Insight into the Complex Genetic Relationship of Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook.) Advanced Parent Trees Based on SSR and SNP Datasets

Accurate estimation of genetic relationships among breeding materials and their genetic diversity contributes to the optimal design of breeding programs. For Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), an important indigenous tree species in China, breeders have attempted to employ different molecular markers to address the genetic architecture of their target population, but the power of an advanced parent tree population with a complex pedigree relationship is still rather limited. In this study, a partly known pedigree map combined with marker-derived (SSRs and SNPs) information was implemented for the first time in the assessment of the genetic relatedness of a complex advanced parent tree population (n = 50) in Chinese fir. The bivariate analysis showed that relatedness coefficients between individuals based on SSRs were significantly correlated with SNPs (r = 0.690, p < 0.01). Moreover, the heatmap generated by the SSR-based coefficient matrix was largely consistent with that derived from the SNP-based matrix. Additionally, STRUCTURE and ADMIXTURE analyses based on the two markers showed an analogical genetic clustering result. When compared to the recorded pedigree information, the genetic relationships estimated by the two molecular markers were broadly parallel with pedigree relatedness. These results indicated that SSRs and SNPs can be used as effective tools to clarify genetic relationships when complete pedigree records are not available in Chinese fir. Based on the two markers, the present study revealed a relatively wide genetic variation (SSRs: PIC = 0.573; SNPs: PIC = 0.231) in the selected parent trees. This investigation provides important input into the progress of Chinese fir advanced-generation breeding.