criteria to be considered in determining which genetic stock collections warrant priority support and in promoting coordinated national support for priority centers.
The U.S. National Plant Genetic Resources Board has also considered the issue of long-term funding for genetic stock collections and has supported the concept that the U.S. Department of Agriculture (USDA) should be the agency that assumes the lead role and responsibility for the maintenance of genetic stocks of commercially important plants as part of the U.S. National Plant Germplasm System. USDA has provided full or partial support for several important genetic stock centers, for example, those for soybeans, peanuts, and tobacco; and in recent years, it has provided partial support for several others, including barley, maize, and tomatoes, as part of the U.S. National Plant Germplasm System (NPGS). Largely as a result of the efforts of USDA, it can be argued that, at least with respect to the major economic plants, genetic stock collections in the United States are as well maintained as they are anywhere in the world. Discussion of the role of the NPGS in maintaining important U.S. collections of genetic stocks can be found in an earlier report of this committee (National Research Council, 1991a). Nevertheless, significant problems of continuity and adequacy of funding and the management of genetic stocks of these species remain.
Two examples follow to illustrate the types of problems confronted by genetic stock collections.
EXAMPLES OF GENETIC STOCK COLLECTIONS
Management of genetic stocks collections presents a variety of technical, managerial, and financial challenges. The following profiles of two large genetic stock collections illustrate the need for competent, technically sound management, and the importance of cooperative efforts from the broad scientific community.
The Charles M. Rick Tomato Genetics Resource Center
This center, referred to here as the Tomato Genetics Stock Center (TGSC), was originated and developed by Charles M. Rick of the Department of Vegetable Crops at the University of California, Davis, principally as by-product of his research on the genetics, evolution, and breeding of this crop. Davis is near the center of the largest tomato-growing area in the world, and in 1987 nearly one-quarter of
the world's processing tomatoes were grown in eight counties within a 129-km radius of Davis. As a result, tomato genetics research and improvement has been carried out at the University of California, Davis, and in nearby private farms over many years to meet the needs of this large and economically important industry.
The TGSC arose from Rick's early investigations of chromosomal and genetic variants found in spontaneous unfruitful plants in commercial crops. The early surveys of commercial crops yielded a wide range of stocks such as haploids, triploids, and tetraploids as well as sterile diploid mutants that included many different monogenic mutants. This research subsequently led to a program of linkage mapping that generated a large array of additional mutants, linkage testers, and other stocks in which various markers were combined. In addition to collecting spontaneous mutants, genetic variants were generated by chemical mutagens, X rays, and fast neutron bombardment. Over time, the collection was also enriched by acquisitions of valuable genetic stocks from other research centers in the United States and other countries (Rick, 1987).
The accessions of wild taxa, the second major group in the TGSC, can also be traced largely to Rick's research activities. These include samples of the nine known species of Lycopersicon and four closely allied species of the genus Solanum. Rick's first trip to South America, where the tomato and its relatives were native, was in 1948. Since that time he has made 12 major expeditions to various parts of the world to collect wild germplasm. Other investigators have contributed accessions from their plant exploration and collection activities.
The TGSC collection has about 2,900 accessions. The principal components include some 700 lines carrying monogenic traits such as morphological variants, male sterility, resistance to pests and diseases. 800 linkage testers, chromosomal stocks and other miscellaneous lines, and 1,000 accessions of wild species.
For most of its existence, TGSC was supported largely by its host institution, the University of California, as part of its overall research and teaching program. Additional support came from grants from the National Institutes of Health and the National Science Foundation for research on the acquisition and maintenance of relevant genetic stocks. As TGSC increased in size additional resources were required. Initially, funds were sought from the National Science Foundation, and a grant of $96,500 was awarded for the 3-year period from 1976 to 1979. A second grant of $109,369 was received from the National Science Foundation for the period from 1979 to 1982. Subsequently, support was sought from the Agricultural Research Service (ARS), U.S. Department of Agriculture, which has provided an
average of $40,000 per year from 1982 to the present. Beginning in 1985, the Genetic Resources Conservation Program of the University of California has provided an average of $6,700 per year. An endowment, donated primarily by industry, supplies additional funds.
Operations of the TGSC
The TGSC is responsible for the maintenance, regeneration and increase, dissemination, cataloging, and data management of the accessions it holds.
