Perspectives from agriculture: advances in livestock breeding - implications for aquaculture genetics

In this paper we present livestock breeding developments that could be taken into consideration in the genetic improvement of farmed aquaculture species, especially in freshwater fish. Firstly, the current breeding objective in aquatic species has focused almost exclusively on the improvement of body weight at harvest or on growth related traits. This is unlikely to be sufficient to meet the future needs of the aquaculture industry. To meet future demands breeding programs will most likely have to include additional traits, such as fitness related ones (survival, disease resistance), feed efficiency, or flesh quality, rather than only growth performance. In order to select for a multi-trait breeding objective, genetic variation in traits of interest and the genetic relationships among them need to be estimated. In addition, economic values for these traits will be required. Generally, there is a paucity of data on variable and fixed production costs in aquaculture, and this could be a major constraint in the further expansion of the breeding objectives. Secondly, genetic evaluation systems using the restricted maximum likelihood method (REML) and best linear unbiased prediction (BLUP) in a framework of mixed model methodology could be widely adopted to replace the more commonly used method of mass selection based on phenotypic performance. The BLUP method increases the accuracy of selection and also allows the management of inbreeding and estimation of genetic trends. BLUP is an improvement over the classic selection index approach, which was used in the success story of the genetically improved farmed tilapia (GIFT) in the Philippines, with genetic gains from 10 to 20 per cent per generation of selection. In parallel with BLUP, optimal genetic contribution theory can be applied to maximize genetic gain while constraining inbreeding in the long run in selection programs. Thirdly, by using advanced statistical methods, genetic selection can be carried out not only at the nucleus level but also in lower tiers of the pyramid breeding structure. Large scale across population genetic evaluation through genetic connectedness using cryopreserved sperm enables the comparison and ranking of genetic merit of all animals across populations, countries or years, and thus the genetically superior brood stock can be identified and widely used and exchanged to increase the rate of genetic progress in the population as a whole. It is concluded that sound genetic programs need to be established for aquaculture species. In addition to being very effective, fully pedigreed breeding programs would also enable the exploration of possibilities of integrating molecular markers (e.g., genetic tagging using DNA fingerprinting, marker (gene) assisted selection) and reproductive technologies such as in-vitro fertilization using cryopreserved spermatozoa.

Progress toward a global genealogy of common carp (Cyprinus carpio L.) strains using mitochondrial nucleotide sequences data

As part of a study of genetic variation in the Vietnamese strains of the common carp (Cyprinus carpio L.) using direct DNA sequencing of mitochondrial control and ATPase6/8 gene regions, samples from a number of other countries were analyzed for comparison. Results show that the levels of sequence divergence in common carp is low on a global scale, with the Asian carp having the highest diversity while Koi and European carp are invariant. A genealogical analysis supports a close relationship among Vietnamese, Koi, Chinese Color and, to a lesser extent, European carp. Koi carp appear to have originated from a strain of Chinese red carp. There is considerable scope to extend this research through the analysis of additional samples of carp from around the world, especially from China, in order to generate a comprehensive global genealogy of common carp strains.

