Detection Methods Basics

Crops developed with the aid of modern biotechnology must meet a wide range of regulatory requirements before seed is sold to farmers to produce crops. Some regulatory bodies require provision of methods which detect the specific DNA or proteins associated with the biotech trait in the crop. These detection methods, which are typically the intellectual property of the trait developer(s), are often licensed by the trait developers to regulatory bodies, grain handlers, food companies, and other stakeholders for their use to ensure compliance with regulations or to segregate and preserve the identity of products. The CropLife International detection methods website provides an avenue for stakeholders to license these methods from the trait developer(s).

Precise and accurate detection methods are developed, validated and documented during the development of each new biotechnology-derived crop. They are integral to product development, quality control and regulatory data-gathering, and essential to supporting smooth and efficient global trade.

There are two primary types of detection methods in use today.

Types of Detection Methods

DNA-Based Methods

The most common technique for detecting a specific DNA sequence that comprises a given biotech product is the polymerase chain reaction (PCR). This technique can be qualitative to indicate the presence or absence of a sequence or quantitative to determine the amount of DNA from a biotechnology-derived crop present in a sample. “Event-specific PCR methods” are designed to detect DNA sequences unique to a specific biotechnology-derived product. Alternatively, methods that detect DNA sequences that are common to many events are referred to as “screening methods”.

PCR methods are extremely sensitive which allows for detection of small amounts of a biotech product present in a sample. However, because of this high level of sensitivity, these methods are susceptible to sample contamination, leading to “false positives” (i.e., the erroneous indication that a product is present in a sample) and thus, misleading results. As a result, these methods are best suited for laboratory use and cannot be reliably used at grain elevators or in the field.

Protein-Based Methods

Protein-based detection methods, commonly referred to as immunoassays, determine the presence or amount of a specific protein in plant tissues and derivative products. They require protein-specific antibodies and are often employed in the form of an enzyme-linked immunosorbent assay (ELISA) or lateral flow strips (also known as lateral flow devices).

Protein-based detection methods are robust and some are well-adapted for field use; they are often commercially available in kit format and are used extensively in the trade of commodities and seed purity testing.

Protein-based detection methods are unable to distinguish between different biotechnology-derived products that express the same protein. Further, since proteins are often denatured by processing, protein-based detection methods are most suitable for use on non- or minimally-processed materials (e.g., grain, flour). However, assays for use in specific processed materials have occasionally been developed.

Supporting smooth and efficient global trade

Different regions or countries have different approaches to the detection of biotechnology-derived crops and their products. These discrepancies can lead to variations in analytical results and disagreements between laboratories, which are likely to have a negative impact on trade.

CropLife International (CLI) believes that global harmonization of detection methods is necessary to ensure consistent testing and smooth and efficient global trade.

Thus CLI members work with international institutions and governments to ensure the introduction of transparent, workable standards that are harmonized where possible. Several government agencies, global standards organizations, and industry organizations, notably the International Organization for Standardization (ISO) and Codex, have been developing standards and guidelines for detection methods. These are published as International Standards and as Codex Guidelines.

In order to further promote harmonization, this database is provided to allow interested parties direct access to detection methods developed by CLI members.

References

Grothaus, G. D., Bandla, M., Currier, T., Giroux, R., Jenkins, G. R., Lipp, M., Shan, G., Stave, J. W., and Pantella, V. (2006) Immunoassay as an Analytical Tool in Agricultural Biotechnology. J. AOAC Int. 89:913-928.

Lipp, M., Shillito, R., Giroux, R., Spiegelhalter, F., Charlton, S., Pinero, D., and Song, P. (2005) Polymerase Chain Reaction Technology as Analytical Tool in Agricultural Biotechnology. J. AOAC Int. 88:136-155.

Lipton, C. R., Dautlick, J. X., Grothaus, G. D., Hunst, P. L., Magin, K. M., Mihaliak, C. A., Rubio, F. M., and Stave, J. W. (2000) Guidelines for the Validation and Use of Immunoassays for Determination of Introduced Proteins in Biotechnology Enhanced Crops and Derived Food Ingredients. Food Agric. Immunol. 12:153-164.