Abstract. Concepts for the treatment of duplication and sharing of responsibilities in ex situ collections are ..... they have been referenced in scientific publications.
Genetic Resources and Crop Evolution 50: 693–705, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands.
693
Concepts and data models for treatment of duplicate groups and sharing of responsibilities in genetic resources information systems 2 ¨ Christoph Ulrich Germeier 1, *, Lothar Frese 1 and Stefan Bucken 1
Federal Centre for Breeding Research on Cultivated Plants ( BAZ) - Gene Bank, Bundesallee 50, 38116 Braunschweig, Germany; 2 KWS SAAT AG, Grimsehlstr. 31, D-37555 Einbeck; * Author for correspondence (e-mail: c.germeier@ bafz.de, l.frese@ bafz.de); (e-mail: s.buecken@ kws.de) Received 17 December 2001; accepted in revised form 14 April 2002
Key words: Duplication, Ex situ collections, Genetic resources, Information systems, International crop databases, Maintenance standards, Sharing of responsibilities, Storage management
Abstract Concepts for the treatment of duplication and sharing of responsibilities in ex situ collections are developed with regard to the design of a documentation system. Large amounts of duplication are found in European genebanks especially with obsolete cultivars. If internationally registered they will reach several national genebanks from respective cultivar registration authorities collaborating with genetic resources collections. Rationalisation of collections and reducing work load with duplicates will be a precondition to keep high quality maintenance standards with diminishing resources. Sharing of responsibilities on an accession basis is the preferred procedure within the European Cooperative Programme for Genetic Resources Networks. Central crop databases play an important role in this process. A design of passport data is presented, which allows for compiling and extending information available for duplicate groups (genotypes) without affecting original multicrop passport information provided by holding genebanks for their accessions. Additional descriptors for responsibility, restrictions in availability and storage status agreed on by holders of duplicate accessions within the international considerations are included. Primary responsibility is mainly defined by fulfilling standards of maintenance and providing access to the germplasm. It includes holding a base sample, an active, publicly available sample and a safety duplicate at partner genebanks. Considerable reduction of work load without discarding of accessions can be achieved by setting duplicates to a reference status implying maintenance of only a base sample with no or restricted public access. Abbreviations: ECP/ GR – European Cooperative Programme for Crop Genetic Resources Networks, EADB / IADB – European / International Avena Database, IDBB – International Database of Beta; MCP Multicrop Passport Descriptors
Introduction Genetic resources work started about 1890, when the value of landraces was recognised on the Agricultural and Forestry Congress in Vienna (Hardon 1999; Lehmann, C., 1990). First ex situ collections were founded 1894 in Russia (Loskutov 1999), in the United States in 1898 (Mowder and Stoner 1989) and 1943 in Germany (Lehmann, C., 1990). Despite suggestions of FAO and IBPGR-IPGRI coming up in the
1960s and 70s for a regional organisation of conservation of genetic diversity, the situation especially in Europe has been dominated by a multitude of national programmes for maintaining genetic resources. Currently 500 genebanks, which represent 38% of 1308 world genebanks are found in 13 Western and 17 Eastern European countries. They contribute 35% of world’s genebank accessions (Engelmann and Engels 1999). Due to the national orientation of genebanks and seed exchange between national multicrop
694 genebanks, a lot of duplication of accessions accumulated. All genebanks have a prevailing tendency to maintain large and comprehensive collections of their own at least for those crops, which the national breeders are working with. This is more driven by lack of information on material available from other countries than lack of trust in each other (Gass et al. 1997). Lyman (1984) estimated at least 50% of germplasm accessions kept in genebanks world wide being duplicates. Similar estimations have been cited in a technical conference paper on plant genetic resources in 1996 (FAO (Food and Agriculture Organisation of the United Nations) 1996). With raising costs and diminishing resources, especially working capacity, it became evident, that rationalisation of collections will be a precondition to keep to high quality of maintenance standards. Within the European Cooperative Programme for Genetic Resources Networks (ECP/ GR) this resulted in an upcoming discussion on rationalisation of collections by searching for duplicates in the collections of the various genebanks and sharing of responsibilities for duplicate groups. Three basic approaches were considered for rationalisation of collections and sharing of responsibilities (Gass and Begemann 1999): 1. Sharing of responsibilities on a crop by crop basis 2. Sharing of responsibilities on a regional or subregional basis 3. Sharing of