Detection of herbicide resistance genes in GM crops and assessment of cross-contamination between sample processing using mechanical shear homogenization

Genetically Modified (GM) crops allow for the introduction of new traits, such as resistance to pests, disease, and herbicide. The introduction of these genetic elements tends to confer advantages including crop hardiness or yields, which in turn can benefit farmers. In this application note, we assessed the efficiency of DNA isolation from either organic soybeans or soy powder samples from GM soy. Extracted DNA was subjected to PCR and fragment analysis by gel electrophoresis to identify the genetically-modified EPSPS gene.

We also assessed the degree of carry-over observed in a PCR-based assay when using a stainless-steel probe subjected to only disassembly and thorough rinsing between samples rather than full cleaning and autoclaving. The Omni GLH 850 rotor-stator homogenizer was efficient in extracting DNA from both matrices, with resulting DNA yielding clean PCR products as observed on the gel. Use of the single-use Omni Tip disposable plastic probes resulted in no detection of the resistance gene from organic soy, as expected; however, samples processed using the stainless-steel generator probe resulted in visible PCR fragments from not only the GM soy powder but also the organic soybeans. Our results indicate that disassembly and rinsing of the probe is likely insufficient to prevent cross-contamination between samples for PCR-based assays. As resulting DNA yields were more than sufficient for multiple rounds of PCR, if needed, the Omni GLH 850 rotor-stator homogenizer combined with the single-use plastic disposable probe is the recommended combination for research assays sensitive to low-levels of analyte.

For research use only. Not for use in diagnostic procedures.