Fingerprinting Chinese Sweetgum (Liquidambar formosana Hance) Accessions and Constructing a Core Collection Using Newly Developed SSR Markers

Liquidambar formosana, endemic to China, is a multifunctional tree species valued for its wood production, urban landscaping, and medicinal applications. Here, 111 superior L. formosana accessions were genotyped using 24 novel expressed sequence tag-simple sequence repeat (EST-SSR) markers to assess genetic diversity and structure, establish DNA fingerprints, and construct a core collection. A high degree of genetic diversity was detected in the tested accessions, with mean values for the number of observed alleles (Na), polymorphism information content (PIC), and Shannon's information index (I) recorded at 8.458, 0.579, and 1.336 per locus, respectively. Cluster analysis, principal coordinate analysis (PCoA), and population structure analysis collectively categorized these accessions into two major groups. Specifically, those from the SangZ provenance formed a distinct group, whereas accessions from other provenances exhibiting extensive gene exchange were assigned to the second group. The combined values of the probability of identity (PI) and the probability of identity among siblings (PIsibs) across 24 SSR loci were 1.475 x 10-19 and 2.561 x 10-8, respectively, indicating a strong ability for fingerprint identification. Unique fingerprints for the 111 accessions were established using four selected core markers. A final core collection consisting of 34 accessions was constructed using the allele maximization (M) strategy, accounting for 30.63% of the analyzed accessions. No significant differences in genetic diversity indicators, allele frequency distributions, and accession dispersion patterns were observed between the core and original collections, suggesting that the core collection could effectively represent the entire collection. This work will promote the identification, management, and conservation of L. formosana germplasm resources while providing valuable materials for the subsequent selection and breeding of this tree species.