Research Article: Analysis of genetic diversity and population structure in a domesticated Asian seabass (Lates calcarifer) population from Iran using microsatellite markers

This study aimed to assess the population structure and genetic diversity of captive Lates calcarifer. The investigation included three cultured cohorts initially imported in ۲۰۱۶, ۲۰۱۸, and ۲۰۱۹ (hereafter termed ۹۶, ۹۸, and ۹۹, respectively) as fry to a Marine Fish Research Station (MFRS) at ۱۲ gene loci. The results indicated that all microsatellite markers were polymorphic in all populations. Across three cohorts, the average allele number was ۱۸.۵ per locus with nearly half (۴۹%) of ۶۵ unique alleles detected in cohort ۹۹. The average observed alleles (Na), allele richness (Ne), and Shannon Information index (I) in the whole population were ۶.۲۵, ۴.۲۲, and ۱.۵۴, respectively. The mean observed heterozygosity (Ho) in all three cohorts was obtained as ۰.۷۳۳, which accorded with expected heterozygosity (He). The highest and lowest observed alleles were detected in ۹۹ and ۹۶, respectively. The highest mean Na (۷.۵), Ne (۵.۰۲), and Shannon index (۱.۷۲), and lowest mean Na (۵.۳۳), Ne (۳.۶۷), and I (۱.۳۹) were observed in cohorts ۹۹ and ۹۶, respectively. Stock ۹۸ represented the Na, Ne, and I as ۵.۹۲, ۳.۹۷, and ۱.۵, respectively. The maximum and minimum Ho belonged to ۹۸ (۰.۷۸۷) and ۹۶ (۰.۶۷۵) cohorts, respectively. The fixation index (F) was low in three cohorts and even showed a negative value in ۹۸ (-۰.۰۶۹). Wright's F-statistics, including FIS, FIT, and FST, estimations were evaluated as -۰.۰۱, ۰.۰۵, and ۰.۰۶, illustrating the non-inbreeding coefficient within the population and overall population and the low coefficient of co-ancestry, respectively. Chi-square tests revealed that all ۱۲ markers conformed to Hardy-Weinberg equilibrium (HWE) in the ۹۸ cohorts. In contrast, cohorts ۹۶ and ۹۹ deviated meaningfully from HWE in one locus (Lca۰۹۸) and two loci (Lca۱۳۰ and Lca۱۳۷) (p<۰.۰۱), respectively. Nei's standard genetic distance and Pairwise FST distance between the three cohorts showed the lowest and highest genetic distance between pair cohorts ۹۶-۹۸ and ۹۶-۹۹, respectively. Analysis of molecular variance determined that between-population component of genetic variance (۳%) was firmly lower than the within-population component (۹۷%), resulting in meaningful genetic differentiation between populations (FST = ۰.۰۳۳) (p<۰.۰۱). Based on the population genetic structure analysis, under the admixture model, the most negligible probability is associated with K=۲ in seabass cohorts, meaning two significant distinct genetic structures. We found that these populations in the MFRS may create a base population, a prerequisite for further selective inbreeding programs.

کلیدواژه ها:

Genetic variation ، Genetic differentiation ، Founder population ، Lates calcarifer