**5. Conclusions**

This study investigated the genetic diversity and population structure of natural *P. koraiensis* populations in northeast China, and proposed some conservation strategies for this valuable conifer species. This study is the first comprehensive report of the genetic diversity of natural *P. koraiensis* populations in China. We found that the existing *P. koraiensis* populations in China maintain high levels of genetic diversity, which provide a foundation for germplasm innovation and genetic improvement of *P. koraiensis*. The population genetic analysis in this study identified two independent genetic units (Liangshui and Helong populations) that exhibit high degrees of genetic differentiation. The populations distributed in the Xiaoxinganling Mountains are highly genetically diverse and may represent the central population of natural *P. koraiensis* in China. Furthermore, the genetic structure of *P. koraiensis* populations identified in this study is consistent with the geographical distribution of these populations in China. These results have significance for the protection of natural *P. koraiensis* germplasm resources in China as well as for developing improved genotypes through breeding. Our findings provide genetic information useful for future genome-wide association studies (GWAS) and marker-assisted selection (MAS) and genomic selection (GS) studies. It is, therefore, recommended to further conduct research on genetic improvement for timber and cone production using marker-assisted selection and/or genomic selection as well as genotype by environment interaction studies should be carried out to identify suitable site-specific genotypes.

**Author Contributions:** Conceptualization, X.Z. and X.L.; methodology, X.L., Y.L. and M.Z.; validation, X.L., Y.X. and M.T.; resources, X.L.; writing—original draft preparation, X.L.; writing—review and editing, X.L., M.T., and X.Z.; supervision, X.Z.; project administration, X.Z.; funding acquisition, X.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research study was supported by the Fundamental Research Funds for the Central Universities (Northeast Forestry University) (No. 2572017DA02).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data for this study can be made available with reasonable request to the authors.

**Conflicts of Interest:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
