Molecular markers for parentage assignment in hard clam (Mercenariamercenaria) stocks

摘要

The hard clam, Mercenaria mercenaria, is currently the most important aquaculture species on the east coast of the United States, yet development of selected clam brood stock is still very much in its infancy. An efficient breeding program that maximizes selection intensity, while maintaining genetic diversity, could result in substantial benefits to the industry. Selective breeding in molluscs, however, is complicated by their high fecundity and high variance in reproductive success, which rapidly can result in inbreeding. Because larval molluscs are impossible to physically tag or mark individually, one of the only practical methods of controlling inbreeding is to rear families separately; however, this requires enormous amounts of labor in both the hatchery and field. In addition, separately reared families must be replicated extensively to randomize environmental effects. Alternatively, using molecular genetic markers, families can be mixed for rearing, desired traits can be measured, and individuals can be retrospectively assigned to families based on multi-locus genotypes. We have recently developed both microsatellite and single nucleotide polymorphism (SNP) markers in M. mercenaria. Male and female individuals from hatchery strains originating in different regions were used as parents in controlled laboratory spawns to produce 50 distinct full-sib families. Parental tissue and larvae from each of the 50 crosses were preserved to provide progeny samples with independently known parentage for testing the power of the markers for accuracy at pedigree reconstruction.