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.

中文翻译：

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首次评估了太平洋牡蛎对加利福尼亚OsHV-1变种和法国OsHV-1微变种的抗性。

背景技术Ostreid疱疹病毒1（OsHV-1）的变体在全球范围内造成太平洋牡蛎大量损失，包括在美国加利福尼亚的Tomales湾。一组新的变体OsHV-1微变体（μvars）在美国以外的主要牡蛎养殖地区造成了很高的太平洋牡蛎死亡率。目前，美国尚无对OsHV-1有抗性的太平洋牡蛎，因为尚未评估这些牡蛎的抗性。为了开始对OsHV-1的抗性进行基因选择，从Molluscan亲鱼计划（美国西海岸太平洋牡蛎育种计划）的71个科系中筛选了在Tomales湾中接触OsHV-1后的存活情况。它们还在法国的检疫实验室进行了测试，并通过平板分析法将其暴露于法国的OsHV-1微变种中，感染后3到7天记录生存率。结果在托马斯湾的一次死亡计数中，在平板测定法和存活表型中的所有时间点都发现了显着的存活遗传力。平板测定法中针对法国OsHV-1μvar的存活率与田间性状的Tomales Bay变体之间的遗传相关性弱或不显着。结论未来的育种工作将寻求通过使用软体动物亲虾计划牡蛎进行选择来验证遗传改良对OsHV-1存活的潜力。在这项研究的暴露条件下，OsHV-1变体之间的存活缺乏强相关性，可能需要为每个变体的存活选择独立的选择压力，以便同时获得抗性的遗传增益。