中国三种野生稻的遗传变异与保护生物学研究

稻属(OryzaL．)隶属禾本科(Poaceae)之稻族(OryzeaeDUmort.)，广布于全球热带与亚热带地区。目前认为该属约含20个野生种和2个栽培种，中国产4个种。亚洲栽培稻(O. sativaL．)是世界上最重要的粮食作物之一，而在中国则为第一粮食作物。在稻种基因库中，发掘野生稻中丰富的遗传多样性是解决当今人口与粮食矛盾的必由之路。因此，保护野生稻的遗传多样性举世瞩目。针对热带与亚热带地区的环境恶化而导致野生稻居群的大量绝灭与急剧萎缩的状况，制订有效的策略，最大限度地保护野生稻的遗传多样性已迫在眉睫。然而，目前对野生稻种内遗传多样性的知识十分贫乏，缺乏制订保护策略的科学基础。这一问题在中国尤为突出。本文基于1994-1995年对中国三种野生稻濒危状况的调查结果，利用等位酶分析对普通野生稻26个居群，药用野生稻8个居群和疣粒野生稻l7个居群进行了遗传多样性的研究，并重点对目前育种价值最大而濒危程度最高的普通野生稻从五个方面作了进一步的探讨。最后根据遗传多样性的研究结果讨论了它们的濒危原因，并提出了初步的保护策略。主要结果如下： 一．普通野生稻D．rufipogon Griff. 在中国的三种野生稻中，普通野生稻的遗传多样性水平最高(A=1.33，P= 0.227，Ho=0.033和He=_0.068)，遗传分化水平较低(Fst=0,310)。广西与广东的居群较其它地区的居群具有较丰富的遗传变异。因此，华南可能是中国普通野生稻的遗传多样性中心;云南现存的所有三个居群的遗传多样性水平偏低(A=1.10.p=0.148，Ho=0.007和He=0.079)，与该地区栽培稻丰富的遗传多样性形成鲜明对照，普通野生稻居群间的遗传一致度与地理距离无明显相关。 1．通过14个中央居群与5个边缘居群的对比研究表明了边缘居群的遗传结构明显不同于中央居群：其遗传多样性水平与遗传分化均低予中央居群，杂合子比中央居群更为不足。而且，从中央居群到边缘居群，位点的多态性逐渐丧失，遗传多样性水平递减，一些多态位点的等位基因频率逐渐地发生变化。 2. 通过7个受栽培稻基因渗入的居群与5个隔离较好居群的对比研究表明，被渗入居群虽然在形态上表现出复杂的变异式样，但遗传多样性水平并无相应的增高。栽培稻基因流对野生居群遗传结构的影响可能主要是遗传同化，即阻止其居群内与居群间的遗传分化。 3. 通过对2个低纬度居群与2个北缘居群两个生活史阶段的遗传多样性研究表明繁育系统是影响普通野生稻居群遗传结构的因素之一。在低纬度居群中种子阶段的遗传变异高于植株阶段，在高纬度居群中则相反。 4．通过对北缘居群(江西东乡)1980年，1985年和1994年的居群遗传结构的研究，发现该居群的遗传结构逐渐在发生变化，表现为遗传多样性水平不断下降，居群越来越偏移哈迪一温伯格平衡和杂合子变得越来越缺乏。 5．通过对一个典型的普通野生稻居群（元江居群）的居群内遗传结构的研究，表明遗传变异在3个亚居群间分布不均衡，基因型里聚集分布，使得亚居群间有一定的遗传分化。导致其居群遗传结构的亚划分的主要原因可能是有限的基因流(Nm=0.964

