Construction of a Core Collection of Germplasms from Chinese Fir Seed Orchards

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the most important tree species for afforestation in China. First-, second-, and third-generation seed orchards of Chinese fir have been established successively, and rich germplasms have been accumulated in the process of genetic improvement. It is necessary to build a core collection of germplasms from Chinese fir seed orchards. In this work, we constructed core collections representing the genetic diversity of Chinese fir seed orchard resources based on SSR data. A total of 607 seed orchard materials from three generations were used to determine the best sampling method and intensity by comparing and analyzing nine methods for constructing core collections. Core Hunter's multi-strategy optimizes allele coverage and the distance criterion under a 30% sampling intensity (weight: A-NE, 0.7; CV, 0.3 and E-NE, 0.5; CV, 0.5), which is superior to other strategies and was selected as the best method. The two core collections (A-NE&CV73, E-NE&CV55) constructed contained all the alleles of the whole collection and effectively limited the homology in the core collections; each core collection contained 182 accessions. Our findings could contribute greatly towards improving the management of genetic resources in Chinese fir seed orchards and provide elite materials for future studies.