Chinese Cornus officinalis: genetic resources, genetic diversity and core collection

Cornus officinalis is plant species that is widely used in traditional Chinese medicine. To help the efficient utilization and conservation of this species, the genetic diversity of 73 germplasm resources collected from Zhejiang, Henan and Shaanxi provinces in China were used in a primary core collection. The germplasm resources were classified nine types and the analysis of morphological traits and chemical components showed wide variations among the germplasm types. The primary core collection of C. officinalis was evaluated by using 18 inter-simple sequence repeat (ISSR) markers and a mini core collection was developed based on three strategies on construction of a core germplasm resources. The ISSR results showed that a total of 233 alleles were identified in these 73 accessions, the genetic diversity (P = 91.02%, H = 0.293, I = 0.446) revealed with an average of 2 alleles per locus. The genetic diversity index analysis suggested that there is a great richness and uniqueness of genetic variation in this primary core collection. Cluster analysis by UPGMA and STRUCTURE placed the 73-germplasm resources into four linkage clusters. Almost all samples from one sampling location were clustered together. Compared to the RS and SW strategy, the LDSS strategy proved to be more representative in the core collection of C. officinalis. Finally, a mini core collections by LDSS, composed of 18 accessions (24.66% of the primary core collection), let more than 94.85% of polymorphic loci remained, 97.55% of the observed number of alleles and 99.28% of the effective number of alleles of the mini core collection, respectively. The Nei's gene diversity and Shannon's Information index of core collection were 0.294 and 0.443, respectively. Taken all together, the results indicated that mini core collections constructed by the LDSS strategy represented their primary core collections and provided a rational framework for intensive surveys of natural variation in C. officinalis genetic resources.