稀有植物太行花的保护生物学研究

悬崖代表着一个残遗的、较少受到干扰的古生境，悬崖也是生物多样性的避难所。这个特殊生境中分布种类丰富的稀有植物和特有植物，而这些稀有和特有植物又往往以悬崖为唯一的生境，在长期的演化历史进程中形成彼此相互适应的关系。这种分布在特殊生境中的稀有植物为保护研究提出了新的研究方向和问题。本文以蔷薇科的中国特有植物太行花（Taihangia rupestris Yü et Li）为对象，对这个仅分布在有限的地理范围内悬崖上的稀有物种进行了保护生物学的研究。 利用RAPD分子标记技术对太行花8个居群的遗传多样性和遗传结构进行了检测分析。结果表明太行花居群内维持着较高的遗传多样性水平，未显示遭受过严重遗传瓶颈的迹象。同时，居群间遗传分化显著，与居群间的地理距离相关，聚类分析得到的树系图与太行花种下两个变种（太行花原变种Taihangia rupestris var. rupestris和缘毛太行花Taihangia rupestris var. ciliate Yü et Li）的划分相符。 通过栽培实验，研究了太行花对光照和养分的反应，从生态学角度检测植物对环境因子变化的适应能力。结果表明光照处理显著影响太行花的气体交换参数，且显示出随季节不同而变化的趋势。在8月第一次测量时，光合速率随着光照水平的增加而增加;而在9月底第二次测量时，高光下植株的光合速率反低于中光条件下的植株。光合光反应曲线表明太行花对不同光照水平（高光、中光和低光）均显示出一定的光合适应性。 光照对太行花的生长反应、形态、解剖等指标均具有显著的作用。在收获时，高光下植物形成小而厚的叶片，更快的叶片形成速率足以弥补单叶面积上光合速率的下降，使植株维持最大的总生物量。中光条件下的植株具有更长的叶柄，更大的叶面积，大而薄的叶片，和更大的叶面积比，被认为是对较弱光照环境适应的表现。而光照对叶片的气孔指标（气孔密度、气孔指数和大小）没有作用，养分施加对太行花的影响也甚微。总体来说，太行花显示出对光照变化的生理适应性和形态可塑性，光照和养分这两个环境条件均非影响太行花局限分布的关键因素。 同时，我们采用扫描电镜手段跟踪观察了太行花的花的早期发育过程。太行花早期发育过程中苞片内残留的退化花痕迹表明，太行花的顶生单花其实是有限聚伞花序中其它花芽败育的结果，显示出从花序向单花演化的趋势。同时，雌蕊的发育在早期是正常的，未显示出退化痕迹。 根据以上结果表明，局限分布在特殊生境上的太行花并未显示出生理适应幅度的狭窄性和遗传多样性水平的降低，因此，太行花在长期的进化过程中形成了对特殊生境——悬崖的适应性，遗传衰退和缺乏适应性不是稀有植物太行花局限分布的原因。在对太行花的保护中应进一步加强对其生境的保护，并在进行迁地保护和回归引种时应兼顾不同变种和地理分布的居群，以实现对其遗传完整性的有效保护。

长花马先蒿的居群遗传变异与生物地理学

青藏高原地区是我国植物物种多样性和特有性最高的地区，且作为东亚植物区系的一个现代分化中心受世人瞩目。长花马先蒿是青藏高原高山草甸的广布种，其地理分布格局的形成与高原的隆升和气候变迁有着密切关系。因此，对长花马先蒿进行谱系生物地理学研究，有助于探讨青藏高原地区物种快速分化的机制和群体建立过程。 本研究对长花马先蒿11个居群、188个个体的叶绿体DNA trnT-trnF区进行了序列分析，发现该片段的长度变异范围为1441-1472bp。对位排列后的矩阵（含外类群）长1534bp，内类群中含33个碱基替换和 17 个插入/缺失,可分为20种单倍型。11个地理居群的总核苷酸多态性（π）为0.00468，单倍型多态性（Hd）为0.853，居群间的遗传变异（FST）高达88.2％，说明长花马先蒿具有很高的遗传多样性，且居群间发生了强烈遗传分化。 系统发育和遗传多样性分析发现长花马先蒿的20种叶绿体单倍型可归于四个地理单元——川西高海拔地区、川北地区、云南德钦地区及川藏地区。进一步分析发现：4个地理单元间存在着显著的遗传分化, 说明长花马先蒿具有明显的谱系地理分布格局。其中川西高海拔地区的四种主导单倍型构成了系统发育树最基部的一支，而以川西地区为中心、向南扩展至云南的两个居群所包含的几种单倍型均属于比较进化的类型。单倍型的网络关系(Network) 显示出西藏、青海、云南及四川北部的一些单倍型间遗传差异很小，亲缘关系很近。上述结果表明：长花马先蒿群体在冰期后的重新扩张过程主要表现为由南往北的递进式扩散，第四纪冰期气候的反复波动导致了该物种居群随生境变化而不断扩张或收缩,形成了现今的分布格局。初步推测川西地区很可能曾是长花马先蒿在第四纪冰期时的重要避难所，瓶颈效应和奠基者效应对其遗传多样性分布格局有重要影响。

