Azéma Patrick, Lamy Jean-Baptiste, Boudry Pierre, Renault Tristan, Travers Marie-Agnès, Dégremont Lionel
Laboratoire de Génétique et Pathologie des Mollusques Marins, Ifremer, avenue Mus de Loup, 17390, La Tremblade, France.
Laboratoire des Sciences de l'Environnement Marin, UMR 6539 LEMAR (UBO/CNRS/IRD/Ifremer), Centre de Bretagne, Ifremer, CS 10070, 29280, Plouzané, France.
Genet Sel Evol. 2017 Feb 15;49(1):23. doi: 10.1186/s12711-017-0297-2.
In France, two main diseases threaten Pacific oyster production. Since 2008, Crassostrea gigas spat have suffered massive losses due to the ostreid herpesvirus OsHV-1, and since 2012, significant mortalities in commercial-size adults have been related to infection by the bacterium Vibrio aestuarianus. The genetic basis for resistance to V. aestuarianus and OsHV-1 and the nature of the genetic correlation between these two traits were investigated by using 20 half-sib sire families, each containing two full-sib families. For each disease, controlled infectious challenges were conducted using naïve oysters that were 3 to 26 months old. In addition, siblings were tested under field, pond and raceway conditions to determine whether laboratory trials reflected mortality events that occur in the oyster industry.
First, we estimated the genetic basis of resistance to V. aestuarianus in C. gigas. Susceptibility to the infection was low for oysters in spat stage but increased with later life stages. Second, we confirmed a strong genetic basis of resistance to OsHV-1 infection at early stages and demonstrated that it was also strong at later stages. Most families had increased resistance to OsHV-1 infection from the spat to adult stages, while others consistently showed low or high mortality rates related to OsHV-1 infection, regardless of the life stage. Our third main finding was the absence of genetic correlations between resistance to OsHV-1 infection and resistance to V. aestuarianus infection.
Selective breeding to enhance resistance to OsHV-1 infection could be achieved through selective breeding at early stages and would not affect resistance to V. aestuarianus infection. However, our results suggest that the potential to select for improved resistance to V. aestuarianus is lower. Selection for dual resistance to OsHV-1 and V. aestuarianus infection in C. gigas might reduce the impact of these two major diseases by selecting families that have the highest breeding values for resistance to both diseases.
在法国，两种主要疾病威胁着太平洋牡蛎的生产。自2008年以来，由于感染牡蛎疱疹病毒OsHV-1，太平洋牡蛎稚贝遭受了巨大损失，自2012年以来，商业规格的成年牡蛎大量死亡与河口弧菌感染有关。利用20个半同胞父系家系（每个家系包含两个全同胞家系），研究了对河口弧菌和OsHV-1的抗性遗传基础以及这两个性状之间的遗传相关性本质。对于每种疾病，使用3至26月龄的未感染过疾病的牡蛎进行受控感染挑战试验。此外，对同胞牡蛎在野外、池塘和水槽条件下进行测试，以确定实验室试验是否反映了牡蛎养殖业中发生的死亡事件。
首先，我们估计了太平洋牡蛎对河口弧菌的抗性遗传基础。稚贝期牡蛎对感染的易感性较低，但随着年龄增长易感性增加。其次，我们证实了早期对OsHV-1感染的抗性有很强的遗传基础，并表明后期也是如此。大多数家系从稚贝期到成年期对OsHV-1感染的抗性增强，而其他家系无论处于哪个生活阶段，与OsHV-1感染相关的死亡率始终较低或较高。我们的第三个主要发现是对OsHV-1感染的抗性与对河口弧菌感染的抗性之间不存在遗传相关性。
通过早期选择育种可以提高对OsHV-1感染的抗性，且不会影响对河口弧菌感染的抗性。然而，我们的结果表明，选择提高对河口弧菌抗性的潜力较低。在太平洋牡蛎中选择对OsHV-1和河口弧菌感染的双重抗性，可能通过选择对两种疾病抗性育种值最高的家系来降低这两种主要疾病的影响。
