**5. Conclusions**

In this study, a genetic map related to regeneration rate was developed through microspore culture. The genetic map used a large number of SNP markers generated using the GBS analysis method. Due to the F1 mapping, a maternal linkage map and a paternal linkage map are created separately and contain nine LGs. The phenotype was determined by the regeneration rate of embryos resulting from the microspore culture. QTL analysis was performed from an F1 population created by a cross between high and low regeneration varieties of radish by combining the genetic map with phenotypic data. Among the radish genes in the QTL region, genes known to be related to plant regeneration were designated as candidates. We found a total of five QTLs and predicted five candidate genes. These candidate genes are divided into two classes and appear to be either PRC2 subunits or auxin synthesis. Although the detected QTL information should be confirmed through repeated experiments, it may be useful for genetic research and MAS by developing molecular markers in the near future. Based on these results, it is expected that it will help to establish a system to proactively test the e fficiency of the microspore culture. In addition, we are planning to develop PCR-based molecular markers associated with microspore culture so that breeders can speed up selecting radish lines with easier haploid generations. Moreover, we expect that the candidate genes will be further investigated in the near future with reverse genetics approaches to find out exact functions related to microspore culture.

**Author Contributions:** Conceptualization, C.K. and S.P.; methodology, K.K., S.-J.L., S.-H.C., and D.-H.J.; software, Y.K.; validation, K.K.; formal analysis, M.-Y.P.; investigation, C.K.; resources, S.P.; data curation, Y.K.; writing—original draft preparation, K.K.; writing—review and editing, C.K.; visualization, Y.K.; supervision, Y.P.L.; writing discussion, C.K.; project administration, C.K.; funding acquisition, C.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through Golden Seed Project, funded by the Ministry of Agriculture, Food and Rural A ffairs (MAFRA) (213006-05-3-WTH11).

**Conflicts of Interest:** The authors declare no conflict of interest.
