Development and evaluation of EST-SSR markers in Sorbus pohuashanensis (Hance) Hedl. and their application to other Sorbus species

Abstract

We developed and identified a new set of polymorphic EST-SSR markers in Sorbus pohuashanensis (Hance) Hedl. and generated an optimal sampling strategy. Sorbus pohuashanensis (Hance) Hedl. is indigenous to northern China and prized for its graceful appearance and seasonal variations in foliage color. However, only a few molecular biology studies have been conducted on this species. Therefore, its development and increased utilization are limited. The objective of the present study was to develop expressed sequence tag-simple sequence repeat (EST-SSR) markers based on the transcriptome data of this species. A total of 167 primer pairs were designed and 24 were randomly selected from the 55 initially screened for validation. Their polymorphism was assessed using samples of the Mount Kunyu in Shandong Province (SDKYS) population. Fifteen EST-SSR markers were identified as polymorphic, with a mean number of alleles (Na) and a polymorphism information content (PIC) of 8.2 and 0.6907, respectively. Thirty EST-SSRs (including another 15 EST-SSRs being previously developed) derived from S. pohuashanensis had high transferability (90%) to another 14 Sorbus species, and there were nine EST-SSRs applicable to Sorbus species tested. These Sorbus species were divided into two main clusters by an unweighted pair-group method with the arithmetic mean (UPGMA) clustering tree based on the nine EST-SSRs and was validated by principal coordinate analysis (PCoA). The sampling strategy showed that 25 randomly selected individuals from a population of S. pohuashanensis could represent 95% of its genetic diversity level. In all, these findings would provide a powerful theoretical basis for future studies on the genetic diversity and germplasm resources of S. pohuashanensis and its related species.