Viability of radish genetic resources
Contributors to this page: CAAS, China (Qiu Yang, Li Xixiang); Bioversity International, Italy (Imke Thormann, Ehsan Dulloo); CGN, Netherlands (Noortje Bas); IPK, Germany (Andreas Börner, Ulrike Lohwasser); AVRDC, Taiwan (Andreas Ebert); USDA, USA (Larry Robertson); NBPGR, India (Chitra Pandey); SASA, UK (George Campbell); University of Warwick, UK (Charlotte Allender).
Seed viability is most critical for seed distribution and an important criteria for regeneration during seed storage in the genebank.
- For smaller genebanks it can be cost-efficient to outsource germination tests to a certified local company, especially if they lack facilities, equipment and/or trained staff
- The viability should be determined before seeds are packaged and placed into the genebank storage rooms and at regular intervals during storage.
Type of test
- Standard germination test according to the Association of Seed Analysts (AOSA) 2005 and ISTA 2005 (it is the most accurate and reliable).
- Otherwise sequential germination test (it is less accurate, but requires less seeds and is suitable in case of limited number of seeds). This test should be undertaken twice for accuracy. If the results are below the critical value then an additional test should be carried out.
Number of seeds and replicates
- Standard germination test - 100 seeds and 2 replications (ISTA 2005, FAO/IPGRI 1994).
- 25-50 seeds and 2 replications, if the seeds are limited (ISTA 2005, FAO/IPGRI 1994).
- Seed moisture content shouldn’t be less than 8%.
- Sterilize the seeds using 1% solution of sodium hypochlorite for 10 minutes or hot water at 50 ºC for 20minutes and keep stirring, if fungal infections compromise a germination result CGN: does not sterilize seeds
- For wild types pre-cooling should be used.
- If the seed has been artificially dried before storage and the moisture content is below 8%, a period of equilibration of the seed before submission for routine germination test is recommended. The equilibrium period is achieved by allowing the seed to hydrate gradually to ambient conditions by simply leaving it on a cool laboratory bench out of direct sunlight for a few days before submitting for testing. This allows seed activity to resume and reduces any potential seed damage caused by a rapid change in moisture content.
- Petri dishes, filter papers and tap water.
- 25-28 ºC in a germinator incubator.
- No specific requirements.
Duration of test
- 10 days, up to a maximum of 28 days.
- Top-of-paper method
- Count the number of normal and abnormal seedlings after 4 days and 10 days (ISTA 2005).
- Additional 100 seeds should be tested with 2 replications if the germination is below 90%
- Repeat the germination test if the difference between the two replicates exceeds 10% or the maximum tolerance limit at 2.5% probability; or when judged necessary based on experience.
Documentation during viability testing
- Accession number
- Number of seeds tested per replicate and number of replicates
- Date of germination testing
- Days of first and final counts
- Number of germinated seeds at first count
- Germination % in replication 1 (%) at first and second count
- Germination % in replication 2 (%) at first and second count
- Final germination mean (% normal seedlings, second count)
- Germination retest (germination % of the re-tested sample)
- Abnormal germination %
- Dead seeds (%)
Routine monitoring methods are important to assure minimum quality (viability) and quantity of seeds in storage.
- Should be part of a routine inventory management of the active and base collection.
- A computerized stock control system should be developed to monitor the quality and quantity of seed accessions in cold store.
- Update documentation of seed stocks immediately, adjusting the total after all seed withdrawals.
Monitoring frequency of seed viability is adjusted to the genebank’s storage and use conditions of the active and base collection.
- Use FAO/IPGRI standards 1994, i.e. five years in active collection, ten years in base collection if storage conditions vary between the active and base collection and initial germination is not taken into account.
- Monitor every 10 – 20 years in either base or active collection, if storage condition of active collection is the same as base collection and if monitoring interval is calculated based on the initial germination percentage.
- For cultivated radish: 1000 - 1500 seeds.
- For wild relatives: 800 – 1000 seeds.
Critical germination level
- Cultivated radish: 80-85 % in base collection (IPK), 70% in active collection
- Radish wild relative: 60%, exceptions are acceptable in base collection; 50% in active collection.
Recording information during routine monitoring
The following information should be recorded for each monitoring step:
- Accession number (ID number)
- Any additional number identifying the accession
- Current % of germination
- Dates of monitoring % germination
- The current amount of seeds stored (grams or number).
- Number of regenerations
- Example for keeping track of regenerations: SASA retains the original accession number for each regenerated sample but qualifies it with an additional number which indicates how many generations the sample has been multiplied from the original- eg original seed is ‘accession number/0’, first generation seed is ‘accession number/1’ etc
References and further reading
Ellis RH, Hong TD, Roberts EH. 1985. Handbook of seed technology for genebanks. Volume 1. Principles and methodology. International Board for Plant Genetic Resources IBPGR, Rome, Italy.
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.
ISTA. 2005. International Rules for Seed Testing. Edition 2005. International Seed Testing Association, Bassersdorf, Switzerland.
Rao NK, Hanson J, Dulloo ME, Ghosh K, Nowel D, Larinde M. 2006. Manual of seed handling in genebanks. Handbooks for Genebanks No. 8. Bioversity International, Rome, Italy. Available in English (1.5 MB), Spanish (1.4 MB) and French (1.9 MB).