A rapid and highly efficient sorghum transformation strategy using GRF4‐GIF1/ternary vector system

SUMMARY Sorghum is an important crop for food, forage, wine and biofuel production. To enhance its transformation efficiency without negative developmental by‐effects, we investigated the impact of GRF4‐GIF1 chimaera and GRF5 on sorghum transformation. Both GRF4‐GIF1 and GRF5 effectively improved the transformation efficiency of sorghum and accelerated the transformation process of sorghum to less than 2 months which was not observed when using BBM‐WUS. As agrobacterium effectors increase the ability of T‐DNA transfer into plant cells, we checked whether ternary vector system can additively enhance sorghum transformation. The combination of GRF4‐GIF1 with helper plasmid pVS1‐VIR2 achieved the highest transformation efficiency, reaching 38.28%, which is 7.71‐fold of the original method. Compared with BBM‐WUS, overexpressing GRF4‐GIF1 caused no noticeable growth defects in sorghum. We further developed a sorghum CRISPR/Cas9 gene‐editing tool based on this GRF4‐GIF1/ternary vector system, which achieved an average gene mutation efficiency of 41.36%, and null mutants were created in the T0 generation.