Maintenance of Stocks All accessions are stored as seed at 8¹under 35 percent relative humidity. Entries are maintained in a working collection and in a duplicate collection maintained under the same conditions as a conservation measure. While the longevity of the accessions varies with species and genotype under these conditions, most can be stored for 20 to 25 years. As a further safeguard, reserve samples are also stored at the National Seed Storage Laboratory (NSSL) of the ARS at Ft. Collins, Colorado. Replacements and additions to accessions already in the NSSL are made each year.
Seed increase About 300 stocks, on average, must be increased each year. There is no uniformly applicable procedure for seed increase because of the genetically diverse nature of the lines in the collection. For wild species it is TGSC policy to make a large seed increase of each new accession as soon as possible after collection or accessioning. In this way unnecessary regeneration with the attendant risk of altering the original genetic composition of the accession is avoided.
Dissemination of Seed Over a recent 5-year period, about 3,000 seed samples were distributed annually in response to about 225 requests from 175 scientists. Almost half of the requests came from scientists outside the United States. TGSC supplies seed free of charge and attempts to meet all requests for stocks. With the growth of molecular genetics and its potential impact on plant improvement, demand for genetic stocks will probably increase.
Accessioning of Stocks It is the practice of TGSC to maintain all stocks of bona fide aneuploids and mutants, that is, those for which convincing data have been published. Many compound-mutant stocks, developed for such purposes as gene mapping, are likewise accessioned. From 1983 to 1987, about 90 new stocks were added to the collection each year, of which about 55 percent came from outside the University of California, Davis, program. It is expected that the collection will continue to expand.
Data Management The growing number of accessions and the increasingly detailed information available on each accession means that data management is substantial and growing problem for TGSC. TGSC currently lacks a computerized information storage and retrieval system. Passport data are lacking and inadequate for the TGSC accessions stored at NSSL, and the TGSC collection inventory has not been entered into the Genetic Resources Information Network (GRIN) of the U.S. National Plant Germplasm System. A computerized data base compatible with GRIN is planned to service the management of TGSC and to make the updating of GRIN more efficient. It will also allow wider and easier access to the TGSC inventory by users.
The TGSC collections, like many other genetic stock collections, were developed primarily from the research of one person, C. M. Rick. Over the past 40 years the collection has evolved from a small number of accessions primarily used in Rick's personal research program to a very substantial number of accessions that are collectively of national and international importance. During this evolutionary process the TGSC changed radically in its responsibilities, facilities, and size. The evolution of TGSC was relatively smooth because of Rick's standing in both the scientific and industrial communities and the support he has received from the University of California and other resources.
Nevertheless, the TGSC faces ongoing problems. These include lack of long-term financial support, an ill-defined curator succession policy, and inadequate physical facilities.
A task force involving members of the University of California Department of Vegetable Crops, the University of California Genetic Resources Program, and private companies concerned with tomato improvement was established to review the present and future funding, personnel, and space needs of TGSC. Based on this review, the task force sought to outline a suitable management structure, to identify sources of stable long-term funding, and define optimum facilities for TGSC. The report of the task force has been published (Genetic Resources Conservation Program, 1988).
Barley Genetic Stock Collections
Barley geneticists and breeders have established an internationally coordinated network of centers for the maintenance of barley
genetic stocks. Under this scheme, individuals are appointed to coordinate maintenance of each of the different categories of genetic and chromosomal variants commonly found in barley. As of this writing, coordinators have been appointed for 17 different classes of genetic stocks.
The coordinators' responsibilities include the maintenance of as complete a collection of their particular type of stock as possible. They also supply seeds to other researchers on request, compile up-to-date information on the stocks in their collection, and prepare an annual report for the Barley Genetics Newsletter.
Individuals are also appointed to coordinate work on each of the seven barley chromosomes. These coordinators are responsible for updating the linkage map of their designated chromosome using published data, information provided directly by barley researchers, or data from their own studies. The revised linkage maps are also published regularly in the Barley Genetics Newsletter.
In addition to the coordinators for the different genetic stocks and barley chromosomes, there is an overall network coordinator.
The development of a dispersed, but coordinated, network of genetic stock collections for barley occurred because of the widespread economic importance of this crop and because of the long-standing genetic and breeding programs on barley that are in place in many countries. Barley is excellent subject for genetic studies because it is an annual plant, predominantly self-pollinated, with a small number of chromosomes (N = 7), and has a large number of easily classifiable marker loci. Thus, substantial genetic stock collections were established in different research institutes throughout the world. As the collections grew in size, efforts were made to increase cooperation among them to minimize duplication of effort and to ensure that those with a special interest and expertise in any given group of genetic stocks were closely involved in their maintenance. The present system was formally put in place by the Committee for Nomenclature and Symbolization of Barley Genes at the Second International Barley Genetics Symposium held in Pullman, Washington, in August 1969 (Robertson and von Wettstein, 1971).
