Re-evaluating the site-directed nuclease classification as a regulatory trigger for genome-edited plant products

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Re-evaluating the site-directed nuclease classification as a regulatory trigger for genome-edited plant products

Site-directed nuclease (SDN) classification into SDN-1, SDN-2 and SDN-3 outcomes is used for regulating genome-edited plant products in some countries. This reductive categorization system fails to cover the breadth of genome editing technologies developed over the past decade and their rapidly approaching commercial use. Here, we argue that, in the context of plant breeding, regulations should focus on the characteristics of the genome editing outcome, rather than specific methods used in the development process. Such a science-based, outcome-focused regulatory approach would future-proof the risk-proportionate oversight of plant breeding innovations and enable a more efficient delivery of improved crop varieties amidst growing concerns of climate change and evolving pests and diseases.

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Fig. 1: A case study example of different breeding methods reaching an identical outcome.

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Acknowledgements

We would like to acknowledge the support of the teams and leadership at BASF, CropLife International, Qi Biodesign, Bayer CropScience, Syngenta and Corteva Agriscience.

Author information

Authors and Affiliations

  1. BASF Australia Ltd, Melbourne, Victoria, Australia

    Osman Mewett

  2. CropLife International AISBL, Brussels, Belgium

    John McMurdy

  3. Bayer CropScience LP, Chesterfield, MO, USA

    Lieselot Bertho

  4. BASF Belgium Coordination Center, Ghent, Belgium

    Ana Atanassova

  5. Bayer CropScience Pty Ltd, Hawthorn, Victoria, Australia

    Naomi Stevens

  6. Syngenta Crop Protection LLC, Durham, NC, USA

    Scott Huber

  7. Corteva Agriscience, Johnston, IA, USA

    Maria Fedorova & Kevin Diehl

  8. Qi Biodesign, Beijing, China

    Kevin Tianmeng Zhao

Authors

  1. Osman Mewett
  2. John McMurdy
  3. Lieselot Bertho
  4. Ana Atanassova
  5. Naomi Stevens
  6. Scott Huber
  7. Maria Fedorova
  8. Kevin Diehl
  9. Kevin Tianmeng Zhao

Contributions

O.M., J.M. and K.T.Z. conceived and wrote the Comment. K.T.Z. prepared the figure. L.B., A.A., N.S., S.H., M.F. and K.D. edited and gave input to the Comment.

Corresponding authors

Correspondence to Osman Mewett, John McMurdy or Kevin Tianmeng Zhao.

Ethics declarations

Competing interests

O.M. and A.A. are employees of BASF. J.M. is an employee of CropLife International. L.B. and N.S. are employees of Bayer CropScience. S.H. is an employee of Syngenta. M.F. and K.D. are employees of Corteva Agriscience. K.T.Z. is a founder and employee of Qi Biodesign.

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Mewett, O., McMurdy, J., Bertho, L. et al. Re-evaluating the site-directed nuclease classification as a regulatory trigger for genome-edited plant products. Nat Biotechnol (2026). https://doi.org/10.1038/s41587-026-03028-0

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  • DOI: https://doi.org/10.1038/s41587-026-03028-0