Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Oral Communication Abstract

GMO DETECTION: APPLICATIONS ON TRACEABILITY, A CRITICAL REVIEW

GIOVANNINI T.

Cerestar SpA, Molecular Biotech. R & D Center, Massa Lombarda, Ravenna

tgiovannini@eridania.it

GMO, traceability, PCR

The need to verify GMO levels in foods has created new demand for analytical testing, not only in countries where GMO labelling requirement is compulsory, but also in those that want to export food products into countries with restrictions.

There are two common approaches to GMO detection: Polymerase Chain Reaction (PCR)–based methods, which detect genetically modified DNA sequences, and Immuno Assays (e.g. ELISA), which detect and measure levels of proteins expressed by transgenic genes. Official standard tests, yet to come, will be based on these two methodologies. PCR-based tests are now preferred for the sensitiveness and the capability to detect a wider range of constructs. Protein-based immuno assays tests are quicker and require less lab skills.

For PCR-based methods target sequences can be the specific genes introduced (e.g. the Bt gene, the herbicide resistance gene, etc.), a regulatory sequence (e.g. promoter and terminator), a sequence spanning between a regulatory sequence and a gene or, better, a sequence between the gene and the flanking genome. Marker genes are associated to the heterologous genes of interest. Sometimes they are semi-silent (e.g. ampicillin resistance) but their sequence is still in the plant genome and therefore identifiable.

Collaborative study results put in evidence that PCR tests are generally good for detecting the presence of GMOs on a qualitative basis (yes/no). Difficulties arise when GMOs have to be quantitatively identified in food ingredients. Real time, or kinetic PCR, points out quantification and interpretation limits when quantification has to be done on a very small total DNA amount.

A general drawback for the PCR-based technique is the challenge to know which GMO-specific DNA sequence to target. Many labs find it difficult to keep up with the rate at which life science companies are creating new GMOs and the finding of adequate reference standards to be used as positive analytical controls.