Site-directed nucleases: a paradigm shift in predictable, knowledge-based plant breeding

•SDNs deliver targeted mutations, gene modification, and DNA insertion.•SDNs may overcome constraints within conventional and transgenic plant breeding.•Some technical and regulatory issues may challenge the commercial use of SDNs.

Conventional plant breeding exploits existing genetic variability and introduces new variability by mutagenesis. This has proven highly successful in securing food supplies for an ever-growing human population. The use of genetically modified plants is a complementary approach but all plant breeding techniques have limitations. Here, we discuss how the recent evolution of targeted mutagenesis and DNA insertion techniques based on tailor-made site-directed nucleases (SDNs) provides opportunities to overcome such limitations. Plant breeding companies are exploiting SDNs to develop a new generation of crops with new and improved traits. Nevertheless, some technical limitations as well as significant uncertainties on the regulatory status of SDNs may challenge their use for commercial plant breeding.