Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

Shipman, David R.

English

Research Papers in Economics

1
"Testing for Biotechnology-Enhanced Grains and Oilseeds"
Remarks by David R. Shipman, Deputy Administrator, Grain Inspection, Packers and
Stockyards Administration, before the World Agricultural Outlook Forum, February 24,
2000.
Introduction
Having the ability to distinguish biotech crops, and even specific types of biotech crops
from conventional crops, is becoming more important for a variety of reasons.
q  Certain food manufacturers want to buy conventional crops separate from
biotech crops.
q  Some countries have announced regulations that will require the labeling of
biotech crops and products.
q  The country-by-country regulatory approval process has resulted in certain
varieties being approved in some countries but not in others.
q  Buyers and sellers will need to confirm the presence of enhanced value traits
in future generations of biotech crops if they want to benefit from the
enhanced value.
Regardless of the motives for segregating biotech from conventional or one quality trait
from another, verification testing will be necessary.  Unfortunately, testing for biotech
crops is substantially different from traditional grain quality testing.  The technology for
detecting biotech crops is rapidly evolving and quite variable at this time.  You either test
for the presence of the actual genetic material (DNA) inserted into the crop or you test for
the unique protein expressed by the inserted DNA.
Sampling
Regardless of the method used, a representative sample is essential.  As with most grain
quality tests, sampling is a significant source of variance.  The grain industry typically
relies on “systematic sampling” whereby a diverter-type (D/T) sampler diverts a small
slice of the grain stream on a pre-set time (e.g. 20 seconds).  The small slices are
combined to produce a sample representative of the entire lot (truck, railcar, barge, etc.).
That is, every kernel in the lot has a chance of ending up in the final sample.
Once the original sample is collected, a subsample is obtained using a divider, such as the
Borner divider.  This subsample must than be ground and mixed to ensure you have a
homogenous mixture.2
Types of Testing Available
Biotech crops differ from their conventional counterparts by the addition of one or more
new genes (DNA sequences) into the plant genome.  Each gene tells the plant to produce
a new protein that confers a new trait.  Biotech detection methods test either for the new
genetic sequences (the DNA) or the new proteins.  In general, separate tests must be
developed and optimized for each bioengineered variety.  While protocols can be
designed to test one product for the presence of several biotech traits, there are no
universal tests encompassing every biotech product.  In choosing the appropriate biotech
detection method, it is critical to understand the information needed; both DNA and
protein tests have suitable applications.
Conventional DNA
Specific DNA sequences in plant material can be detected using a technique called
polymerase chain reaction (PCR). PCR requires specific DNA sequence information,
which may be proprietary. The DNA is extracted from the ground sample. Then, primers
are used to select only the DNA unique to the inserted genes and then amplify or multiply
the unique sequence in a cyclic reaction.  In conventional PCR, these fragments of
multiplied DNA are than separated on an agarose gel. The size and intensity of the DNA
band(s) indicates the presence and relative level of targeted DNA within the sample. This
conventional PCR technique is very sensitive, and can detect <0.1% biotech material in a
sample (i.e, 1 bean in 1,000).
Let’s take a look at the performance of the conventional PCR testing in a controlled study
conducted by the European Union (“IUPAC Collaborative Trial Study of a Method to
Detect Genetically Modified Soy Beans and Maize in Dried Powder,” Lipp et al.,
published in the Journal of AOAC International, Volume 82, Number 4, 1999).  The
study used conventional PCR to detect the 35s promoter and the NOS terminator, 2
genetic elements important for the expression of the inserted genes and present in nearly
all biotech crops.  The study involved 29 laboratories in 13 countries.
Analysis of the 35S Promoter in Soybeans
No. of samples No. of samples Correctly
Classified
Correctly
Classified
% GMO Negative Positive Negative % Positive %
0.0 94 2 97.9 0
0.1 5 93 0 94.9
0.5 0 105 0 100
2.0 0 101 0 100
Overall 99 301 97.9 98.4
Source:  Lipp Et Al: Journal of AOAC International Vol. 82, No. 4, 19993
Analysis of the NOS Terminator in Soybeans
No. of samples No. of samples Correctly
Classified
Correctly
Classified
% GMO Negative Positive Negative % Positive %
0.0 96 0 100 0
0.1 7 91 0 92.8
0.5 3 102 0 97.1
2.0 0 101 0 100
Overall 106 294 100 96.7
Source:  Lipp Et Al: Journal of AOAC International Vol. 82, No. 4, 1999