藏麻黄与丽江麻黄的形态及遗传变异研究

麻黄属(Ephedra)起源较早，该属植物的形态性状极度退化或简化，可用于经典分类学的有价值的性状非常有限。分布于青藏高原的藏麻黄（E. saxatilis）和丽江麻黄（E. likiangensis）二者间形态相似，性状变异连续，很难分辨，但被《中国植物志》中、英文版作两个种处理。 本文对藏麻黄和丽江麻黄的七个居群、151个个体的叶、雌球花和节间长等形态学性状进行了分析，发现各性状的变异情况在群体间无明显差异。同时我们还对154个个体的叶绿体DNA trnT-trnF和 trnS-trnfM区进行了序列分析，两个片段的联合矩阵长1382bp，共有29个变异位点，其中有9个碱基变异和2个indel，可划分为H1、H2和H3三种单倍型。这3种单倍型在丽江麻黄中均有分布，但藏麻黄仅含H1和H2。 综合来自形态学和分子方面的证据，我们发现藏麻黄和丽江麻黄的关系非常近缘，因此建议予以合并。同时本文还以膜果麻黄（E. przewalskii）为外类群，从谱系生物地理学角度探讨了三种叶绿体单倍型的进化关系，发现H2最原始，分布最广;H1与其它两种单倍型间的序列差异较大，可能是较进化的类型。此外，无性克隆的繁殖方式可能是导致Ephedra单倍型非常简单的重要原因之一。

苍山冷杉复合体的居群遗传变异与谱系地理学

青藏高原为冷杉属(Abies)的多度中心，共分布有10种，9变种和4亚种。其中苍山冷杉复合体(Abies delavayi complex)包括3种，5变种和2亚种。它们的形态性状变异较小，且分布区重叠。迄今对该复合体的遗传多样性水平、分化程度以及进化历史仍缺乏了解。 本研究对苍山冷杉复合体的14个居群、302个个体进行取样，并对193个个体的母系遗传线粒体DNA nad1 intron2区和276个个体的父系遗传的叶绿体DNA trnS-trnG区进行了序列分析。该复合体的线粒体DNA nad1 intron2区的序列为675bp，其中有4个单碱基变异和1个插入/缺失，可分为6种线粒体单倍型。这14个居群的线粒体总核苷酸多态性(π)为0.00114，单倍型多态性(Hd)为0.627，居群间的遗传变异(FST)高达84.034%。叶绿体DNA trnS-trnG区的序列排列后为718bp，共有8个单碱基变异和4个插入/缺失，可分为12种叶绿体单倍型。这14个居群的总核苷酸多态性(π)为0.00116，单倍型多态性(Hd)为0.590，居群间的遗传变异(FST)为65.830%。以上结果显示苍山冷杉复合体居群间已经产生了强烈的遗传分化。叶绿体的3种主导单倍型(H1、H2和 H3)在YLXS、SKXS、GS和WX 4个居群中都有分布;而其它居群则只有主导单倍型(除SJLS外)中的1种或2种。造成边缘居群(如JZS)多样性较低的主要原因是冰期后群体在迁移过程中的遗传漂变和奠基者效应。根据谱系关系线粒体H1型和叶绿体H3型均为较古老的单倍型，线粒体和叶绿体的谱系关系均支持上述分析。 本研究初步推测青藏高原的东南部—横断山区(包括YLXS、SKXS、GS、WX、BMXS、ELS和EMS)可能为苍山冷杉复合体的冰期避难所，群体存在冰期后向西和向南扩张的过程。间冰期群体隔离和扩张过程中的奠基者效应是形成目前居群分化和遗传多样性分布格局的重要因素。

An environmentally based growth model that uses finite difference calculus with maximum likelihood method: its application to the brackish water bivalve Corbicula japonica in Lake Abashiri, Japan

