Are there tests to identify if
my grain has been genetically modified?
With the hype this marketing year concerning the segregation of GM and non-GM grain, farmers are asking "Can anyone really tell if my grain has been genetically modified or not?" Obviously, the need for accurate testing and verification of grain samples has increased. There are two types of testing available:
Immunoassay – This test uses antibodies which react with specific proteins, such as the Bt protein in corn or Roundup Ready protein in soybeans. There is no accurate immunoassay at this time for Roundup Ready corn. The test is similar in technology to the home pregnancy test. If the rabbit dies, it must be Bt. This test can be conducted at the elevator but laboratories with better facilities and trained staff can run the tests more precisely. At the elevator facility, a representative sample of about 1000 kernels of corn or soybeans is ground and divided into two test tubes along with a solution. Most labs use three test tubes of 333 kernels per sample for more accuracy. A specially treated membrane strip is placed into the solution and if it changes color within a few minutes, the protein you are testing for is present. Each membrane strip is for a specific protein. Bt test strips will not work for Roundup soybeans and vice versa.
This sounds great but some precautions should be taken.
- The sample must be representative of the entire load.
- The test can find one GM grain out of a sample of 500 but not one out of 1000.
- The person reading the test should be thoroughly trained. The color changes on the membrane can be slight.
- Labs have machines called "plate readers" which measure optical density. This machine can quantify the percentage of GM grain in a sample. Few if any elevators have this machine.
Polymerase chain reaction (PCR) – This test is conducted only in laboratories and searches for the specific Bt or Roundup gene protein expressed by DNA and for the actual DNA. Unlike the strip test, the PCR test can detect the Roundup Ready gene in corn. .
Some key points about the PCR test are:
- Even though this is a very precise test for the presence of DNA, it’s imperative that the sample being analyzed is representative of the entire load.
- One GM grain out of 5,000 can be found from the sample.
- It takes at least five days to run this test.
- A single test can run between $400-$450.
- The PCR test cannot analyze what percentage of GM is in the sample, only its presence or absence.
To successfully market approved GMs such as YieldGard Bt and Roundup Ready soybeans, verification tests such as these need to be competently utilized. Until the world fully understands GM grain is completely safe, tests like these will be standard procedures for marketing identity preserved non-GM grain. |