It is not possible to consider here all the elements of the international system for the maintenance of barley genetic stocks. Consequently, this discussion is limited to the collection held by the Department of Agronomy, Colorado State University, Ft. Collins. This collection, designated the World Barley Genetic Stock Center by the First International Barley Genetics Symposium, Wageningen, The Netherlands, in 1963, plays an important role in coordinating the maintenance of barley genetic stocks in the international network.
The Barley Genetic and Aneuploid Stock Collection
The Barley Genetic and Aneuploid Stock Collection (BGASC) in the Agronomy Department at the Colorado State University, Ft. Collins was established by D. W. Robertson and his colleagues as a resource for genetic linkage studies in barley. These studies began in the 1920s and emphasized simple morphologic marker genes of value in early linkage studies. Over the years the collection was enriched by the addition of a wide range of naturally and artificially generated variants, linkage testers, and more recently, of cytogenetic stocks from the local program and others in the United States and overseas. Unlike TGSC, BGASC does not maintain stocks of wild relatives. These are maintained as part of the USDA barley germplasm collection.
The size of BGASC has varied over the years as new materials are sent to the collection, tested for allelism, and discarded or accepted into the collection. There are now over 3,000 accessions in the collection.
Throughout its existence, BGASC has been supported principally by Colorado State University, Ft. Collins. Additional support came from grants from the National Science Foundation from 1961 to 1979. USDA has provided financial support since 1979 to ensure the continued operation of the center.
The center also received partial outside support for the publication of the Barley Genetics Newsletter as an informal international communications medium in barley genetics. Initially, in 1971, three European countries, Denmark, the Federal Republic of Germany, and Sweden, supported 50 percent of the cost of publishing and distributing this newsletter. However, this arrangement was terminated in 1986. Consequently, in 1987 the American Malting Barley Association took responsibility for the publication and distribution of the Barley Genetics Newsletter.
Operations of the Barley Genetic and Aneuploid Stock Collection
The BGASC is responsible for the maintenance, regeneration, dissemination, accessioning, and data management of its materials. As designated world collection, it seeks to maintain a sample of all accessions held in the network.
Maintenance of Stocks All accessions are maintained in a working collection of Ft. Collins, Colorado. As a safeguard, additional samples of some stocks are also stored in the National Seed Storage Laboratory, USDA, which is located on the Ft. Collins campus of Colorado State University. A program is also under way to duplicate the entire collection.
Some 300 genetic stocks that have been well studied genetically are considered to be active stocks. These are frequently requested by researchers throughout the world and are regenerated more often to maintain enough seed for distribution.
The list of these stocks is published in most of the issues of Barley Genetics Newsletter and Genetic Maps (National Institutes of Health, Bethesda, Maryland).
Seed Increase Much of the collection was increased during the period from 1969 to 1971. Stocks have been increased since then according to demand. However, recently a systematic growing out of the entire collection was begun. The stocks are mainly grown in the USDA-ARS greenhouse in Ft. Collins. About 300 to 500 stocks are grown each year, and a sample of all seed is supplied to the National Seed Storage Laboratory for long-term conservation.
Trisomic and other aneuploid stocks are routinely increased as part of the research program. In the case of trisomic stocks, chromosome counts are made for every plant, because only approximately 30 percent of the seeds harvested from trisomic plants are trisomics; the rest are normal diploids.
Accessioning of Stocks BGASC maintains stocks of at least two alleles of all defined loci as well as aneuploid stocks and stocks with multiple genetic markers useful in gene mapping. Although it would be desirable to maintain stocks of all reported variants, the numbers are so large that it is impossible. Because of limited resources, the policy of the BGASC is to maintain only one mutant or variant stock per locus. Allelism tests are carried out to identify those stocks to be retained in the collection. With some exceptions, no stocks are accepted at present because of uncertainty about the long-term future of BGASC.
Data Management Updated lists of the stocks held by BGASC are published periodically in the Barley Genetic Newsletter and Genetic Maps. The center encourages geneticists who identify new mutants to publish detailed descriptions, according to a standard format, in the Barley Genetic Newsletter. This ensures that an adequate description is readily available and frees the BGASC from unnecessary record keeping. However, if new mutants are not acquired by the BGASC, they are unlikely to be maintained other than by the people describing them.