responsibilities on an accession basis Gass and Begemann (1999) outlined the central role of central crop databases in the process of sharing of responsibilities especially on an accession basis. About 35 European central crop databases have been established within the ECP/ GR (Gass et al. 1997) for providing a comprehensive overview of the collections maintained in Europe and allowing the cropspecific working groups to take informed decisions regarding the need for safety duplication, characterisation, rationalisation and sharing of responsibilities in conservation activities, filling of information gaps and planning of further collecting activities. A primary need in setting up these databases is finding standardised concepts and terminology in genetic resources data documentation. First attempts were made in 1996 regarding a standard table for passport data exchange called the Multicrop Passport Descriptors (Hazekamp et al. 1997). Remodelling the documentation system of BAZ ¨ Gene Bank (Bucken and Frese 2000) and two international crop databases (International Database of Beta
(IDBB) and European / International Avena Database (EADB / IADB)) we found a relational database design most suited for modelling the complex interrelationships in genetic resources data documentation (passport, characterisation and evaluation data) and genebank management (seed stock management, viability testing, seed transactions). Additional principles of a ‘human database design’ have been outlined in Koch and Loney (1995): Database objects should be named with meaningful, memorable, descriptive, short and singular English words. Codes, abbreviations and underline should be avoided. Naming of database objects of different levels (e.g. tables and columns) should not be mixed. Identifiers for data sets (keys) should be given meaningful and easily understandable values wherever possible. In this paper we will communicate concepts of database design and terms coping with duplication in ex situ collections and duplicate groups, with responsibility for accessions, with base and active collections and safety duplication. It is intended to present a relational design of tables on these items and to suggest some new standards in terminology. Their understanding will be necessary in starting up the sharing of responsibilities processes intended for the European Beta and Avena collections. The Multicrop Passport Descriptors (MCP) as defined by Hazekamp et al. (1997) form the core of this system. Nevertheless some modifications in MCP terminology are suggested for clarification of terms.
Duplication exemplified in IDBB and EADB The origin of a genebank accession generally should be identified by a collecting number represented in a defined collecting expedition, a breeding stock number assigned by a certain breeder or developer and / or an accession (cultivar) name. Most duplication is found with cultivar names as can be seen in Table 1 for Avena spp. in the EADB and for Beta spp. in the IDBB. Accession names like ‘Avena’, ‘Taubhafer’, ‘Red Rustproof’, ‘Jari Oves’, ‘Local’ etc., which are not useful for identification of a genotype, have been already omitted within this quantification. Table 1 refers only to completely identical names or collecting numbers and restricts counting to accessions held in different genebanks. Sometimes accessions are even duplicated within a single genebank. Further duplication will be found when misspelling or even translation of cultivar names into other languages is taken
695 ¨ cultivar into account. Thus it is known that Svalof’s ‘Seger’ has been entered into the French catalogue as ‘Victoire’, the cultivar ‘Oern’ as ‘Aigle’ (Moule 1964). Also ‘Adler’ and ‘Victory’ are entered in the EADB with a Swedish origin. Algorithms identifying more completely the amount of duplication have been ¨ suggested (van Hintum and Knupffer 1995) and are currently implemented into our international databases. It is questionable, to what extent identical names have been given to different cultivars. Article 26 of the International Code of Nomenclature for Cultivated Plants (Trehane et al. 1995) forbids re-use of cultivar epithets. Nevertheless it is current practice in the EU to allow re-use of names after a fixed time (Green 2001 personal communication). Less duplication is found in the IDBB compared to the EADB, which may be partly due to the smaller size of the Beta collection but also due to a better documentation of collecting numbers. In the IDBB 5237 accession names and 4053 collecting numbers are documented. 644 accessions are identified by both accession name and collecting numbers, between them 37 accessions called Seskuolo, 31 called Acelga, 30 Pantzari, 29 Selek Bar, 24 Seskla etc., which are discerned by collecting numbers. It is questionable, if also those accessions should be treated as duplicates
since these vernacular names indicate types of material like ‘leaf beet’ or ‘garden beet’ rather than names for individual landraces. In the EADB 25215 accessions are entered with an accession name other than those mentioned above. Only 1803 collecting numbers are entered (at the right place) and only 99 accessions are identified by both accession name and collecting number.
