hort communication of practical oriented research/information in agriculture or seed technology are presented in this section

Testing Seed and Grain for GMO Traits
A significant portion of North American maize, soybean, rapeseed and cotton production now comprises genetically modified varieties. The agriculture industry is suddenly faced with the need to determine the presence or absence of these traits in seed and in subsequently produced grain. The demand arises from both the seed and food industry to comply with certification and labeling requirements, respectively. In many cases, seed technologists have been given the responsibility of evaluating seed and grain for GMO traits. To the credit of seed laboratories, several approaches already are in place, including herbicide bioassays and Enzyme Linked Immunosorbant Assay (ELISA) tests.

Herbicide Bioassay Tests
Bioassays can be conducted with equipment common to most seed laboratories and are compatible with germination tests. They are conducted on 400 seed samples for seven days. Bioassays can be conducted in three ways: pre-substrate imbibition of seed, substrate imbibition of seed and seedling spray tests.

Pre-substrate imbibition tests are conducted where a sample of seed is soaked in herbicide solution for 16 to 24 hours. The sample is then rinsed and placed on the substrate for the germination test along with trait and non-trait check samples. When evaluating seedlings, the non-trait check sample should be used as a guide to determine whether the test seedlings contain the desired trait.

Substrate imbibition tests are conducted by placing the test sample directly onto substrate moistened with a herbicide solution. Normally, 400 seeds, along with five trait and five non-trait seeds, are allowed to imbibe for the seven days of the test. During evaluation the sample seedlings should be compared with the trait and non-trait check samples.

Seedling spray tests can be conducted on seedlings grown on germination substrate or grown under greenhouse conditions. The test seedlings and check samples are sprayed with the herbicide solution and allowed to grow for five to seven additional days. Seedlings are evaluated at 12 to 21 days of growth, depending on conditions and species.

ELISA Tests
The ELISA test is commonly used in laboratories to detect virus and bacteria, but it is a new technique for the majority of seed laboratories. The equipment required for an ELISA laboratory are quiet specific and include a plate reader (spectrophotometer), plate washer and multiple channel pipettes. ELISA tests are available for both insect and herbicide GMO traits.
        ELISA involves building a 'sandwich' containing a capture antibody, the specific trait protein, a detection antibody that is conjugated with an enzyme and a substrate specific for the conjugated enzyme. If the specific trait protein exists in the protein extract from the test material the amount can be quantified by observing the optical density of the color changes associated with the substrate enzyme interaction.
        ELISA tests can be conducted as lateral flow strips or in 96-well microtiter plates. In some cases, dry seed is crushed and assayed; in other cases, seedling leaf tissue is harvested and the protein is extracted. Source - Seed World Magazine, September 1999.  (NB: Seed World magazine can be contacted by e-mailing sweditor@sgcmail.com)
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