Storage in seed banks for forage grass genetic resources

Contributors to this page: ILRI, Addis Ababa, Ethiopia (Jean Hanson); Bioversity International/ILRI, Addis Ababa, Ethiopia (Alexandra Jorge).

Contents: Base collection Active collection Storage management

 

Base collection

When it should be used

• All original samples should be placed in long-term storage (original samples are the best representative sample of that accession and storage conditions should be used to retain viability for as long as possible).
• In addition, representative samples of all accessions should be stored in base collections for long-term storage.

Sample specifications

Minimum sample size/viability for storage:

• 4000 seeds or 5 g for small seeds of 90% germination or 80% germination for wild species (see FAO/IPGRI, 1994).

Moisture content

• 3-7% (according to FAO/IPGRI, 1994).

Container specifications

Seed packaging method

• Laminated re-sealable aluminium foil packets are moisture proof and very practical, making good use of space.
• Use of vacuum for packing is optional.
• Packing is best carried out in an air-conditioned room with controlled humidity as soon as possible after drying (rapid packing in a dry environment prevents reabsorption of moisture by the seeds during packing).

Specifications of packaging material

Minimum quality: outer polyester of 12 µm thickness, middle aluminium layer of 9 µm thickness and inner polythene layer of 55 µm (this thickness is impermeable, sufficiently flexible for handling and strong enough for forage grass seeds, which are usually smooth).

Storage specifications

The two commonly available options for seed storage are walk-in cold stores and freezers. The choice depends on the number of accessions to be stored, seed size and storage temperatures selected.

• When collections are small and sub-zero temperatures are required, chest or upright freezers are a cheaper option for seed storage.

Assigning location codes

• Location codes should specify the exact place in the store (e.g. unit/block number, row number, shelf number and tray/box number) or freezer (e.g.  freezer shelf and box number). The exact locations are very important to locate material in the store.
• Moveable shelves on tracks are preferred (moveable shelves make best use of space).

Storage conditions

• At -18^oC to -20^oC (FAO/IPGRI, 1994).

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Active collection

When it should be used

To store seeds for distribution and use (seed quantities for distribution are usually larger and are not usually stored for long periods, therefore storage conditions are less stringent).

Sample specifications

Minimum sample size/viability for storage:

• A minimum of 1500 seeds and up to 500 g and above 80% of original germination (sufficient seeds for distribution needs for period of high viability).

Moisture content:

• 3-7% (according to FAO/IPGRI, 1994).

Container specifications

Seed packaging method

• Laminated re-sealable aluminium foil packets are moisture proof and very practical, making good use of space.

• Plastic or metal containers if store is dehumidified (store must be dehumidified to avoid absorption of moisture from the air surrounding the seeds).

Specifications of packaging material

• Laminated aluminium foil: minimum quality: outer polyester of 12 µm thickness, middle aluminium layer of 9 µm thickness and inner polythene layer of 55 µm (this thickness is impermeable and sufficiently flexible for handling and strong enough for forage grass seeds, which are usually smooth).
• Plastic or metal containers: Square-based bottles with a screw cap and inner rubber seal made of pure plastic materials (high quality), semi transparent, white in colour, adequate volume or metal cans of similar design.

Storage specifications

Assigning location codes

• Location codes should specify the exact location in the store, e.g. unit/block number, row number, shelf number and tray/box number (exact locations are important to locate and access material in the store).
• Moveable shelves on tracks are preferred (moveable shelves make best use of space).

Storage conditions:

• Between 0 to 10^oC (conditions to maintain seed viability for at least 25 years).

For information on safety duplication, click here.

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Storage management

Storage space arrangement

• Moveable racks (this maximizes space between and on the racks in the store and is the most economic way to utilize the space).
• Shelves should be spaced slightly more than the height of the containers.

System for tracking material/inventory system

• Database of stock and location and use of barcodes (databases are needed to keep track of information. Barcodes help avoid errors in recording).

Recording information during conservation

The following information must be recorded for each accession:

• Accession number (ID number).
• Lot number (ID number).
• Weight of seeds (weight of seeds in store).
• Number of seeds (number of seeds in store).
• Thousand or hundred seed weight (weight of 1,000 or 100 seeds).
• Number of packets (number of containers for seeds of one lot of one accession).
• Location of containers (store, shelf or box number).
• Type of container (material and size of container).
• Year of production of seeds (indicates age of seeds).
• Flag for regeneration (Y/N).
• Flag indicating seed availability and distribution status (A, L, S).
• Year of safety duplication (year).
• Institute holding the duplicate (name of institute holding the safety duplication).
• Location of duplicate sample (box label where the duplicate sample is placed).

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References and further reading

Chin HF, Hanson J. 1999. Seed storage. In: Loch DS, Ferguson J, editors. Forage Seed Production Vol. II Tropical and Subtropical Species. CABI, Wallingford, UK. pp. 303-315.

FAO/IPGRI. 1994. Genebank standards. Food and Agriculture Organization of the United Nations, Rome and International Plant Genetic Resources Institute, Rome. Available in English, Spanish, French and Arabic.

Harty RL, Hopkinson JM, English BH, Alder J. 1983. Germination, dormancy and longevity in stored seeds of Panicum maximum. Seed Science and Technology 11:341-351.

Whiteman PC, Mendra K. 1982. Effects of storage and seed treatments on germination of Brachiaria decumbens. Seed Science and Technology 10:233-242.