A data model treating duplication in ex situ collections Treating the problem of duplication within the genebank network in central crop databases has to take into account the following facts: 1. Passport data describing the origin for a set of duplicate accessions (duplicate group) should be identical. According to the normalising concept in relational database theory this means that these common data should be extracted into a new table with only one entry for each duplicate group. 2. Compilation of duplicate groups is often highly hypothetical (van Hintum and Visser 1995) and based only on similarities in passport data (probable duplication, see below). Thus the database design has to allow for changing classification into
Table 1. Duplication in Beta and Avena accessions within the IDBB and the EADB EADB: Avena Identified by accession name Number of Holders Names 17 14 13 12 11 10 9 8 7 6 5 4 3 2
1 2 8 14 21 31 60 69 120 148 210 296 462 951
Identified by collecting numbers Number of Holders Identifiers
2
5
Examples
IDBB: Beta Identified by accession name Number of Holders Names
Examples
Condor Marino, Pendek Mustang, Garry, Selma, . . . Flaemingsgold, Orion II, . . . Binder, Oern, Risto, . . . Eho, Stjaern, Sol II, . . . Sol I, Stormogul I, Seger I, . . . Jaune d’Artos, Eaton, Nip, . . . Regenfreund, Stormogul II, . . . Reine Vilmorin, Zlotniak, . . . Probsteier, Beseler III, S 84, . . . Carstens IV, Victory, Dukat, . . . Siegeshafer, Langgewens, . . . Grossmogul, Fulton, . . .
6 5 4 3 2
1 5 25 60 257
Detroit Saturn, Lucullus, . . . King Red, Ruby Queen, Puressa, Chotovka, . . . Nestor, Pezik, Peragis, . . .
Examples
Number of Holders
Identifiers
Examples
SUNGEORG-85: 1398, . . .
4 3 2
2 31 327
46, 11 8953, WB615, . . . TAV 270790 0201, . . .
696 duplicate groups without loss or change of original information. These items have been treated in our databases by dividing passport information into two major tables (Figure 1): GENOTYPE, which describes the origin or genetic identity of a duplicate group and ACCESSION, which describes individual accessions of a ‘genotype’ stored in different genebanks. The term ‘genotype’ does not imply genetic homogeneity. Depending on breeding system, sample status and scope of collection genotypes may be inbred lines, cultivars or wild material of self pollinating or outcrossing species or even heterogeneous populations as in the cases of landraces or multilines. Nevertheless they are genotypic entities defined by their passport descriptors. The GENOTYPE table holds most of the passport descriptors describing collection, breeding or cultivar registration of a genotype. Relevant geographic information (collecting site) is stored in a related SITE table. Further related tables connect modules for taxonomic, breeding and pedigree information and accompanying literature references, which will be described in further papers. Information is held in GENOTYPE and related tables in a standardised and corrected manner, compiling and taking into account all information provided by the genebanks holding the individual accessions. Thus duplication is also a chance for broadening the information base for a group of accessions. Normally these tables start out with taking over passport information from the best informant genebank for each duplicate group whereby ‘best’ means the most complete and correct passport data set. Further standardisation, correction and completion is achieved gradually by the central crop database manager and compilation algorithms in the database. The ACCESSION table gives information about duplicate status, responsibility of genebanks for accessions of a duplicate group, assignment of accessions to a core collection, number of user requests and similar information specific for a duplicate accession in a certain genebank. It also holds all original passport information contributed by the various genebanks holding the duplicate accessions in an original Multicrop Passport Format, which is assumed to remain with slight modifications as a standard exchange format for passport data. This redundancy with information in GENOTYPE and related tables is necessary to provide original as well as standardised and corrected passport information.
