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Bolting time is a critical trait that affects crop yield, adaptability, and overall productivity, making its regulation vital for agricultural success. In this study, we explored the genetic mechanisms controlling flowering time in radish (Raphanus sativus) via a combination of quantitative trait locus (QTL) analysis and genome-wide association study (GWAS). By developing an F2 population from a cross between the relatively late-bolting variety ‘L432’ and the early-bolting variety ‘L285’, we identified 12 QTLs associated with bolting time. Furthermore, a GWAS performed on 60 East Asian radish accessions revealed 14 candidate genes potentially involved in flowering and bolting regulation. FLOWERING LOCUS C (FLC2) was the major candidate gene explaining the early and late bolting types. One locus was commonly detected from QTL and GWAS on chromosome 4, where CONSTANS-like (COL4) is located. To validate these findings, SNP markers were designed and applied to F2 populations, revealing a correlation between marker presence and bolting phenotypes. These results offer valuable insights into the molecular control of bolting time in radish and identify candidate genes for use in marker-assisted breeding. These findings could enhance breeding efforts for optimizing bolting time in various radish markets.

Ogura male sterile cytoplasm is widely used for radish breeding. In this study, high-resolution melting (HRM) markers associated with Rft and Rfo, major restorer-of-fertility genes in Ogura cytoplasmic male sterility (CMS) in radish, were developed. Genetic mapping was carried out using F2 populations derived from crosses between male-sterile Ogura CMS lines and male-fertile lines. Identification of the Rft and Rfo loci was achieved through SNP-based genotyping and linkage grouping. HRM markers were subsequently developed based on flanking sequences of SNPs linked to these loci. For the Rft gene, a set of 117 SNPs was selected within a candidate region on chromosome 5, and 14 HRM markers were successfully developed. Genotyping of F2 showed high correlation between three markers and the phenotype. Regarding the Rfo gene, a set of 27 HRM markers was designed based on flanking sequences of SNPs located on chromosomes 9 and 0. Genotyping in the Rfo segregating population identified a single marker, RSRF27, that accurately distinguished the male sterility phenotype. Validation of the developed markers was performed in populations containing both Rft and Rfo genes, confirming their utility for genotyping and demonstrating that these two genes independently contribute to male sterility recovery. Overall, this study provides HRM markers that can be used for genotyping Rft and Rfo and contributes to a deeper understanding of male sterility restoration mechanisms in Ogura CMS.