Identification of variants associated with hard clam, Mercenaria mercenaria, resistance to Quahog Parasite Unknown disease.

Severe losses in aquacultured and wild hard clam (Mercenaria mercenaria) stocks have been previously reported in the northeastern United States due to a protistan parasite called QPX (Quahog Parasite Unknown). Previous work demonstrated that clam resistance to QPX is under genetic control. This study identifies single nucleotide polymorphism (SNP) associated with clam survivorship from two geographically segregated populations, both deployed in an enzootic site. The analysis contrasted samples collected before and after undergoing QPX-related mortalities and relied on a robust draft clam genome assembly. ~200 genes displayed significant variant enrichment at each sampling point in both populations, including 18 genes shared between both populations. Markers from both populations were identified in genes related to apoptosis pathways, protein-protein interaction, receptors, and signaling. This research begins to identify genetic markers associated with clam resistance to QPX disease, leading the way for the development of resistant clam stocks through marker-assisted selection.