【作者】 田华；

【导师】 邹桂伟；

【作者基本信息】 华中农业大学 ， 水产养殖， 2008， 硕士

【摘要】 鲢(Hypophthalmichthys molitrix C.et V)和鳙(Aristichthys nobilis Richardson)是我国重要的淡水经济鱼类,广泛分布于我国黑龙江、长江、和珠江流域,就养殖性能而言长江水系的两种鱼最好。近年来,由于长江受到日益增多的污染和大规模的水利建设等剧烈人类活动的影响,从而使长江水系鲢、鳙野生群体的种质资源受到严重干扰。在现有的养殖模式下,由于种种不科学的繁育,也造成养殖鲢、鳙的优良性状严重退化,如:生长缓慢、性成熟早、个体变小以及抗病力差等;再加上人工养殖群体同野生群体的混杂,以及生态环境的恶化,使鲢、鳙种质资源面临更加严重的威胁。因而,对长江水系鲢、鳙的遗传多样性进行研究,正确评估长江水系鲢、鳙野生群体与养殖群体种质资源现状以及它们之间存在的差异显得尤为必要。本研究采用本课题组与中国海洋大学共同开发的鲢微卫星引物中筛选出的22对用于长江水系野生鲢鳙(野生群体)和人工养殖鲢鳙(养殖群体)的遗传多样性分析,研究结果如下:(1)通过对长江野生鲢(Yangtze River wild silver carp,YSC)和养殖鲢(Domesticsilver carp,DSC)群体进行遗传参数统计,结果显示:在22个微卫星标记中,21个为多态标记,1个标记(BL12)在两个鲢群体中均为单态,多态位点百分率均为95.45%。22个微卫星标记在两个群体中共检测到等位基因188个,等位基因数在2～12之间变化。野生鲢和养殖鲢群体所观察微卫星位点的平均观测等位基因数分别为4.409和4.136(P＞0.05),平均有效等位基因数分别为3.276和3.034(P＞0.05),平均观测杂合度分别为0.744和0.693(P＞0.05),平均期望杂合度分别为0.612和0.581(P＞0.05),平均多态信息含量PIC分别为0.569和0.533(P＞0.05)。2个群体的平均Shannon’s指数分别为1.180和1.100(P＞0.05),群体间的遗传距离为0.280,两个群体间的遗传相似系数为0.756。所检测位点中,绝大多数位点的基因型都处于Hardy-Weinberg平衡状态,位点BL23在两个群体中均偏离平衡状态,BL90在野生群体中偏离平衡状态,在养殖群体中处于平衡状态;BL5和BL92在养殖群体中偏离平衡状态,在野生群体中处于平衡状态。固定指数Fst表明野生鲢与养殖鲢间7.67%的遗传多样性由群体间的遗传差异造成,大部分的遗传变异来自个体之间。通过研究发现,两个鲢群体都具有较高的遗传多样性,但野生鲢的遗传多样性较养殖鲢高,两者并未达到显著差异的水平(P＞0.05)。(2)通过对长江野生鳙(Yangtze River wild bighead carp,YBC)和养殖鳙(Domestic bighead carp,DBC)群体进行遗传参数统计,结果显示:在22个鲢微卫星标记中,19个为多态标记,3个标记(BL12、BL83和BL90)在两个鳙群体中均为单态,多态位点百分率均为86.36%。22个鲢微卫星标记在两个鳙群体中共检测到等位基因162个,等位基因数在2～12之间变化。野生鳙和养殖鳙群体所观察微卫星位点的平均观测等位基因数分别为3.727和3.636(P＞0.05),平均有效等位基因数分别为2.927和2.813(P＞0.05),平均观测杂合度分别为0.780和0.778(P＞0.05),平均期望杂合度分别为0.550和0.540(P＞0.05),平均多态信息含量PIC分别为0.500和0.487(P＞0.05)。2个群体的平均Shannon’s指数分别为1.020和0.986(P＞0.05),群体间的遗传距离为0.067,两个群体间的遗传相似系数为0.936。所检测位点中,绝大多数位点都处于Hardy-Weinberg平衡状态,在野生鳙群体中有1个位点(BL92)偏离平衡状态;在养殖鳙群体中有2个位点(BL82和BL8-1)偏离平衡状态。固定指数Fst表明野生鳙与养殖鳙之间2.64%的遗传多样性由群体间的遗传差异造成,这表明大部分的遗传变异来自个体之间。野生鳙群体只有1个位点杂合子缺失,在养殖鳙群体中所有位点均为杂合子过剩。选用的22对鲢微卫星引物,都能在鳙的两个群体中扩增出稳定的条带,可扩增比例为100%,其中86.36%表现多态性。两个鳙群体都具有丰富的遗传多样性,野生群体的略丰富于养殖群体,但差异并不显著(P＞0.05)。(3)利用微卫星分子标记对长江鲢鳙野生群体和养殖群体的研究发现,鲢、鳙野生和养殖群体均具有较高的遗传多样性。结果表明:虽然人类活动介入影响长江野生鲢鳙的生存环境,造成其生活环境的改变,致使繁殖群体变小,产卵场减少,对野生鲢鳙的遗传多样性有一定的影响,但在本试验中长江野生群体和养殖群体的遗传多样性并未出现明显的分化;本研究的鲢鳙养殖群体各只取了一个点的样,取样本身可能有一定的局限性,同时经历的人工选育周期比较短,因此养殖群体遗传多样性较野生群体没有显著差异。就目前来讲,鲢鳙野生和养殖群体都具有丰富的遗传多样性,均有较好的选育潜力,可以作为良好的育种材料进行鲢、鳙的本品种选育和新品种(系)培育,但在今后的利用和保护中应采取必要的措施来维持其遗传多样性。更多还原

