Abstract:In this study, expressed sequence tag (EST)-SSR markers were developed to investigate the genetic relationship between two commercially important scallop species, Yesso scallop Patinopecten yessoensis and Zhikong scallop Chlamys farreri. A total of 60 EST-SSRs previously developed from P. yessoensis were selected, and their cross-species amplification in C. farreri was analyzed. As a result, 21 pairs of EST-SSR primers showed unique PCR products. The interspecies transferability was calculated to be 35.00%. Among the 21 EST-SSR primers, 17 were polymorphic in the studied populations, which resulted in 28.33% transferability. In the two populations of P. yessoensis and C. farreri, the number of alleles ranged from 2.00 to 4.00, with mean allele numbers of 2.7647 and 2.3529, respectively. The mean effective number of alleles was estimated to be 1.9487 and 1.6350, while the mean observed heterozygosity was 0.6314 and 0.3333, respectively. Similar to the observed heterozygosity, the mean expected heterozygosity was higher in P. yessoensis (0.4569) than in C. farreri (0.3139). For the two populations, the diversity index was consistently higher in P. yessoensis than in C. farreri. The mean polymorphism information content was estimated to be 0.3726 and 0.2597, and Nei’s (1973) gene diversity index was calculated to be 0.4493 and 0.3087, respectively. Furthermore, Shannon’s information index in the two populations was 0.7176 and 0.5041, respectively. The genetic identity between the two species was calculated to be 0.619, with a high genetic divergence between them (0.480). Among the polymorphic markers, seven loci significantly deviated from the Hardy-Weinberg equilibrium according to the average fixation index (Fis). The genetic differentiation index (Fst) between the two populations was estimated to be 0.2398. The EST-SSR markers developed for cross-species amplification of P. yessoensis and C. farreri are important resources for the study of genetic diversity, marker-assisted breeding, gene discovery, and genetic evaluation of germplasm resources.