No description has been published for the majority of stocks maintained at the center. Some information was obtained when an entire collection was grown during the period from 1969 to 1971. Detailed records are again being acquired during the current program of stock
regeneration and increase. These records may be added to the GRIN network. Similarly, if funds are available, these data could be published as a special issue of Barley Genetics Newsletter, together with a listing of the complete collection.
Like TGSC, the BGASC has grown in size and scope over the last half century. It now represents a resource of considerable national and international importance and plays a pivotal role in coordinating the international network of genetic collections for barley. BGASC has also faced a major funding crisis in recent years because of the loss of National Science Foundation funding and the loss of European support for the Barley Genetics Newsletter. It has been able to arrange alternative funding from the USDA and private industry, respectively, so prospects for the immediate future are promising.
TOWARD A MORE SECURE FUTURE
Genetic stock collections are an important complement to genetic resources collections. Genetic stocks are essential to an understanding of the genetic structure of a species, and this basic knowledge is of importance in enhancing the effectiveness of plant improvement programs. As a consequence, it is likely that demand for well-characterized genetic stocks from geneticists, biochemists, physiologists, and biotechnologists will increase in the future.
The requirements for conserving genetic stocks and germplasm collections are similar. Nevertheless, the maintenance of genetic stocks poses a number of unique problems because they are often difficult to regenerate and frequently require specialized expertise and extraordinary care in terms of their genetic identity and characterization. As a consequence, the maintenance of genetic stocks and regular germplasm collections have usually followed separate paths.
Important collections of genetic stocks must be provided a secure base of financial and technical support.
Germplasm collections have generally been maintained by the major public institutions involved in crop improvement. In contrast, the maintenance of genetic stocks, even those of the major crops, were undertaken on a voluntary basis by individual scientists or groups
of cooperating scientists, usually with the support of research institutes or competitive research grants. This system has generally worked well. There are, however, major problems, particularly with respect to the continuity of financial support, data storage and management, and the relationship between genetic stock and germplasm collections.
It needs to be emphasized, however, that the changes made should not be at the expense of flexibility. The prime function of genetic stock collections is to provide materials for research. Therefore, the composition of the collection must evolve with research needs. The changes also should not be at the expense of stock quality which is critical for reliable research results. To accomplish this, management of genetic stock collections must continue to be the responsibility of specialist scientists.
For many genetic stock collections, the provision of dependable long-term funding remains the single most important issue threatening their future security. The situation in the United States has improved in recent years, principally because an increasing number of genetic stock centers have been brought under the umbrella of USDA, as illustrated above for TGSC and BGASC.
Directors of germplasm centers often do not recognize the length of time and long-term apprenticeship necessary to become familiar with genetic stocks. Even reasonably complete documentation cannot cover the intricacies of growing, crossing, and maintaining the temperamental stocks that are found in genetic stock collections. Thus, the costs of arranging transfers of genetic stocks to germplasm centers are almost always greatly underestimated in terms of both time and effort. Only together can genetic stock and germplasm collections claim to represent the total spectrum of genetic variation in a species, and while there are good and valid reasons for their separate existence, there are no good reasons for the lack of cooperation and coordination that would enhance support for both types of collections.
With better long-term funding, improved data management facilities, and greater coordination with germplasm banks, genetic resources centers would provide genetic stock collections with the stability and security they need to meet the challenge of the rapid advances in molecular genetics likely to occur into the twenty-first century.
Major collections of genetic stocks should be overseen by an advisory board of qualified experts in genetics, breeding, and seed storage.
There are problems in deciding which collections deserve priority support as national or international resources. The important factors
in reaching such decisions are the extent of and potential for use of the collection, the quality of material supplied to the users, and the costs of its maintenance. Advisory boards can help with policy development in the areas of stock acquisition, discarding unnecessary or redundant materials, and coordination with other genetic stock or genetic resources collections. Such boards can also play an important role in developing a succession policy for the center that can be put in place, allowing it to continue to operate effectively when key professional staff leave or retire.
Storage and retrieval of data for genetic stocks must be computerized.
Data collection, management, and distribution also remain problem areas for genetic stock collections. The major genetic stock centers generally produce periodic newsletters, one of the functions of which is to provide users with up-to-date information on the status of the collections. However, many centers have been slow to computerize storage and retrieval systems for data management. Modern facilities could lead to substantial improvements in access to information and stocks. At genetic resources centers, computer software packages have been developed and are in use internationally.
Coordination of the activities of genetic resources centers and genetic stock collection have often been poor. The lack of duplicate samples deposited to long-term seed stores remains a major deficiency. Documentation is almost always inadequate.