【Abstract】 Silver carp(Hypophthalmichthys molitrix C.et V) and Bighead carp(Aristichthys nobilis Richardson) are important pond-cultured fish species in our country,and they inhabit widely in the major river basins of China,including Heilong Jiang,Yangtze River and Pearl River.Among the three local populations,the cultured performance of Yangtze River wild population is the best.In recent years,the germplasm of wild silver carp and bighead carp has been endangered by environmental pollution,large-scale water conservancy construction.Under present cultured operation,the germplasm of domestic silver carp and bighead carp was degenerated seriously due to various improper breeding methods.As a result,the elite characters of wild fish have been attenuated severely. Furthermore,germplasm of the two fish was much more seriously imperiled,as domestic population jumbles wild population and the depravation of ecologicial enviroment. Thereby,it’s particularly necessary to evaluate the genetic diversity and determine the genetic differentiation of silver carp and bighead carp.In this study,the genetic diversity of the two populations was studied using twenty-two microsatellite markers of silver carp designed by researchers in our research team and Ocean University of China.The results were as follows:(1) In the two silver carp populations,there was I monmorphic marker(BL12)in the two populations and the percentage of polymorphic loci was 95.45%.The total observed alleles number of the 22 microsatellite loci was 188,which varied from 2 to 12. The average of observed alleles number in the Yangtze River wild population and domestic population was 4.409 vs 4.136 respectively(P＞0.05);the average effective alleles number was 3.276 vs 3.034 respectively(P＞0.05);the average observed heterozygosity(Ho) was 0.744 vs 0.693 respectively(P＞0.05),and the average expected heterzygosity(He) was 0.612 vs 0.581 respectively(P＞0.05),and the average PIC was 0.569 vs 0.533 respectively(P＞0.05).The average Shannon’s index was 1.180 vs 1.100 respectively(P＞0.05);the genetic distance and the genetic similarity coefficient were 0.280 and 0.756 respectively.Chi-square test was used to analyze the genotypes based on Hardy-Weinberg equilibrium;the P value showed most loci tested were according with Hardy-Weinberg equilibrium.Fst index showed that most variation came from individuals within population(92.33%) rather than ones among populations(7.67%). The genetic diversity of domestic population was depressed to a certain extent,but there was no obvious difference between the two populations. (2) In the two bighead carp populations,there were 3 monmorphic markers (BL12,BL83 and BL90) in the two populations and the percentage of polymorphic loci was 86.36%.The total observed alleles number on the 22 microsatellite loci was 162, which varied from 2 to 12.The average of observed alleles number in the Yangtze River wild population and domestic population was 3.727 vs 3.636 respectively(P＞0.05);the average effective alleles number was 2.927 vs 2.813 respectively(P＞0.05);the average observed heterozygosity(Ho) was 0.780 vs 0.778 respectively(P＞0.05),and the average expected heterzygosity(He) was 0.550 vs 0.540 respectively(P＞0.05),and the average PIC was 0.500 vs 0.487 respectively(P＞0.05).The average Shannon’s index was 1.020 vs 0.986 respectively(P＞0.05);the genetic distance and the genetic similarity coefficient were 0.067 and 0.936 respectively.Chi-square test was used to analyze the genotypes based on Hardy-Weinberg equilibrium;the P value denoted that most loci tested were accorded with Hardy-Weinberg equilibrium.Fst index showed that most variation came from individuals within population(97.36%) rather than ones among populations (2.64%).One locus displayed lacking of heterozygote in the wild population,while all loci showed surplus heterozygote in the domestic population.These two populations were abundant in genetic diversity.(3) From the results of microsatellite markers analyzed,the wild population and domestic population of silver carp and bighead carp were both abundant in genetic diversity.The results showed that although artificial propagation process and human activity interference had changed the habitat,which caused the decrease in reproductive population and reduction in spawning stock and had influenced the genetic diversity of the two fish,the genetic diversity between the wild and domestic populations was no significant difference for the human’s interferences activities.From this research,the wild and the domestic population of silver carp and bighead carp were both abundant in genetic diversity and breeding potential.They can be as good breeding material to selected breed and cultivate new varieties(lines),domestic populations should adopt scientific selection and breeding measures to maintain genetic diversity.更多还原