We present a growth analysis model that combines large amounts of environmental data with limited amounts of biological data and apply it to Corbicula japonica. The model uses the maximum-likelihood method with the Akaike information criterion, which provides an objective criterion for model selection. An adequate distribution for describing a single cohort is selected from available probability density functions, which are expressed by location and scale parameters. Daily relative increase rates of the location parameter are expressed by a multivariate logistic function with environmental factors for each day and categorical variables indicating animal ages as independent variables. Daily relative increase rates of the scale parameter are expressed by an equation describing the relationship with the daily relative increase rate of the location parameter. Corbicula japonica grows to a modal shell length of 0.7 mm during the first year in Lake Abashiri. Compared with the attain-able maximum size of about 30 mm, the growth of juveniles is extremely slow because their growth is less susceptible to environmental factors until the second winter. The extremely slow growth in Lake Abashiri could be a geographical genetic variation within C. japonica.

The geographic basis for population structure in Fraser River chinook salmon (Oncorhynchus tshawytscha)

We surveyed variation at 13 microsatellite loci in approximately 7400 chinook salmon sampled from 52 spawning sites in the Fraser River drainage during 1988–98 to examine the spatial and temporal basis of population structure in the watershed. Genetically discrete chinook salmon populations were associated with almost all spawning sites, although gene flow within some tributaries prevented or limited differentiation among spawning groups. The mean FST value over 52 samples and 13 loci surveyed was 0.039. Geographic structuring of populations was apparent: distinct groups were identified in the upper, middle, and lower Fraser River regions, and the north, south, and lower Thompson River regions. The geographically and temporally isolated Birkenhead River population of the lower Fraser region was sufficiently genetically distinctive to be treated as a separate region in a hierarchial analysis of gene diversity. Approximately 95% of genetic variation was contained within populations, and the remainder was accounted for by differentiation among regions (3.1%), among populations within regions (1.3%), and among years within populations (0.5%).Analysis of allelic diversity and private alleles did not support the suggestion that genetically distinctive populations of chinook salmon in the south Thompson were the result of postglacial hybridization of ocean-type and stream-type chinook in the Fraser River drainage. However, the relatively small amount of differentiation among Fraser River chinook salmon populations supports the suggestion that gene flow among genetically distinct groups of postglacial colonizing groups of chinook salmon has occurred, possibly prior to colonization of the Fraser River drainage.

Hybridization between two serranids, the coney (Cephalopholis fulva) and the creole-fish (Paranthias furcifer), at Bermuda

Intergeneric hybridization between the epinepheline serranids Cephalopholis fulva and Paranthias furcifer in waters off Bermuda was investigated by using morphological and molecular characters. Putative hybrids, as well as members of each presumed parent species, were analyzed for 44 morphological characters and screened for genetic variation at 16 nuclear allozyme loci, two nuclear (n)DNA loci, and three mitochondrial (mt)DNA gene regions. Four of 16 allozyme loci, creatine kinase (CK-B*), fumarase (FH*), isocitrate dehydrogenase (ICDH-S*), and lactate dehydrogenase (LDH-B*), were unique in C. fulva and P. furcifer. Restriction fragments of two nuclear DNA intron regions, an actin gene intron and the second intron in the S7 ribosomal protein gene, also exhibited consistent differences between the two presumed parent species. Restriction fragments of three mtDNA regions—ND4, ATPase 6, and 12S/16S ribosomal RNA—were analyzed to identify maternal parentage of putative hybrids. Both morphological data and nuclear genetic data were found to be consistent with the hypothesis that the putative hybrids were the result of interbreeding between C. fulva and P. furcifer. Mean values of 38 morphological characters were different between presumed parent species, and putative hybrids were intermediate to presumed parent species for 33 of these characters. A principal component analysis of the morphological and meristic data was also consistent with hybridization between C. fulva and P. furcifer. Thirteen of 15 putative hybrids were heterozygous at all diagnostic nuclear loci, consistent with F1 hybrids. Two putative hybrids were identified as post-F1 hybrids based on homozygosity at one nuclear locus each. Mitochondrial DNA analysis showed that the maternal parent of all putative hybrid individuals was C. fulva. A survey of nuclear and mitochondrial loci of 57 C. fulva and 37 P. furcifer from Bermuda revealed no evidence of introgression between the parent species mediated by hybridization.

