Development of EST-SSRs from the ark shell (Scapharca broughtonii) transcriptome and their application in genetic analysis of four populations.

Background: The ark shell (Scapharca broughtonii) is one of the most economically important mollusks in the Bohai Sea and Yellow Sea of China. In recent years, ark shells from the Korean population were introduced to China for seed propagation and culture.

Objective: To explore the impact of the introduction of Korean ark shell on the genetic diversity of native population in China.

Methods: Simple sequence repeat (SSR) is effective and widely used tool for genetic analysis. In this study, 180 EST-SSRs were selected and verified by polymerase chain reaction and polyacrylamide gel electrophoresis. Subsequently, five polymorphic EST-SSRs were screened and their primers were modified by fluorescein for use in the genetic analysis of four populations.

Results: Genetic analysis showed that 361 alleles amplified by five SSR loci were detected in the four populations. The number of alleles for the five SSRs ranged from 8 to 30, with a mean of 18.05 (standard deviation, SD = 6.492). The effective number of alleles varied from 2.253 to 22.222, with a mean of 10.596 (SD = 4.713). Observed heterozygosity and expected heterozygosity were 0.167-0.833 and 0.566-0.971, with average values of 0.520 (SD = 0.177) and 0.891 (SD = 0.062), respectively. Polymorphic information content ranged from 0.521 to 0.953, with a mean of 0.865 (SD = 0.070). The pairwise genetic differentiation coefficient (F) of the four populations ranged from 0.0267 to 0.0477, showing low genetic differentiation. The phylogenetic tree constructed by neighbor-joining method showed that the genetic distance between the Chinese Dalian native population and three Korean populations was relatively more far than that among those Korean populations.

Conclusion: The results indicated that the genetic structure of the Dalian wild population was less affected by the introduced Korean wild populations.