Authors: Padmavati G. Gore and Kuldeep Tripathi
Plant genetic resources are the genetic material of actual or potential value. PGR is key to successful crop improvement. Enormous diversity of plants is present in nature, to secure our future we are trying to conserving it by exploring natural habitats of plants. Collection of plant from natural habitats and conserving them outside of their traditional environment is called as ex- situ conservation. Presently Genebanks around the world hold large number of germplasm of crop plants for long-term conservation for ease of access by plant breeders, researchers and other users. With advancement of technologies collection and conservation has been immensely increased but, with this many germplasm collections now face major problems of size and organization. Large number of collections hindering the use of genetic diversity they hold. In this situation core collection has to play a major role.
Core Collection Need
Genebank is undertakes lots of activities viz., collection of germplasm and then conservation, regeneration, duplication, documentation, evaluation and its use. Large number of accessions are hinders the activities of genebank. It is difficult to decide what the priorities are, whether gaps exist or when new material should be added to the collection. Thus the large size of the collection makes users unaware of variation in the collection; variation that might perform well in their environments, or benefit their breeding programmes, or enrich their research projects. To resolve all this issues Frankel (1984) proposed that a limited or “core collection” could be established from an existing collection. A core collection provides a structured sample from the collection; one that is a more manageable size than the whole collection. Its structure is such as to represent the diversity of the collection. It forms a reference set, and, when choices have to be made, an automatic priority for attention. It does not replace the existing collection or material from which it is obtained.
What is a core collection?
A core collection is a limited set of accessions representing, with a minimum of repetitiveness, the genetic diversity of a crop species and its wild relatives (Frankel 1984). From this definition, two operational definitions have followed: For an individual genebank, a core collection consists of a limited number of the accessions in an existing collection, chosen to represent the genetic spectrum in the whole collection. It should include as much as possible of its genetic diversity (Brown 1995). Such a set of a set of accessions has also been called a “core subset” of the whole collection. For a whole crop species, a core collection consists of a limited number of entries chosen to represent the genetic diversity of the whole crop species and its wild relatives. It is a synthetic and comprehensive core collection, assembled cooperatively by national and international genebanks and supplemented with fresh samples of wild or crop populations where needed to fill gaps. A core collection will always be substantially smaller than the collection from which it is formed. Brown (1989) suggested that it should be no more than 10% of the whole collection and always less than 2000 entries. In practice, most core collections are between 5% and 20% of the collections from which they were established.
Procedure of the development of core:
Collection in hand
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Passport and characterization data (geographic, genetic, agronomic)
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Groups of accessions
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Choice of entries for core
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Core set
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Evaluation
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Direct use
Function of core collection:
| Task | Function of core Collection |
| Dealing with new accessions | Provide a reference set for determining the group of accessions with which new material should be compared |
| Detection of gaps or uneven | Allow identification of discontinuities in collecting variation indicating missing material or sets where large amounts of variation are associated with a few accessions Collection management |
| Developing regeneration | Core entries have priority, especially schedules when upgrading collections |
| Prioritizing handling | Provide set for priority handling when needed |
| Monitoring viability | Provide appropriate set of accessions for monitoring whole |
| Duplication | Act as a priority group for safety duplication, for further distribution to regional or international genebanks or for maintenance in different conditions (e.g. as DNA libraries, in field banks or in vitro) |
| Development and application of new conservation methods | Provide test material of choice for possible improved maintenance procedures (e.g. ultra-dry seeds, in vitro and cryopreservation) Information management |
| Database organization | Provide benchmark standard for documentation and allow stratification of whole collection to be recorded Study and use of collections |
| Developing descriptor lists | Entries appropriate to test sufficiency of descriptors to discriminate accessions |
| Genetic studies | Allow selection of optimal material for studies of trait inheritance and estimation of general combining ability |
| Prebreeding | Provide dissimilar groups likely to assist in identifying heterosis or bringing together new gene combinations |
About Author / Additional Info:
Currently working as scientist in ICAR-NBPGR.