The Development of EST-SSR Markers from Transcriptome Sequencing and Genetic Diversity of Twenty Genotypes with High Yields of Cornus wilsoniana, an Important Wood Oil Plant

Oil plants are not only used as essential nutriments in food but also used broadly as ingredients of industrial products.  Cornus wilsoniana  Wanger is an important native woody oil plant with high-yield and high-oiliness characters in China. The fruit oil of  Cornus wilsoniana  not only could be used as equilibrated dietary oil, but also has hypolipidemic function and helps to overcome EFA deficiency. Genomic information is currently not available for  Cornus wilsoniana , which will therefore affect its genetic improvement process. In this study, 8713 EST-SSRs were identified from the transcriptome sequencing of  Cornus wilsoniana . Most of these EST-SSRs were composed of dimer and trimer repeats. The AG/CT motif is the most common dimeric EST-SSRs motif (53.5%), whereas the CG/CG (0.44%) microsatellites are present only at low abundances. Among the trimeric microsatellites, AAG/CTT (5.53%) and ATC/ATG (4.27%) are the most common motifs. There are no obvious dominant motifs among the tetra-, penta-, and hexa- nucleotide motifs. Fifteen pairs of EST-SSRs primers are developed with polymorphism and used for the genetic diversity analysis of twenty genotypes of  Cornus wilsoniana  with high fruit output. Allele number per locus ranges from 2 to6 with an average of 2.87, and the PIC value ranges from 0.05 to 0.58 with an average of 0.36. Average genetic diversity overall SSR loci for the 20 genotypes was 0.427, ranging from 0.049 to 0.659. All the loci are polymorphic and clearly distinguish the genotypes. Cluster analyze (NJ tree, UPGMA) identifies a similar pattern of variation. 15developed EST-SSRs are informative, codominant and reliable, and could be applied in the improvement programs of  Cornus wilsoniana  in the future.