GMO Testing Modality Comparison: On-Site QuickCombs and PCR Testing

The Relationship Between On-site GMO Combs & Laboratory PCR GMO Panels

GMO Testing Modality Comparison: On-Site QuickCombs and PCR Testing

photo of EnviroLogix’ 10-up GMO Corn
QuickComb for QuickScan in solution cup with carboard holder

EnviroLogix’ 10-up GMO Corn
QuickComb for QuickScan

One of the most frequent questions we get asked about our on-site GMO test for corn is why testing in corn requires a 10-up “comb” on inbound testing, but only a 4-assay PCR panel lab test to meet most common compliance standards.

EnviroLogix’ immunoassays detect GMO proteins in grain, whereas our PCR detects the GMO DNA. The table below shows the relationship between our corn comb (10 unique GMO Lateral Flow Device [LFD] strips connected with a bridge for easy handling) and the most commonly tested PCR panel.

Crop science laboratories are now routinely commercializing new traits on a regular basis. To keep your non-GMO operation compliant, EnviroLogix continually updates this table on our website, where you can also find a similar table for soy traits.

Table 1. Immunoassay GMO Trait Proteins and PCR GMO DNA Sequences

10-up Comb
Cry1 CP4 EPSPS Cry3 Cry1F PAT/pat Cry34 Cry2 mCry3A VIP eCry3.1Ab
Standard Panel
CaMV 35s MIR604 MIR162 GA21
photo showing PCR DNA test


If you’re interested in why this works for GMO testing, the answer gets very technical very quickly. The root comes down the biological basis of GMOs. Most modifications add DNA from one organism to a plant’s genome to allow that plant to express a new protein that creates a trait of interest.

For a plant to make a new protein, the added DNA includes both the sequence for the protein, as well as regulatory element sequence that “tells” the plant to turn that protein production on. Those regulatory sequences are often reused in many different GMO traits, which means that some GMOs might create different proteins but they have a common DNA sequence. The most common regulatory sequence used in GMOs and tested by PCR is CaMV 35s, which is a short piece of DNA from cauliflower mosaic virus.

PCR testing is complex and costly. To minimize the amount of testing needed, a CaMV 35s assay is commonly used to detect DNA from many different GMO traits at the same time. Conversely, these sequences cannot be tested by a common immunoassay strip; they are designed for quick screening and trait differentiation, which is why we continue to add more LFD strips to the comb over time.

Figure 1. Relationship between GMO Trait DNA and Expressed GMO Trait Protein
Diagram showing the relationship between GMO traits and GMO proteins from corn

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