First evaluation of resistance to both a California OsHV-1 variant and a French OsHV-1 microvariant in Pacific oysters

• Published in: BMC Genetics
• Main Authors: Konstantin Divilov, Blaine Schoolfield, Benjamin Morga, Lionel Dégremont, Colleen A. Burge, Daniel Mancilla Cortez, Carolyn S. Friedman, Gary B. Fleener, Brett R. Dumbauld, Chris Langdon
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2019
• Subjects: Ostreid herpesvirus 1; Crassostrea gigas; Heritability; Breeding; Genetics; QH426-470; Pacific; Pacific oyster
• Online Access: https://doi.org/10.1186/s12863-019-0791-3; https://doaj.org/article/e76e660be3194f75aa4d14dfde10670e

Abstract Background Variants of the Ostreid herpesvirus 1 (OsHV-1) cause high losses of Pacific oysters globally, including in Tomales Bay, California, USA. A suite of new variants, the OsHV-1 microvariants (μvars), cause very high mortalities of Pacific oysters in major oyster-growing regions outside of the United States. There are currently no known Pacific oysters in the United States that are resistant to OsHV-1 as resistance has yet to be evaluated in these oysters. As part of an effort to begin genetic selection for resistance to OsHV-1, 71 families from the Molluscan Broodstock Program, a US West Coast Pacific oyster breeding program, were screened for survival after exposure to OsHV-1 in Tomales Bay. They were also tested in a quarantine laboratory in France where they were exposed to a French OsHV-1 microvariant using a plate assay, with survival recorded from three to seven days post-infection. Results Significant heritability for survival were found for all time points in the plate assay and in the survival phenotype from a single mortality count in Tomales Bay. Genetic correlations between survival against the French OsHV-1 μvar in the plate assay and the Tomales Bay variant in the field trait were weak or non-significant. Conclusions Future breeding efforts will seek to validate the potential of genetic improvement for survival to OsHV-1 through selection using the Molluscan Broodstock Program oysters. The lack of a strong correlation in survival between OsHV-1 variants under this study’s exposure conditions may require independent selection pressure for survival to each variant in order to make simultaneous genetic gains in resistance.