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Viability of maize genetic resources

Contributors to this page: CIMMYT, Mexico (Suketoshi Taba, Bonnie J Furman), with inputs also received from IITA, Nigeria (Dominique Dumet), EMBRAPA (maize and sorghum genebank), Brazil (Flavia Teixeira), USDA (ARS/NC7, ISU), USA (Mark Millard).

Contents:
Viability testing
Routine monitoring

Viability testing

Seed viability (percent of germination) of accessions is the most critical factor for seed distribution from the genebank and for new cycles of regeneration. The initial germination test of seed lots of new introductions or seed increased in nurseries is conducted after the seed is dried to the optimal moisture content (6-8%). Once in storage, the first monitoring of seed viability is conducted after ten years of storage in the active collection; then, after every five years as recommended by the standard germplasm bank operation guidelines (FAO/IPGRI 1994).

Laboratory methods

Preparing germination tests using a counting board on
wet filter paper (photo: CIMMYT)

The wet paper with the seeds is rolled and placed
in germinating trays (photo: CIMMYT)

The determination of germination percent (%) should be performed with seeds that are dried and cleaned. It is recommended to follow the ISTA rule to count the seeds that have normal and abnormal germination after four and seven days to determine the percent of germination.

Type of test

Number of seeds and replicates

Pre-treatment

Media

Temperature

Light

Duration of test

Other

Recording information during viability testing

The following information should be recorded for each testing step:

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Routine monitoring

This routine checks are very important to maintain the genebank operation in perpetuity. The seed accessions should be constantly available to the users.

Methods

Monitoring intervals

Routine monitoring is necessary to ensure viability of seed accessions in both the base and active collections. It is important that seeds be constantly available to users.

Critical germination level

Seed viability is necessary to ensure a sufficient sample size of accessions for the maintenance of genetic integrity over many regeneration cycles. Seed viability is critical to avoid a population bottle neck of accessions during storage.

Recording information during storage monitoring

References and further reading

Berthaud J, Savidan Y, Barré M, Leblanc O. 1997. Tripsacum. In: Fuccillo D, Sears L, Stapleton P, editors. Biodiversity in Trust. Cambridge Univ. press.

Ellis RH, Hong TD, Roberts EH. 1985. Handbook of seed technology for genebanks volume I. Principles and Methodology. Handbooks for Genebanks no. 2. International Board for Plant Genetic Resources, Rome. http://www.bioversityinternational.org/index.php?id=19&user_bioversitypublications_pi1[showUid]=2405.

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.

Hanson J. 1985. Procedures for handling seeds in genebanks. Practical manuals for genebanks no. 1. International Board for Plant Genetic Resources, Rome. HTML version available from: http://www2.bioversityinternational.org/publications/Web_version/188/.

International Seed Testing Association ISTA. 1993. International rules for seed testing. Seed Science and Technology 21, Supplement.

Justice OL, Bass LN. 1978. Principles and practices of seed storage. Agriculture handbook no. 506. U.S. Government Printing Office, Washington D.C.

Taba S, van Ginkel M, Hoisington D, Poland D. 2004. Wellhausen-Anderson Plant Genetic Resources Center: Operations Manual, 2004. El Batan, Mexico: CIMMYT. Available here.

Taba S. 1997. Teosinte. In: Fuccillo D, Sears L, Stapleton P, editors. Biodiversity in Trust. Cambridge Univ. press. pp 234-242.

Walters C, Wheeler LM, Grotenhuis JM. 2005. Longevity of seeds stored in a genebank: species characteristics. Seed Science Research 15:1-20.

Warham EJ, Butler LD, Sutton BC. 1996. Seed testing of maize and wheat: A laboratory guide. CIMMYT, Mexico and CAB International, UK.

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The Genebanks

The 11 CGIAR genebanks currently conserve 730,000 of cereals and grain legumes, forage crops, tree species, root and tuber crops, bananas and crop wild relatives.

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