Genetic parameters for dermo challenge survival in a Virginia, U.S. eastern oyster breeding population

Dermo, a chronic condition caused by the protozoan parasite Perkinsus marinus , is the most prominent disease affecting eastern oysters in Virginia, U.S. Genetic improvement for well-defined, dermo-resistance phenotypes could offer a viable long-term strategy for managing the disease if ample genetic variation exists in aquaculture populations. Here we report results from controlled laboratory disease challenge experiments that enabled direct measurement of disease response phenotypes and estimation of genetic parameters for Dermo resistance. Nearly 6000 individual one-year-old pedigreed oysters representing three year classes (2019, 2020, and 2021) and 109 unique full-sibling families from the Aquaculture Genetics and Breeding Technology Center (ABC) breeding program at the Virginia Institute of Marine Science were injected with a consistent concentration of cultured parasite and monitored for survival for 42 days. Parasite load of each oyster was quantified at either the time of death or the end of the experiment. Siblings of the challenged oysters were also evaluated for survival at a grow-out site with historically high disease pressure. Challenge survival was estimated to be moderately heritable (0.14 ± 0.03 on the observed scale, 0.24 ± 0.05 underlying liability scale). Field performance traits (growth, shape, and survival) were not correlated with challenge survival. Our results demonstrate the potential for genetic improvement through selection for dermo challenge survival. However, a better understanding of the lack of correlation between challenge and field survival is needed before incorporating challenge survival into a multi-trait selection index. • Dermo is the most prominent disease affecting eastern oysters in Virginia. • Laboratory disease challenges provide an alternative to measuring dermo resistance in the field. • Survival in response to laboratory disease challenge is moderately heritable and not correlated with field performance traits. • More work is needed before incorporating challenge survival into a multi-trait selection matrix.