An Agrobacterium -mediated non-antibiotic selection-based transformation system for rice ( Oryza sativa ssp. indica ) cultivar “93-11” successfully produces TAC1 -silenced transgenic plants

The rice ( Oryza sativa L. ssp. indica ) cultivar “93-11” is a reference genotype used in many studies; however, its recalcitrance during transformation and regeneration greatly limits functional genomics and breeding research. In this study, we developed an efficient Agrobacterium tumefaciens –mediated transformation system for “93-11”, based on the phosphor mannose isomerase (PMI) positive selection system. Calli of “93-11” were transformed with the Agrobacterium strain EHA105 harboring a binary vector, containing the PMI gene and an RNAi sequence targeting TILLER ANGLE CONTROLLING 1 ( TAC1 ). We also developed a method for removing Agrobacterium from the callus following co-cultivation and determined the optimal conditions for PMI selection and callus differentiation. Compared with the hygromycin phosphotransferase (HPT) selection system, newly generated calli were recovered at higher rates on the PMI selection medium, with “93-11” transformation frequency reaching 7.50%. Notably, the down-regulation of TAC1 in the “93-11” genetic background led to a more compact plant architecture. Overall, this work presents a genetic transformation system suitable for the reference indica variety “93-11” using a non-antibiotic selectable agent. This advance will facilitate functional genomic research and the improvement of agronomic traits for indica varieties recalcitrant to transformation.