CRISPR/Cas9‐mediated targeted mutagenesis of GmFT2a delays flowering time in soya bean

Summary Flowering is an indication of the transition from vegetative growth to reproductive growth and has considerable effects on the life cycle of soya bean ( Glycine max ). In this study, we employed the CRISPR /Cas9 system to specifically induce targeted mutagenesis of Gm FT 2a , an integrator in the photoperiod flowering pathway in soya bean. The soya bean cultivar Jack was transformed with three sg RNA /Cas9 vectors targeting different sites of endogenous Gm FT 2a via Agrobacterium tumefaciens ‐mediated transformation. Site‐directed mutations were observed at all targeted sites by DNA sequencing analysis. T1‐generation soya bean plants homozygous for null alleles of Gm FT 2a frameshift mutated by a 1‐bp insertion or short deletion exhibited late flowering under natural conditions (summer) in Beijing, China (N39°58′, E116°20′). We also found that the targeted mutagenesis was stably heritable in the following T2 generation, and the homozygous Gm FT 2a mutants exhibited late flowering under both long‐day and short‐day conditions. We identified some ‘transgene‐clean’ soya bean plants that were homozygous for null alleles of endogenous Gm FT 2a and without any transgenic element from the T1 and T2 generations. These ‘transgene‐clean’ mutants of Gm FT 2a may provide materials for more in‐depth research of Gm FT 2a functions and the molecular mechanism of photoperiod responses in soya bean. They will also contribute to soya bean breeding and regional introduction.