The latter is presented to the user, while original information should be provided on special request and in cases of doubt and disagreement. Incoming database updates will be first checked against the original information in the ACCESSION table, which will be updated with changed original information. In such cases, the database manager will be prompted to check, whether the new information could also improve describing information in other tables.
Terminology on duplication and responsibility for accessions in ex situ collections Biological and organisational determinants within the process of sharing responsibilities have to be discerned in the discussion. Biological categories of duplication have been described by Hintum van and ¨ Knupffer (1995). These are listed in Table 2 with three letter codes, which will be found in the descriptor ‘duplicate type’ within the ACCESSION table. It will not always be possible to assign a sample to one of the biologically meaningful categories shown in Table 2a, as the knowledge on the origin of a sample as well as the maintenance history having great impact on the genetic composition of a duplicate accession can be obscure. But if details on the samples history are known, it can facilitate decisions on the maintenance responsibility (Table 2b). Decisions on sharing of responsibilities are agreed on in an international discussion and will be documented in the descriptors ‘responsibility’ and ‘restrictions’ within the ACCESSION table. This determines their status in the store of the genebank. Primary responsibility is taken over by a partner genebank for primary genetic resources (PGR), which may be most original samples (MOS) in the biological sense (Anonymous 2000a) or on behalf of political reasons (sovereign rights over national genetic resources). But primary responsibility defines itself not necessarily from biological or geographic criteria. It rather describes the duty of fulfilling certain standards of maintenance of and access to the germplasm, which includes holding a base and an available active sample of the accession as well as storing samples as safety duplicates at partner genebanks. Relevant for trusteeship in sharing of responsibilities are responsibilities on primary genetic resources (PGR) and safety duplicate samples (SDS)
697
Figure 1. A set of related tables concerning genotype and accession information enabling documentation of duplicate groups in original and compiled state
698 Table 2. Duplication and responsibility as basis for a differential storage management concept ¨ ¨ A) Duplication (van Hintum and Knupffer 1995; Knupffer et al. 1997) MOS IDD COD PAD CPD PRD
Most original sample Identical duplication: genetically identical (e.g. clones) Common duplicates: derived from the same original population Partial duplicates: selected from the same original population Compound duplication: one accession is a selection from the other Probable duplicate: duplication indicated by identical or similar passport data
¨ B) Responsibility (modified after Bucken and Frese (1999)) Responsibility Restriction
Storage Status
PGR REF SDS PEN REJ
Primary genetic resource Reference sample Safety duplicate sample of other institutions Pending responsibility Responsibility rejected
PUB RES EMB TOC EXE
Public Restricted Embargoed Temporary out of collection Lost or discarded
ACO BAS BAS NEW DAT
DMS PRO
Demonstration sample Project / working sample
PUB RES
Public Restricted
ACO
(Anonymous 2000b): Responsibilities of the maintainer of primary responsibility (PGR) are to 1. ensure that the accession is maintained under long-term conservation condition in compliance with the international standards and the quality standard procedures agreed within the crop network. 2. ensure that an appropriate safety duplicate is deposited in a genebank preferably within another country within the crop network. 3. provide unrestricted access to the accession to bona fide users from the crop network. 4. in case of impossibility to honour the commitment for long-term conservation and regeneration inform the database manager. Responsibilities of the maintainer of safety duplicates (SDS) are to 1. maintain a sufficient quantity of safety duplicated germplasm in long-term storage in compliance with the international standards 2. not distribute the germplasm and the related information 3. immediately notify the PGR maintainer in case of any problem with the safety duplicate 4. not carry out viability tests 5. not regenerate the safety duplicated germplasm
Active collection Base collection Base collection Newly acquired accession Sample lost or withdrawn, only information available Active collection
Genebanks are of course free to store any sample they wish to store, for example if a specific sample is frequently used and quick users’ access has to be guaranteed. Reference samples (REF), project or working (PRO) and demonstration samples (DMS) can be held even if from the global point of view they are superfluous as they belong to a duplicate group, for which a partner genebank has accepted primary responsibility. Reference samples (REF) may stay as duplicates in the base collection because they have been referenced in scientific publications or are considered valuable for other reasons, project samples (PRO) may be held as an active working collection for project purposes, demonstration samples (DMS) for public awareness raising projects. Decisions on responsibility for certain duplicate accessions may be pending (PEN). If a genebank rejects (REJ) the responsibility after consultation of partners, the accession can be returned to the original donor, reside inactive in the collection or can be discarded. Several restrictions may be laid on accessions of different responsibility type. Normally accessions belonging to a genebank’s primary responsibility have to be kept available and public (PUB). They belong to the active collection (ACO). Access to others may be restricted (RES) or even embargoed (EMB), especially if there is no primary responsibili-
699 ty of the holding genebank. There is no access to the safety duplicate collection which thus is also embargoed (EMB) and belongs to the base collection (BAS) of a genebank. Accessions may be temporarily out of an active collection (TOC) for technical reasons or if important information like taxonomy is unclear.
