Finally an appropriate comparator should be chosen. This should ideally be a non-modified genotype of the LMO i.e. a (near-)isogenic line. This is used as a tool to distinguish between the effect of the novel genotype expressed by the LMO in the likely potential receiving environment as compared to how the organism would normally behave if it were introduced into the environment without the modification.

As seen above, a comparative approach is one of the general principles of risk assessment as set out in Annex III to the Protocol, where risks associated with the LMO “should be considered in the context of the risks posed by the non-modified recipients or parental organisms in the likely potential receiving environment”.

Using a comparator may help a risk assessor identify the novel characteristics of the LMO and assessing if the LMO presents a greater, lesser or equivalent risk compared to the non-modified recipient organism that is used in a similar way and in the same environment.

The ideal comparator is the closest non-modified genotype to the LMO, i.e. (near-)isogenic lines. Depending on the context, a risk assessor can also choose to consider similar or related non-modified genotypes as useful comparators. Related management practices and experience with similar non-modified organisms may also be helpful. For example, when considering the risk assessment for an insect resistant LM crop, a risk assessor may wish to consider, amongst other things, the available experience with pest control practices applied to non-modified organisms of the same species (e.g. use of spores from Bacillus thuringiensis as pesticides).

In some circumstances, choosing an appropriate comparator(s) could be a challenge. This may happen, for example, in the case of LM crops that are tolerant to abiotic stress if the non-modified recipient or parental organisms are not capable of growing in the receiving environment. In extreme situations, when a suitable comparator cannot be grown under the same conditions and in the same or similar receiving environment as the LMO, it may be necessary to treat the LMO as a novel species in that environment (i.e. introduced species). This means that the characterization of the LMO (see below) will focus not only in the novel genotypic and phenotypic characteristics resulting from the genetic modification, but rather on the characterization of an entire new genotype in the particular receiving environment.