Seed Health Testing
The seed industry has a twofold responsibility in the area of seed health: to deliver sufficiently healthy seed to farmers and seed producers, and to respect international phytosanitary regulations.
Why is seed health important?
Seeds are the foundation to crop production and seed health is related to food production in various ways. Of particular concern to the seed industry is seed used for sowing. Seed-borne pathogens may cause disease or death of plants resulting in crop loss and thereby, food. In order to ascertain the health of commercial seed, seed health tests are required.
However, seed health tests differ from country to country and the results from one country may not be accepted in another. In order to approach the problem in a systematic fashion, seed companies decided to co-operate by exchanging information on seed-borne pathogens and developing test methods for their detection under the umbrella of the International Seed Health Initiative.
When seed health tests are applied, it is critical that they are performed in a proficient manner. In general, the principles of good laboratory practice must be followed at all times (see for instance http://ec.europa.eu/enterprise/pharmaceuticals/eudralex/vol-7/a/7ag4a.pdf).
Interpretation of the seed health test results
The seed industry recognizes that even when tests are carried out correctly according to the protocol, differences can exist due to the expression or condition of the pathogen. Tests can show identical results in cases where the pathogen is viable but a deviating result if the pathogen is dead or inactivated.
Many countries active in seed health testing make use of modern laboratory techniques. A PCR may be easier to implement by a developing country than a traditional direct method that requires skilled pathologists. Indirect tests (e.g. serological techniques and DNA/RNA based techniques) will detect both dead/non-infectious and viable/infectious pathogens in contrast to direct tests (grow-outs and bioassays) that give final proof of infestation by a viable pathogen.
Diagnostic methods for seed health testing should have the right balance between preventing infected seed lots from being sold (as a consequence of a false negative test result) and preventing unjustified measures such as discarding seed lots (as a consequence of a false positive test result). There are, however, considerations in using such indirect techniques and ISF has adopted a position paper that details them.