Gathering necessary information Knowing an accession’s history will facilitate determining its duplicate status and make decisions on sharing of responsibilities more rational. Unfortunately necessary information currently is only seldom found in the central crop databases so that most duplication can only be attributed to the PRD status. An accession’s history might be elucidated by strictly following a documentation scheme, especially in the central crop databases, which would enable to reconstruct the exchange pathway of accessions within the genebank network. The Multicrop Passport Descriptors suggest the fields institute code for the holding genebank (which might be more clearly named holder or holder code) and donor code for the donating institution with their respective accession identifiers (accession number and donor number).
Another important information, still missing in the MCP format are dates of receipt and introduction by the holder. Each tuple of holder code, accession number, donor code, donor number and respective dates forms an entry into the ACCESSION table, irrespective of seeds being still available. If no seed is available any more at an institution responsibility is set to REJ, restrictions to EXE and storage status to DAT. That way all information necessary to show the way of accessions through the institutions could reside in this table as is exemplified with a schematic form in Figure 2, of which the upper part shows information provided by GENOTYPE and related tables, while ACCESSION information is displayed within the lower part. The example is taken from the European Avena Database. Fischer’s Wirchenblatter III, a selection from an old landrace, is held at four institutions. In two cases it is known, which institution donated the accession to the respective holding institution. The sample held in Braunschweig (DEU001) seems to be a common duplicate of the Gatersleben (DEU146) sample. Thus by agreement between both German genebanks the BAZ Gene Bank rejected (REJ) the responsibility of maintaining an active sample and transferred the sample into the base collection (BAS). In the other cases missing information has to be requested.
Figure 2. Form showing accessions of a group of probable duplicates (identical cultivar name) in different genebanks (example from EADB). Further international discussion on sharing of responsibilities has to contribute the management data still lacking in this table.
700 Rationalization of the seed stock management ¨ Bucken and Frese (1999) introduced the concept of a differential and hierarchical storage management of established large-sized genebanks, which has tight connection to the discussion on sharing of responsibilities and its consequences for seed stock management in individual genebanks. Its paradigms have been presented as follows: 1. In most cases requests are the main reason for the decrease of viable seeds. 2. Most seed requests are unspecified. 3. The paradigm of ‘just in time delivery of germplasm’ availability has to be given up. 4. The paradigm of the ‘one to one philosophy’ of active to base collection has to be given up 5. Regarding regeneration of accessions a priority system has to be established. The main table for documentation of seed storage and management procedures in a genebank is called SEEDSTOCK in our system. It is designed to document data on that part of the seed stock, which is subject to dynamic management processes (germination tests, controlling the amount of viable seeds)
and describes the activity of samples (active and base samples) as well. This table is related to several other tables describing details of the seed stock management (germination testing, seed increase). A further table SAVESTORE describes a part of the base collection, which is not at all subject to dynamic management procedures and comprises safety duplicates of partner genebanks in the own storage as well as own safety duplicates at partner genebanks. There are only slight differences in the design of tables SEEDSTOCK and SAVESTORE. Nevertheless it makes sense not to burden the actively managed data in SEEDSTOCK with the merely passive data of SAVESTORE and keep both tables apart (Figure 3). Table 3 lists necessary seed samples and management procedures for accessions in regard to the responsibility status of the holding genebank. The attribute activity assigns samples in the seed stock to the active available (ACO) or the base collection (BAS). Active samples serve to satisfy user requests as long as the number of germinating seeds (calculated from the stored seed weight (storage weight), the TGW and the actual germinability) is higher than a certain threshold, which has to guarantee for successful regeneration from the remaining seeds. If
Figure 3. Tables for the seed stock management of individual genebank accessions
