A novel in vivo genome editing doubled haploid system for Zea mays L.

Doubled haploid (DH) technologies accelerate maize inbred development. Recently, methods using CRISPR-Cas have created gene-edited maize DH populations, albeit with relatively low editing frequencies. Restoring fertility via haploid chromosome doubling remains a critically important production constraint. Thus, improved editing and chromosome doubling outcomes are needed. Here we obtained maternally derived diploid embryos in vivo by ectopically co-expressing Zea mays BABY BOOM and cyclin D-like gene products within unfertilized egg cells. When combined with gene editing, the in vivo method enables the production of mature seed with a maternally derived, gene-edited diploid embryo without requiring in vitro tissue culture methods nor the use of a chemical chromosome doubling agent. In summary, we report a novel approach for creating gene-edited maize DH populations that we expect can accelerate genetic gain in a scalable, cost-effective manner.