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From October 12, 2001

Testing for GMOs in Crops

According to Ohio State University's Ag Answers, tests exist that measure levels of genetically modified material in crops. These tests can determine if crops of organic farmers and food producers have reached certain standards.

As concern for environmental and health impacts of GMOs grows, standards are being set that would require a very limited amount of genetically modified material to be present. One example is Japan's zero tolerance legislation for unapproved biotech material in seed and food imports. They also require that there be less than 5% GMO present in a product to be labeled a non-GMO. The European Union is considering a non-GMO label only for crops with less than 1% GMOs.

Food producers targeting markets such as these need to prove their crops meet the standards. There are several testing procedures that can accomplish this:

Herbicide bioassays test for herbicide resistant traits such as those present in Roundup Ready crops. Seeds are exposed to a particular herbicide. The seeds test positive for GMOs if they develop normally. If development is abnormal or the seed dies, the seed is GMO-free. This test is inexpensive but can take a week to get results.

ELISA (enzyme-linked immunosorbent assay) tests for presence of a protein within the plant that GMO DNA produces. This test is much quicker, taking between two to five minutes. Another test called PCR (polymerase chain reaction) determines exactly where the GMO is within the DNA sequence.