Breeding for disease resistance of Penaeid shrimps
Breeding for disease resistance of Penaeid shrimps
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DOI：
10.1016/j.aquaculture.2008.09.011
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发表时间：
2009-01-07
期刊：
影响因子：
4.5
通讯作者：
Rye, Morten
中科院分区：
文献类型：
--
作者：
Cock, James;Gitterle, Thomas;Rye, Morten
疾病是对虾集约化生产的主要制约因素。生产池的条件有利于疾病的发展，发生了几种以前未报告的疾病的流行，造成了严重的损失。当消灭、根除或培养控制有困难时，选择性培育宿主对病原体的抗性可能是疾病控制的一个有吸引力的选择。然而，宿主耐药性不是万灵药，只有在以下情况下才应予以考虑：(a)疾病造成严重损害；(b)没有其他现有的简单、成本效益高的控制措施；(c)耐药性存在明显的遗传变异，且与其他理想特征没有过度的负相关。虾直到最近才被驯化，抗性育种直到20世纪90年代中期才开始；特别是虾类和甲壳类动物的养殖经验有限。因此，育种计划背后的原则和概念主要基于植物和动物王国中其他物种的经验。商业养殖户现在在池塘里播种对虾，选择抗陶拉综合征病毒的种群，取得了很好的结果，而到目前为止，开发抗白斑综合征病毒的种群一直是一个难以实现的目标。最初的TSV抗性种群是用简单的大规模选择技术培育出来的（哥伦比亚）。在后来的世代中，以家庭为基础的选择被应用于种群，最初的存活率约为30%，并小心地减少近亲繁殖和遗传变异的丧失。这表明，当原始种群具有合理的抗性水平，并且存在直接有效的选择协议时，培育抗性相对简单。对于灾难性疾病，如WSSV，可导致98%或以上的死亡率，耐药的频率很低，并且由于理论上的原因，有可能产生单基因而不是多基因的耐药。在育种群体中，抗性基因的低频率可能会造成遗传瓶颈，从而大大降低群体的遗传变异。为了保持遗传变异，应该将少数幸存者的基因渗入具有更广泛遗传变异的群体中。此外，为了最大限度地减少抗性破坏的可能性，在不同的位点上进行抗性基因的金字塔化是有利的。抗性的遗传变异可能在最初的基础种群中遇到，也可能由于突变或新的重组而自发产生。对于虾等极其多产的物种，可以很容易地筛选数百万动物的生存，因此可以确定耐药突变体或重组体。一旦发现了遗传变异，最适当的育种方法将取决于抗性和生产者感兴趣的疾病的性质。(c) 2008 Elsevier B.V.版权所有
Diseases are a major constraint on the intensive production of shrimps. Conditions in production ponds favour disease development, and epidemics of several previously unreported diseases have occurred and caused severe losses. When elimination, eradication or cultural control is difficult, selective breeding for host resistance to the pathogen may be an attractive option for disease control. However, host resistance is not a panacea and should only be considered when (a) the disease causes severe damage (b) there are no other existing simple cost effective control measures and (c) there is demonstrable genetic variation in resistance and this is not coupled with an excessive level of negative associations with other desirable characteristics. Shrimp have only recently been domesticated and breeding for resistance only began in the mid 1990s; there is limited experience with shrimp breeding in particular and crustaceans in general. Consequently, the principles and concepts behind breeding programmes are based largely on experiences with other species in both the plant and animal kingdoms. Commercial growers now seed ponds with shrimp populations selected for resistance to Taura Syndrome Virus with excellent results, whilst up to now development of White Spot Syndrome Virus resistant populations has been an elusive goal. The original TSV resistant populations were developed using simple mass selection techniques (Colombia). In later generations family based selection has been applied on populations, which initially had survival rates of about 30%, with care taken to reduce inbreeding and loss of genetic variation. This suggests that when the original populations have a reasonable level of resistance, and straightforward, effective selection protocols exist, it is relatively simple to breed for resistance. With catastrophic diseases, such as WSSV, which cause mortalities of 98% or more the frequency of resistance is low and it is suggested that for theoretical reasons single gene, rather than polygenic, resistance is likely to develop. The low frequency of resistance genes in breeding populations may cause genetic bottlenecks which will greatly reduce the genetic variation in the populations. In order to maintain the genetic variation the genes from the small numbers of survivors should be introgressed into populations with broader genetic variability. Furthermore, in order to minimize the probability of breakdown of resistance pyramiding of resistant genes on different loci would be advantageous.Genetic variation in resistance may be encountered either in the initial base populations or may spontaneously arise due to mutations or new recombinants. With extremely prolific species such as shrimps, millions of animals can readily be screened for survival and hence resistant mutants or recombinants may be identified. Once genetic variation has been detected the most appropriate breeding methodology will depend on the nature of both the resistance and the disease or diseases that are of interest to the producers. (c) 2008 Elsevier B.V. All rights reserved.