701 Table 3. Seed stock management in regard to the responsibility status of a genebank a) Necessary seed stock in regard of responsibility for a given accession Status of an accession in the genebank Necessary samples in genebank seed stock Documented in table ACCESSION field SEEDSTOCK.Activity table SAVESTORE Responsibility
Restriction
Storage Status
Active sample (ACO)
Base sample (BAS)
Safety duplicate sample (SDS)
PGR SDS REF REF /PRO DMS
PUB EMB EMB PUB /RES PUB
ACO BAS BAS ACO ACO
Yes No No Yes Yes
Yes No Yes No /(Yes) No
Yes (located at partner facilities) Yes (stored for partners in own facilities) No No No
Base sample (BAS)
Safety duplicate Sample (SDS)
LTS No Yes, every 10 years Yes
LTS No No Exchange on regeneration of the base sample
b) Management duties for the different parts of the seed stock Active sample (ACO) Storage conditions Available for seed exchange Germination monitoring Regeneration of seeds 1
STS 1 / LTS 2 Yes Yes Yes
STS: Short term storage conditions, 2 LTS: long term storage conditions, for details see Anonymous (1994)
parts of the active collection are currently not available the reason (mainly shortage of seeds) is documented as availability status. An important information regarding the biological status of the material is the number of regeneration cycles since the year of collection or acquisition of a sample. There is no detailed technical discussion on safety duplication procedures in Genebank Standards (Anonymous 1994). It is just mentioned that the base collection for a crop genepool or any species may be dispersed among several institutions. Frequently safety duplicates are handled as ‘black box’ in the receiving genebank. In BAZ Gene Bank outgoing as well as incoming safety duplicates have been documented accession wise to verify the transfer of all samples. The system provides the SAVESTORE table for both items. There is no seed stock management of safety duplicates in the holding genebank (duplication site). Thus this table should not be merged with the seed stock table, although several attributes are common in both tables (TGW, Germination, StorageWeight, GerminatingSeeds). In SAVESTORE they describe the seed lot sent to a partner institution. It is obvious from Table 3, that number of samples to be managed, management duties and resulting work load associated with a certain accession is greatly influenced by the responsibility status agreed
on. Considerable rationalisation of seed stock management could be achieved through identification of duplicates and subsequent reduction of the number of accessions in the active collection in order to minimise regeneration and seed viability monitoring work. Thus it is not recommended to completely eliminate duplicates from the base collections. They should be kept for disposal of future generations as embargoed reference samples in the base collection, where they cause only minimal management expenditures.
Potential for the rational collection building at the European level In Germany, the Netherlands and in the UK genebanks work close together with the national cultivar registration authorities to avoid any loss of the more recently developed germplasm. These authorities are obliged to keep reference seed samples for cultivars which are registered on a National List in the European Union, or for cultivars which are protected under national, EU or international legislation to allow comparisons with candidate cultivars for which protection is claimed. Within the framework of an informal agreement the German
702 Table 4. Examples for sharing of responsibilities for recently discussed obsolete cultivars
Federal Office of Plant Varieties (BSA 5 Bundessortenamt) routinely passes over the reference seed samples of cultivars that are no longer protected and have gone out of commerce. This agreement guarantees that germplasm no longer maintained by the breeder is safeguarded in genebank collections. A similar system is applied in the Netherlands. Every
five years ‘Naktuinbouw’ (Netherlands Inspection Service for Horticulture) formerly NAKG, responsible for the seed and planting material quality, provides the Dutch genebank with a list of cultivars which entered the national list or the EU list. Because the amount of varieties entering the list is very large and many varieties do not add to the
