Detection methods

The Basics

Precise and accurate detection methods are developed, validated, and documented to international standards during the development of each new genetically modified (GM) product. These methods are integral to product development, quality control and regulatory data-gathering, and are also essential to supporting efficient global trade and enforcing regional regulatory frameworks.

Some regulatory bodies require provision of detection methods which detect the specific DNA or proteins associated with the biotechnology-derived (biotech) trait unique to the GM product. Thus, detection methods are used to ensure compliance with regulations. They are also used to segregate and preserve the identity and purity of products. They are typically the intellectual property of the trait developer(s). Detection methods are often made available to stakeholders such as 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) to test for the presence of a GM product (Principles for the Transfer and Use of Intellectual Property).

1 Types of Detection Methods

There are two primary types of detection methods in common use today for GM products. For a more detailed discussion, refer to “Applications of Sampling and Detection Methods in Agricultural Plant Biotechnology” (Shillito and Shan, 2022).

1.1 DNA-Based Methods

Polymerase chain reaction (PCR) is the analytical technique most preferred to detect and/or quantify specific DNA sequence(s) present in GM product(s). PCR can be performed in a qualitative manner to detect the presence or absence of a sequence or quantitatively to determine the amount of target DNA present in a sample. “Event-specific PCR methods” are designed to detect DNA sequences unique to a specific GM product. Alternatively, “genetic element-specific methods” are designed to detect DNA sequences that may be common across several GM products.

PCR-based detection methods (PCR methods) are extremely sensitive, and thus able to detect small amounts of a biotech product present in a sample, typically 1 seed in 1000 or better. The PCR methods in the CropLife International Detection Methods Database are validated to meet internationally accepted performance requirements. Performance and validation of PCR methods is described in international standards (ISO 24276, Codex CXG74, ISO/DS 16393).  In addition, there are a large number of publications available describing in detail the needs and requirements for successful application of PCR methods.  Examples written by a group of authors from CropLife International member companies, grain traders and private testing laboratories can be found in Lipp et al. (2005) and Alarcon et al. (2019).

1.2 Protein-Based Methods

Protein-based detection methods (protein methods), such 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). Immunoassays 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 detection methods are often easy to use. LFDs, for example, are well-adapted for field use (Grothaus et al. 2006; Alarcon et al. 2019), are often commercially available in a kit format, and are used extensively in the trading of commodities.

Protein detection methods are unable to distinguish between different biotech products that express the same protein. Since proteins are often denatured by processing, protein 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).

2 Reference Materials

Reference Materials are used as standards in method calibration and if certified, must be produced according to international standards (Trapmann et al. 2017) and guidelines. CropLife International recognizes the need for reference materials for use in calibration and validation of detection methods, as well as in proficiency testing of laboratories.

Certified Reference Materials (CRMs) are commercially available globally for all commercial biotech crops developed by CropLife International members. These reference materials are offered for single events by each company through designated ISO-accredited CRM providers.

3 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 (4):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(1):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(2): 153-164.

Shillito R. and Shan G. (2022) Application of Sampling and Detection Methods in Agricultural Plant Biotechnology. Woodhead Publ. & Cereals & Grains Assoc. Bookstore. ISBN: 9780323992930

Stave J.W. (2002). Protein Immunoassay Methods for Detection of Biotech Crops: Applications, Limitations, and Practical Considerations, J AOAC Int. 85(3): 780–786.

Trapmann, S., Botha, A., Linsinger, T.P.J., Curtain, S.M., Emons, H. (2017) The new International Standard ISO 17034: general requirements for the competence of reference material producers. Accred Qual Assur 22: 381–387.

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