入侵植物紫茎泽兰遗传变异及克隆多样性研究

现存植被与其花粉分布的关系可作为利用化石花粉图谱重建古植被时的参照，因此，理解现存表土花粉分布格局对解释花粉图谱十分关键。提高花粉鉴定精度是孢粉学和古生态学家一直努力想要解决的关键问题。目前的孢粉学方法将表土花粉鉴定到属的水平都十分困难，因此造成依据花粉图谱进行植被重建的时候出现无法矫正的误差。本研究用分子生物学方法将藜科植物表土花粉鉴定精度从科的水平提高到种的水平。表土花粉样品取自新疆中部样带，利用样带内所有出现的藜科植物共19个种建立藜科植物核基因内转录间隔1区（ITS1）序列库，然后通过巢式聚合酶链式反应（PCR）进行单粒表土花粉的ITS1序列扩增和测序，与序列库中的序列进行比对，从而确定单粒花粉来自哪种藜科植物。这种相对简单的以PCR为基础的方法可以将表土花粉鉴定到种，使在种的水平解释植被与花粉分布的关系成为可能。 紫茎泽兰（Eupatorium adenophorum）是广泛分布在中国西南的入侵植物。以无融合生殖为主，其压条性克隆繁殖方式经常被忽视，本文以紫茎泽兰为例，研究无融合生殖和压条性克隆繁殖为主的入侵种群遗传变异与克隆多样性，分析无融合生殖入侵种群具有高度竞争力和适应能力的分子机制。实验用AFLP分子标记检测了包括缅甸一个种群在内的17个种群的基因组多样性，结果表明，紫茎泽兰是多克隆植物，有丰富的基因型数量，遗传多样性水平低（He＝0.0439），大部分（73.59%）遗传变异存在于种群内，种群间存在显著遗传分化。紫茎泽兰克隆生长策略为游击型，倒伏性克隆繁殖有助于小范围内种群的扩张。各种群基因型组成存在很大差异，但基因型间相似性很高，有相当多的基因型可能来自遗传重组。紫茎泽兰的有性繁殖比例可能比以往所推测的高得多，有助于保持基因型的多样性。

Mitochondrial diversity and phylogeographic structure of Chinese domestic goats

China has numerous native domestic goat breeds, but so far there has been no extensive study on genetic diversity, population demographic history, and origin of Chinese goats. Here, we examined the genetic diversity and phylogeographic structure of Chinese domestic goats by determining a 481-bp fragment of the first hypervariable region of mitochondrial DNA (mtDNA) control region from 368 individuals representing 18 indigenous breeds. Phylogenetic analyses revealed that there were four mtDNA lineages (A-D) identified in Chinese goats, in which lineage A was predominant, lineage B was moderate, and lineages C and D were at low frequency. These results further support the multiple maternal origins of domestic goats. The pattern of genetic variation in goat mtDNA sequences indicated that the two larger lineages A and B had undergone population expansion events. In a combined analysis of previously reported sequences and our sequences belonging to lineage B, we detected two subclades, in which one was unique to eastern Asia and another was shared between eastern and southern Asia. A larger genetic variation in eastern Asia than southern Asia and the pattern of phylogeographic variation in lineage B suggest that at least one subclade of lineage B originated from eastern Asia. There was no significant geographical structuring in Chinese goat populations, which suggested that there existed strong gene flow among goat populations caused by extensive transportation of goats in history. (c) 2005 Elsevier Inc. All rights reserved.

