EPSO agrees with the general statement of EFSA that risk-assessments should be done in a case-by-case manner and that the suggested procedures for risk assessment of SDN-3 that pertain to risk assessments of transgenes do not apply to SDN-1, SDN-2 and oligonucleotide-directed mutagenesis, and should be simplified for these. Furthermore, EPSO suggests clarifications in the definitions of SDN-1 and SDN-2 and the nature of the introduced base changes using these two techniques.

 The EFSA public consultation of the applicability of site-directed nucleases type 3 safety assessments on plants developed using site-directed nucleases type 1, type 2, and oligonucleotide-directed mutagenesis.

 EFSA has issued in 2012 a scientific opinion on the safety assessments of plants developed using Site-Directed Nucleases type 3, SDN-3 (EFSA, 2012). In these plants, site-directed nucleases have been used to introduce exogenous (recombinant) DNA in a site-specific manner through homologous recombination.

In spring 2020, EFSA issued a draft scientific opinion for public consultation on the applicability of the safety assessments of type 3 site-directed nucleases (SDN-3) on plants developed using SDN-1 SDN-2, or oligonucleotide-directed mutagenesis (EFSA 2020). In plants developed using either of these techniques, no exogenous (recombinant) DNA is inserted into the plants. In SDN-1, predominantly point mutations or short in/dels are introduced through non-homologous end-joining at the target cleavage site. In SDN-2 and oligonucleotide-directed mutagenesis, a short nucleotide sequence is used to guide the inherent DNA-repair mechanism to introduce a few predetermined base changes. Mainly EFSA promotes a case-by-case risk evaluation and outlines possible simplifications concerning specific genome editing methods. If no exogenous (recombinant) DNA is inserted into the plant, the subset of SDN-3 risk assessment protocols that evaluates transgenes are not applicable.

Click here to read: Full EPSO statement 24.6.2020, EPSO submission to EFSA, 28.5.2020


  • Jens Sundstrom, SLU Uppsala, SE & EPSO
  • Peter Rogowsky, INRAE, FR & EPSO AgT WG chair
  • Karin Metzlaff, EPSO, BE