The cultivated chrysanthemum is the most important ornamental species in the genus Chrysanthemum. However, because it is predominantly hexaploid and additionally exhibits self-incompatibility, it harbors numerous functionally redundant genes and displays extremely high heterozygosity. As a result, its genomic architecture is highly complex, making it challenging to interpret data obtained from omics analyses such as RNA-seq. To provide a genetically tractable model, we previously developed Gojo-0, a self-compatible, pure line of the diploid wild species C. seticuspe. In this study, we established Gojo-1, an improved self-compatible pure line derived from Gojo-0 and its sibling lines, exhibiting enhanced viability and culture performance. Leveraging these traits, we performed CRISPR–Cas9 editing of the AGAMOUS orthologs and successfully isolated mutants with altered floral organ morphology, demonstrating the line’s suitability for functional genomics. Comparative genome analysis showed that, aside from chromosome 1, the Gojo-1 genome is highly similar to that of Gojo-0, whose complete sequence has been determined. Taken together, these features indicate that Gojo-1 will serve as a valuable resource for future omics-based studies and a broad range of additional research applications.