Cauliflower Mosaic Virus

Genes that encode proteins (traits) need genetic elements called promotors in order to initiate the expression processes.

Cauliflower Mosaic VirusA very effective promotor is known as 35S. This promotor is derived from a common plant virus, the cauliflower mosaic virus. It is common practice in DNA-based analysis to detect the 35S promotor instead of the encoding gene as many different genetic modifications use the same promotor.
The problem is that unmodified plants can be infected by the actual cauliflower mosaic virus. Such plants would be GMO-positive in a DNA-based analysis without ever having been transgenic. Cauliflower mosaic virus (CaMV) infections are widespread among cruciferous plants, including canola. To be sure, screen for CaMV in the DNA analysis.

Source: Brunt et al. (1997): Plant Viruses Online: Descriptions and Lists from the VIDE Database. Retrieved from