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Cinnamomum camphora is a valuable broad-leaf tree indigenous to South China and East Asia and has been widely cultivated and utilized by humans since ancient times. However, owing to its overutilization for essential oil extraction, the Transplanting Big Trees into Cities Program, and over deforestation to make furniture, its wild populations have been detrimentally affected and are declining rapidly. In the present study, the genetic diversity and population structure of 180 trees sampled from 41 populations in South China were investigated with 22 expressed sequence tag-simple sequence repeat (EST-SSR) markers. In total, 61 alleles were harbored across 180 individuals, and medium genetic diversity level was inferred from the observed heterozygosity (Ho), expected heterozygosity (He), and Nei&rsquo, gene diversity (GD), which were 0.45, 0.44, and 0.44, respectively. Among the 41 wild populations, C. camphora had an average of 44 alleles, 2.02 effective alleles, and He ranging from 0.30 (SC) to 0.61 (HK). Analysis of molecular variance (AMOVA) showed that 17% of the variation among populations and the average pairwise genetic differentiation coefficient (FST) between populations was 0.162, indicating relatively low genetic population differentiations. Structure analysis suggested two groups for the 180 individuals, which was consistent with the principal coordinate analysis (PCoA) and unweighted pair-group method with arithmetic means (UPGMA). Populations grouped to cluster I were nearly all distributed in Jiangxi Province (except population XS in Zhejiang Province), and cluster II mainly comprised populations from other regions, indicating a significant geographical distribution. Moreover, the Mantel test showed that this geographical distance was significantly correlated with genetic distance. The findings of this research will assist in future C. camphora conservation management and breeding programs.

Cinnamomum camphora (Lauraceae) is a well-known multipurpose tree with aromatic oils, insect-repellent effects and ornamental value. In this study, a total of 74,289 simple sequence repeats (SSRs) were found in 56,124 unigenes, of which 14,225 unigenes contained more than one SSR locus. Among these SSR loci, the mono-nucleotide repeats were the most frequent, with a frequency of 61.14%, followed by 24.87% di-nucleotide repeats and 12.87% tri-nucleotide repeats. Twenty-one polymorphic SSR markers were developed and validated in 45 camphor trees. The 21 loci were further examined for cross-species transferability in other six related species. The novel genic-SSR markers will not only benefit genetic diversity analysis and wild resources conservation of C. camphora, but also contribute to exploring the further evolutionary history and genetic differentiation pattern of Cinnamomum.

Transcriptome sequencing was performed using Illumina paired-end RNA sequencing technology, for facilitating gene discovery and SSR marker development in an endangered tree, Woonyoungia septentrionalis. A total of 41,578,222 high-quality reads were obtained, and 93,156 non-redundant unigenes were assembled and annotated by sequence similarity searching in diverse public databases. Analyses showed that 36,176 unigenes (38.83%) had at least blast hit against Nr, Nt, KO, SwissProt, PFAM, KO, or GO database; and 2945 unigenes (4.13%) were annotated in all seven databases. Totally, 17,719 genic-SSRs were identified in 14,629 (15.70%) out of 93,156 unigenes. Finally, 51 primers of the 64 designed SSR primers produced clear SSR bands, of which 20 SSR loci were polymorphic in 149 individuals representing four natural populations. Observed and expected heterozygosity varied from 0 to 0.846 and from 0 to 0.792, respectively. At the species level, the Ho and He of the four W. septentrionalis populations were 0.3325 and 0.3559, respectively. The average genetic diversity within populations, H and I were 0.3500 and 0.5937, respectively. Cross-species amplification of the 20 markers was tested in other related species. The transcriptomic resources and genic SSR markers are valuable tools not only for ecological conservation of this species, but also for phylogenetic studies.