Genetic evaluation and core germplasm screening of ancient heritage Pseudolarix amabilis trees in Ningbo, China
Background Pseudolarix amabilis is a relict gymnosperm endemic to China and a National Class II Key Protected Wild Plant. To systematically assess the genetic resource of ancient trees in Ningbo and to construct a core germplasm collection, we employed doubledigest restrictionsite associated DNA sequencing (ddRADseq) to perform genomewide analyses of genetic diversity, population structure, and differentiation on 128 registered individuals, followed by core collection screening. Results The ancient population exhibited aboveaverage expected heterozygosity (HE = 0.3035) and nucleotide diversity (pi = 0.3126) but observed heterozygosity (HO = 0.1742) was significantly lower, with a high inbreeding coefficient (FIS = 0.4416) indicating pronounced heterozygote deficiency and inbreeding depression risk. Grade I trees (500 years) harboured the highest genetic diversity and served as core reservoirs of rare alleles, Grade II trees exhibited intermediate diversity with the lowest inbreeding, whereas Grade III trees showed the most severe inbreeding. Population structure analysis revealed six ancestral clusters with extensive admixture and weak differentiation among conservation grades, a pattern likely shaped by historical anthropogenic introductions and cultivation practices. A core collection of 38 individuals (30% sampling ratio) was selected, with nucleotide diversity and minor allele frequency surpassing those of the original population; validation by phylogenetic tree and PCA confirmed its representativeness.Conclusion This study establishes the first molecular genetic profiles for Ningbo's ancient P. amabilis, clarifies conservation priorities and inbreeding risks, and proposes differentiated strategies, thereby providing a scientific basis for precision conservation and genetic management of this relict species.