In order to protect and utilize the germplasm resource better, it is highly necessary to carry out a study on the genetic diversity of Camellia chekiangoleosa Hu. However, systematic research on population genetics analysis of the species is comparatively rare. Herein, 16 highly variable simple sequence repeat (SSR) markers were used for genetic structure assessment in 12 natural C. chekiangoleosa populations. The genetic diversity of C. chekiangoleosa was low (h = 0.596), within which, central populations (such as Damaoshan (DMS), Sanqingshan (SQS), and Gutianshan (GTS)) at the junction of four main mountain ranges presented high diversity and represented the center of the C. chekiangoleosa diversity distribution; the Hengshan (HS) population in the west showed the lowest diversity, and the diversity of the eastern and coastal populations was intermediate. C. chekiangoleosa exhibited a high level of genetic differentiation, and the variation among populations accounted for approximately 24% of the total variation. The major reasons for this situation are the small population scale and bottleneck effects in some populations (HS and Lingshan (LS)), coupled with inbreeding within the population and low gene flow among populations (Nm = 0.796). To scientifically protect the genetic diversity of C. chekiangoleosa, in situ conservation measures should be implemented for high-diversity populations, while low-diversity populations should be restored by reintroduction.

Camellia chekiangoleosa is a popular variety of Oil-camellia that has high oil production and ornamental value. Microsatellite (SSR) markers are the preferred tool for the molecular marker-assisted breeding of C. chekiangoleosa. By focusing on the problems of the low development efficiency of polymorphic SSR markers and the lack of available functional markers in Oil-camellia, we identified 97,510 SSR loci based on the full-length transcriptome sequence of C. chekiangoleosa. An analysis of SSR characteristics showed that mononucleotide (51.29%) and dinucleotide (34.36%) SSRs were the main repeat types. The main SSR distribution areas based on proportion covered were ordered as follows: 5'UTR > 3'UTR > CDS. By comparing our data with those in databases such as GO and KEGG, we obtained functional annotations of unigene sequences containing SSR sites. The data showed that the amplification efficiency of the SSR primers was 51.72%, and the development efficiency of polymorphic SSR primers was 26.72%. Experiments verified that dinucleotide and pentanucleotide SSRs located in UTR regions could produce more polymorphic markers. An investigation into the genetic diversity of several C. chekiangoleosa populations also suggested that the developed SSR markers had higher levels of polymorphism. This study will provide a reference and high-quality markers for the large-scale development of functional SSR markers and genetic research in Oil-camellia.

Camellia chekiangoleosa is a popular variety of oil-tea camellia and has high oil production and ornamental value. Microsatellite (SSR) markers are the preferred tool for the molecular marker-assisted breeding of C. chekiangoleosa. By focusing on the problems of the low development efficiency of polymorphic SSR markers and lack of available functional markers in oil-tea camellia, we identified 97510 SSR loci based on the full-length transcriptome sequence of C. chekiangoleosa. An analysis of microsatellite characteristics showed that mononucleotide (51.29%) and dinucleotide (34.36%) SSRs were the main repeat types. The main SSR distribution areas based on proportion covered were ordered as follows: 5'UTR > 3'UTR > CDS. By comparing our data with that in databases such as GO and KEGG, we obtained functional annotations of unigene sequences containing SSR sites. The data showed that the amplification efficiency of the SSR primers was 51.72%, and the development efficiency of polymorphic SSR primers was 26.72%. Experiments verified that dinucleotide and pentanucleotide SSRs located in UTR regions could produce more polymorphic markers. An investigation into the genetic diversity of several C. chekiangoleosa populations also suggested that the developed SSR markers had higher levels of polymorphism. This study will provide a reference and high-quality markers for the large-scale development of functional SSR markers and genetic research in oil-tea camellia.