Seed Cleaning

84 Handbooks for Genebanks No. 8 Germplasm is most at risk from gene flow during regeneration (see Chapter 8) and controlling gene flow is essential to ensure genetic integrity. To reduce the risk in crops where transgenes are commonly part of new cultivars, it is recommended that regeneration be carried out in isolation from any areas where transgenic crops are likely to be grown. Information on crops’ transgenic status is essential to determine what measures, if any, are needed to confirm that germplasm is free of transgenes. It is recommended ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

that: • all results be made publicly available as soon as they have been confirmed; • all procedures and supporting information be presented; • the appropriate authority in the country of origin be informed in cases where transgenes are detected; and • for commercially released genetically modified crops and crops in experimental development, genebanks maintain a database of crops and their status in transgenic research. Once an accession has either been determined to not require testing or has tested negative, follow appropriate regeneration and maintenance procedures to maintain genetic integrity, as for all accessions. Procedures for testing for presence of GMOs The two basic methods to detect the presence of a gene/transgene are ELISA and PCR amplification. Both methods have already been described and are robust, although each has advantages and disadvantages. For example, ELISA detects the presence of a gene product (protein) and thus requires an expressing gene. Test kits are commercially available for most commercial events, which ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

can be used in the field. On the other hand, PCR can detect non-expressing gene sequences, in almost all tissues, but it is more difficult to perform and therefore not practical in the field. In most cases, the detection of a positive result using one method should be confirmed with a second method. If the materials are being analyzed at the molecular level for fingerprinting or diversity studies, an additional test for the presence of a transgene can be performed at minimal cost. The genes/transgenes that should be used in such tests include the current commercialized major events for the species. These can normally be found on the Internet and are indicated in the tests provided by commercial testing services (either as ELISA kits or PCR services). These will change as new transgenic events are introduced into the market or events become obsolete and are 85 Manual of ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

Seed Handling removed, although the need to test may continue for some time. The number of seeds in any accession may limit the level of detection. More information and technical guidance on sampling and detection of GMOs can be found at www.europa.eu.int/comm/environment/ biotechnology/pdf/recom2004_787.pdf. An updated list of validated methods is also available at http://biotech.jrc.it. Documentation Suggested descriptors to document accession-level information on the presence of transgenes include the following: • Source of the material for testing • Type of material (leaf, seedling, seed) • Number of plants sampled and tested per replicate • Number of ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

replicates • Transgenes tested • Method of testing • Date of test • Duration of test, if appropriate • Transgenes identified • Incidence of each transgene (%) 86 6. SEED PACKAGING AND STORAGE 6.1 Seed packaging What is meant by seed packaging? Seed packaging involves placing a counted or weighed sample of seeds into a container, which is then hermetically sealed for subsequent storage (see Flowchart 6.1). Why are seeds packaged? Seeds are packaged to: • prevent absorption of water from the atmosphere after drying; • keep accessions separate and avoid mixing them; and • prevent ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

contamination from insects and diseases. When should seeds be packaged? The best time to package seeds is immediately after moisture content has been determined to be within the required limits for safe storage.