Differential population structuring and demographic history of two closely related fish species, Japanese sea bass (Lateolabrax japonicus) and spotted sea bass (Lateolabrax maculatus) in Northwestern Pacific

The Quaternary cold periods in the Northwestern Pacific are thought to have heavily influenced the amount and distribution of intraspecific genetic variation in marine fishes. To estimate the demographic history and genetic structure of Lateolabrax macula

Molecular phylogeography and population structure of a mid-elevation montane frog Leptobrachium ailaonicum in a fragmented habitat of southwest China

Leptobrachium ailaonicum is a vulnerable anuran restricted to a patchy distribution associated with small mountain streams surrounded by forested slopes at mid-elevations (approximately 2000-2600 m) in the subtropical Mount Wuliang and Mount Ailao ranges in southwest China (Yunnan Province) and northern Vietnam. Given high habitat specificity and lack of suitable habitat in lower elevations between these ranges, we hypothesized limited gene flow between populations throughout its range. We used two mitochondrial genes to construct a phylogeographic pattern within this species in order to test our hypothesis. We also examined whether this phylogeographic pattern is a response to past geological events and/or climatic oscillations. A total of 1989 base pairs were obtained from 81 individuals of nine populations yielding 51 unique haplotypes. Both Bayesian and maximum parsimony phylogenetic analyses revealed four deeply divergent and reciprocally monophyletic mtDNA lineages that approximately correspond to four geographical regions separated by deep river valleys. These results suggest a long history of allopatric separation by vicariance. The distinct geographic distributions of four major clades and the estimated divergence time suggest spatial and temporal separations that coincide with climatic and paleogeographic changes following the orogeny and uplift of Mount Ailao during the late Miocene to mid Pliocene in southwest China. At the southern distribution, the presence of two sympatric yet differentiated clades in two areas are interpreted as a result of secondary contact between previously allopatric populations during cooler Pleistocene glacial cycles. Analysis of molecular variance indicates that most of the observed genetic variation occurs among the four regions implying long-term interruption of maternal gene flow, suggesting that L ailaonicum may represent more than one distinct species and should at least be separated into four management units corresponding to these four geographic lineages for conservation. (C) 2009 Elsevier Inc. All rights reserved.

草鱼野生和养殖群体间遗传变异的微卫星分析

运用微卫星标记对江苏境内草鱼(Ctenopharyngodon idella)一个野生群体(邗江群体)和两个养殖群体(淡水中心群体和无锡前洲群体)遗传多样性进行了分析.在10个座位中,每个座位检测到的等位基因数2～8个.有效等位基因数、多态信息含量、期望杂合度、平均表观杂合度均以邗江草鱼野生群体最高,分别为3.9、0.506 8、0.693 9、0.7;无锡前洲草鱼养殖群体最低,分别为2.2、0.179 6、0.523 5、0.528 6;淡水中心草鱼养殖群体各参数均介于两者之间,分别为3.5、0.290 2、0.541 8、0.542 9.以上结果表明:草鱼野生群体遗传多样性更为丰富,而草鱼养殖群体存在杂合度降低,遗传多样性下降的现象.邗江草鱼野生群体与淡水中心草鱼养殖群体和无锡前洲草鱼养殖群体间遗传分化系数分别为0.219和0.246,而两个草鱼养殖群体间遗传分化系数为0.034.这表明草鱼野生群体与草鱼养殖群体间分化严重,而草鱼养殖群体间分化微弱.各座位分化程度的χ2检验结果表明,10个座位中有GM18、MFW1-1、MFW1-2三个座位群体间分化达到极显著水平,GM03-2、MFW5两个座位群体间分化差异显著,其他座位分化不显著.针对每个座位对各群体进行Hardy-Weinberg平衡检验发现:由于草鱼养殖群体在GM03-1、GM03-2、GM18三个位点杂合子缺失,草鱼野生群体在位点GM19杂合子过剩而严重偏离平衡.实验表明:近交容易引起草鱼遗传多样性下降,纯合速度加快.