Genetic differentiation between Zhe oyster Crassostrea plicatula and Pacific oyster Crassostrea gigas populations in China assessed by microsatellite analysis

Genetic differentiation and relationships between Crassostrea plicatula and Crassostrea gigas populations from China were studied by means of the microsatellite technique. Seven loci were used to screen five populations each collected from C. plicatula and C. gigas. All loci showed high polymorphism for all populations, as observed in average number of alleles per locus (19.1-28.1), and average expected heterozygosity (0.891-0.954). Significant departures from Hardy-Weinberg equilibrium due to heterozygote deficiency were observed over most populations at each locus and were best explained by null alleles. F-ST values showed significant genetic differentiation between C. plicatula and C. gigas populations. According to the neighbor-joining tree constructed on the basis of the genetic distance (D-A), the ten populations fell into two distinct groups (C. plicatula and C. gigas groups), and the results of principal coordinate analysis and assignment tests also supported the neighbor-joining clustering. The outcomes presented here suggested that the microsatellite markers have great potential for differentiating C. plicatula from C. gigas populations. The information obtained in this study has important implications for the suitable management and conservation of these genetic resources in China.