Newer PCR technologies have increased the sensitivity and reliability of PCR
quantification beyond conventional methods.  The newest innovation is referred to as
real-time PCR.  One important feature of this new technology is that the DNA
amplification and analysis occur in the same reaction vessel, simplifying detection.
Amplification of target DNA is measured via fluorescence during the PCR reaction. This
versatile technology can produce accurate quantitative results as low as 0.01% biotech
material.  Real-time PCR is also more rapid (1 –2 days) than conventional PCR (2 – 3
days), significantly decreasing the time needed for confirmation of positive results.
PCR tests, however, have their limitations. PCR is susceptible to errors due to
contaminants, DNA breakdown, or improper implementation, and testing must be
performed under rigorous laboratory conditions with appropriate controls. Personnel
performing PCR assays must be highly skilled.  Equipment for PCR testing is also quite
costly, ranging from $20-30,000 for conventional PCR to $60-100,000 for real-time PCR.
For these reasons, PCR is not easily adaptable for rapid on-site testing at elevators or
processing plants.  Currently, PCR testing of crops and processed products for the
presence of biotech products is offered commercially at a cost of $200-450 per test; the
tests take 2-3 days to perform.
Protein Detection Methods
Proteins in GMO material may be detected using an ELISA (enzyme-linked
immunosorbent assay) test.  ELISA tests analyze for a specific antibody reaction that
marks the presence of the expected protein.  Two types of ELISA kits are available:
microwells and lateral flow or strip tests. Microwell kits are easy to use and can provide a
semi-quantitative determination of GMO content.  Results are obtained in 2-4 hours at a
cost of approximately $2-20 per test.  Lateral flow tests give qualitative (yes/no) results
for GMO material in less than 20 minutes, at a cost of $1-5 per test.4
The level of detection for these ELISA tests varies for each product tested (due to
differing levels of foreign protein in each product) and for each kit (due to the quality of
the antibody).  Current ELISA test kit manufacturers claim that the dipstick tests will
reliably detected 0.1% GMO for Roundup Ready soybeans and 2% GMO for Bt corn.
Caution must be exercised in interpreting ELISA test results, however.  Quantification is
difficult, as protein composition and expression levels for a given trait can vary widely.
One example is Bt insect resistance.  Three different Bt proteins are currently used in corn
varieties to confer resistance to the European Corn Borer: Cry1Ab, Cry1Ac, and Cry9c.
The amount of protein expressed by variety may differ and not all varieties incorporating
Cry1Ab, for example, produce the same levels of Bt protein.  One variety has been
specifically engineered to produce the Bt toxin only in the green leafy parts of the plant,
where the insects attack.  An ELISA test on the seed would yield a negative result.  PCR
testing would need to be performed to detect this particular genetic modification.  The
key to successfully employing an ELISA test, or any biotech crop detection method, is to
choose an appropriate application.
ELISAs are well suited for testing at the first point-of-sale, enabling verification of
identity on the spot by non-technical personnel. ELISAs are being marketed to seed
developers, elevators, and processors both in the U.S. and abroad.  Used as a risk
management tool in conjunction with a segregation system, ELISAs can be highly
effective when applied properly.  Likewise, PCR testing is valuable for confirmation of
sample identity and composition to facilitate final sale.  When performed by a credible
laboratory, PCR can be accurate, quantitative, and specific.
GIPSA’s Role
To improve the reliability of biotech testing and subsequently market confidence in
results, USDA through the Grain Inspection, Packers and Stockyards Administration
(GIPSA) has initiated steps to establish sampling protocols, and to evaluate and validate
the various testing methods being used in the commercial market.
As we speak today, we are holding a workshop in Kansas City, MO to review sampling
protocols and to review the PCR and ELISA testing methods used by government and
commercial laboratories.  We are also in the process of establishing a biotech reference
laboratory at the GIPSA Technical Center in Kansas City. The laboratory will have the
capability to verify PCR testing as well as ELISA and lateral flow tests. The ultimate goal
is to provide the market with reliable biotech detection methods that will facilitate
information exchange, and benefit American agriculture by increasing overall market
efficiency, decreasing transaction costs, and minimizing buyers’ and sellers’ risks.
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TESTING FOR BIOTECHNOLOGY-ENHANCED GRAINS AND OILSEEDS

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