Detection Methods Basics

GM crops are required to meet a wide range of regulatory requirements before seed is sold to farmers. Precise and accurate detection methods are developed, validated, and documented during the development of each new GM crop. These methods are integral to product development, quality control and regulatory data-gathering, and are also essential to supporting efficient global trade.

Some regulatory bodies require provision of detection methods which detect the specific DNA or proteins associated with the biotech trait in the crop. These methods are used to ensure compliance with regulations or to segregate and preserve the identity of products and are typically the intellectual property of the trait developer(s). They are often provided to regulatory bodies, and made available to seed producers, grain handlers, food companies, and other stakeholders via licenses or third-party testing laboratories.

The CropLife International Detection Methods website provides an avenue for stakeholders to license these methods from the trait developer(s).

Types of Detection Methods

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

DNA-Based Methods

The most common technique for detecting a specific DNA sequence that comprises a given biotechnology product is the polymerase chain reaction (PCR). This technique can be performed in a qualitative manner to indicate the presence or absence of a sequence or quantitatively 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, screening methods detecting DNA sequences that are common across biotech crops are referred to as “genetic element specific methods”.

PCR methods are extremely sensitive, which allows for detection of small amounts of a biotechnology product present in a sample. The PCR detection methods in this database are validated for expected performance requirements. Performance and validation of PCR methods is described in international standards (ISO 24276, Codex CXG74).  In addition, there are a large number of publications available describing in detail the needs and requirements for successful application of PCR-based detection methods.  Examples written by a group of authors from CLI member companies, grain traders and private testing laboratories can be found in Lipp et al. (2005)  and Alarcon et al. (2019).

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 (Lipton et al. 2000; Alarcon et al. 2019). 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 (LFDs)).

Protein-based detection methods are often easy to use with LFDs being well-adapted for field use (Grothaus et al. 2006); they are often commercially available in kit format and are used extensively in the trade of commodities.

Protein-based detection methods are unable to distinguish between different biotechnology-derived products that express the same protein. Furthermore, since proteins are often denatured by processing, protein-based detection methods are most suitable for use on unprocessed or minimally processed materials (e.g., seed, plant tissues, grain, flour). However, assays for use in specific processed materials have occasionally been developed (Stave 2002).

Reference Materials

Reference Materials are used as standards in method calibration and if certified, must be produced according to international standards and guidelines. CropLife International recognizes the need for materials for use in calibration and validation of detection methods, as well as proficiency testing of laboratories. CropLife International members produce certified reference materials via third parties operating under ISO standards.

Certified Reference Materials are globally, commercially available for all commercial biotech crops developed by CropLife International members. These reference materials are offered for single events by each company through designated ISO-certified third-party sources.

References

Alarcon, C. M., Shan, G., Layton D.T, Bell, T.A., Whipkey, S., Shillito, R.D. (2019). “Application of DNA- and Protein-Based Detection Methods in Agricultural Biotechnology.” J Agric Food Chem 67(4): 1019-1028.

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.

Stave J.W., (2002) Protein Immunoassay Methods for Detection of Biotech Crops: Applications, Limitations, and Practical Considerations, Journal of AOAC INTERNATIONAL, 85: 780–786. https://doi.org/10.1093/jaoac/85.3.780