Abstract: Branching is crucial for plant shoot morphogenesis and crop yield. It’s reported that TCP transcription factor play an important role in regulating branching. However, related study in diploid potato remains largely unknown. In order to illustrate the function of TCP transcription factor StBRC1a in diploid potato，we cloned StBRC1a in diploid potato Solanum tuberosum group phureja S15-65 and found that StBRC1a had two transcripts with different length named StBRC1aL and StBRC1aS. Sequence analysis revealed that StBRC1aL and StBRC1aS both had a 59-amino acid basic helix–loop–helix（bHLH）motif and an R domain. By constructing phylogenetic tree，it’s found that StBRC1aL and StBRC1aS had the closest relationship with SlBRC1a，which indicated it belonged to CYC/TB1-like TCP transcription factor. Tissue specific expression analysis showed that StBRC1aL and StBRC1aS were highly expressed in axillary buds. We constructed a StBRC1a homozygous mutant by CRISPR/Cas9 system. Compared with wild type，the mutant showed significantly increased branching，which demonstrated that StBRC1a played an important role in branching for diploid potatoes.

Key words: potato, diploid, TCP transcription factor, CRISPR/Cas9, branching