703 diversity already contained in the CGN collection a selection of these varieties has to be made. Genebank curators, variety breeders and plant breeder’s right advisers then discuss which of the accessions should be added to the genebank holding. The selection comprises national cultivars and cultivars from foreign countries as well (I. Boukema, CGN, personal communication). At the Scottish Agricultural Science Agency (SASA) safety duplicates of obsolete cultivars are kept. However, cultivar test centres neither have a clear formal responsibility for longterm genetic resources conservation nor the capacity to regenerate material when need arises. There are therefore good reasons to establish a transfer system between the national genebank and the cultivar registration authorities. Breeding companies are increasingly marketing their cultivars all over Europe and receive legal protection for the same cultivar in several countries. When the protection is extinct the same cultivar may be passed over to several national genebank holdings. To avoid unnecessary duplication and inflation of the European genetic resources collection it is essential that genebanks exchange information on germplasm transferred from the national testing centre to the national genebank. Genebank curators should jointly decide on the primary maintenance responsibility for these accessions. The acceptance of the primary maintenance responsibility does not imply that other genebanks are not allowed to keep a duplicate. It rather allows genebanks to prioritise their own work once a partner has accepted the maintenance responsibility. The presented attributes in the ACCESSION table can be used to document the agreements achieved by partner genebanks. Table 4 shows some examples. The first on barley shows the extent of duplication achieved with ‘Cytris’, a French cultivar obsolete since 1992. The other examples on lettuce, pea and rape have been recently discussed and brought to a decision by the BAZ Gene Bank and partner genebanks. The Dutch genebank decided not to include the lettuce obsolete cultivar ‘Stephanie’ into their holding. Hence the only sample of this cultivar is kept by the BAZ Gene Bank until an expert guided decision is taken in favour (responsibility 5 PGR) or against (REJ) the accession maintenance. The responsibility ‘PEN’ implies that the accession is neither put on the priority seed regeneration list nor is it shown on listings for users information. ‘Thirza’ and ‘Sugar
Lil’ are maintained in the Dutch and Scottish collection allowing the BAZ Gene Bank to reject maintenance responsibility. The maintenance responsibility for ‘Corvet’ is rejected by BAZ Gene Bank. This is a hybrid cultivar which cannot be regenerated by the genebank. It is kept at the HRI in Wellesbourne as a reference sample (REF). Though the variety as such is unique and could therefore be classified as primary genetic resource, it can be kept at the HRI only as a reference sample, because for the mentioned reason it cannot be regenerated and maintained according to genebank standards. Even if responsibility for an accession is rejected the information linked with the accession is kept as historical data. The data are not directly accessible as they are in the case of ACO samples but can be made available on request and can even be updated or extended if need arises.
Conclusion To deal with compilation of heterogeneous information on duplicate groups and the often highly hypothetical duplication status of accessions within a duplicate group it is suggested to set up different tables for information shared by all accessions in a duplicate group (genotype and origin information) and those specifically describing a genebank accession including original information provided by the holder of the accession. Accession information will deal also with the duplicate status in a biological sense and the outcome of negotiations on sharing of responsibilities on duplicate accessions (responsibility and restrictions), which determine the status of an accession in the collection of an individual genebank (storage status). According to the responsibility agreed on by a genebank up to three sample types (active sample, base sample, safety duplicate sample) have to be maintained for an accession in the seed store. Sharing of responsibilities aims in reducing work load especially in maintenance of active and security duplicate samples for duplicate accessions.
Acknowledgements The following colleagues provided information that enabled us to deal with the problem of sharing maintenance responsibility for obsolete cultivars in more detail: Dr. M. J. Ambrose, John Innes Centre,
704 Norwich; Ir. I.W. Boukema, Plant Research International - Centre for Genetic Resources, The Netherlands (CGN), Wageningen; and Dr. N. Green, Scottish Agricultural Science Agency, Edinburgh. We greatly appreciated their assistance and their comments on an earlier version of the manuscript which helped us to improve the paper in content and style. Further we thank our colleagues Dr. A. Diederichsen (PGRC, Saskatoon, Canada) and I.E. J. Koenig (INRA, Clermont-Ferrand, France) for valuable discussions on Avena, Mrs. M. Reddig and Mrs. A. Doelle, BAZ Gene Bank, for providing their long term experience with daily database work and the advisors of Genetic Resources and Crop Evolution for giving additional comments and valuable suggestions.
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