An improved Agrobacterium-mediated transformation method for genome editing using CRISPR/Cas9 in elite indica rice (Oryza sativa L.)

Rice feeds nearly half of the world’s population and underpins global food security. Climate change now poses a major threat to rice productivity worldwide. Genome editing has reshaped crop improvement strategies. Among these tools, the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein (CRISPR/Cas) system stands out for its precision, efficiency, and scalability. However, Agrobacterium-mediated transformation efficiency is often low, particularly in indica rice varieties. Here, we optimized an Agrobacterium-mediated transformation protocol for indica rice cultivars. The method was established in Lalat and MTU-1010. Seed-derived embryogenic calli were used to introduce the thermosensitive genic male sterile (OsTMS5) gene. A CRISPR/Cas9 vector carrying a gRNA and the selectable marker hptII was used for transformation. Callus induction reached 96.87% in MTU-1010 and 93.30% in Lalat MS medium supplemented with 3 mg/L 2,4-D and 0.5 mg/L BAP. In contrast, regeneration efficiency was higher in Lalat (90.28%) than in MTU-1010 (87.51%) on MS medium supplemented with 0.25 mg/L NAA, 0.5 mg/L kinetin, and 2 mg/L BAP. In addition, PCR analysis further verifies the integration of the transgene. Subsequently, the transformation efficiency was 37.20% in Lalat and 29.62% in MTU-1010. Therefore, this protocol provides a robust platform for gene function analysis and trait editing in rice. Its application may accelerate yield improvement and enhance stress tolerance under changing climatic conditions.