长牡蛎近交家系生物学特性及遗传多样性分析

发布时间：2018-07-03 10:26

本文选题：长牡蛎 + 近交　；参考：《中国海洋大学》2015年硕士论文

【摘要】：近交(inbreeding)指存在亲缘关系的个体间的交配。一方面随着近交代数的增加,近交可以加快一些控制优良性状的等位基因的纯合,加快育种进程；另一方面,近交也会使后代生长、存活等相关表型性状的指标降低,产生近交衰退。一直以来近交都是遗传育种以及生物多样性领域研究的热点问题。海洋双壳贝类由于具有高繁殖力、高的遗传变异水平以及多样的交配系统,已经成为研究近交及近交衰退的良好模式生物。长牡蛎(Crassostrea gigas)又称太平洋牡蛎,是世界上养殖范围最广、产量最大的海洋经济贝类,也是我国重要的传统养殖品种。近年来随着长牡蛎养殖规模的扩大,养殖群体内近交的现象时有发生,伴随出现死亡率高、经济性状衰退等问题,开展关于长牡蛎近交生物学及遗传多样性研究具有重要的理论和现实意义。本研究利用全同胞交配的方法,获得了连续2代的长牡蛎近交家系,研究了不同近交系数的长牡蛎家系在幼虫期和稚贝期产生的的近交效应,探讨了近交代数对长牡蛎不同生长阶段主要表型性状的影响。同时利用AFLP分子标记比较研究了长牡蛎一代全同胞交配家系F1、两代全同胞交配家系F2和野生对照家系的遗传多样性水平,探讨了近交对长牡蛎遗传多样性的影响。主要研究结果如下：1.长牡蛎近交家系生物学特性研究了对照家系(F=0)、F1家系(F=0.25)和F2家系(F=0.375)在孵化阶段的受精率与孵化率以及幼虫和稚贝阶段生长与存活等生物学特性。结果表明,各组的受精率均在90%以上,除F2组外其余2组的孵化率也在90%以上。幼虫阶段,近交组的壳高与壳长均从12日龄出现衰退,幼虫壳高的近交衰退程度随着近交系数的增加而加大；近交组存活率的衰退在整个幼虫阶段始终存在,且衰退程度随幼虫日龄的增加而加大。稚贝阶段,F1组和F2组的平均壳高在各日龄均出现近交衰退,且稚贝壳高的衰退程度也随着近交系数的增加而加大；3个实验组稚贝的平均壳长在60-240日龄无显著性差异(P0.05),直至300日龄近交组的平均壳长显著小于对照组,出现明显衰退；F1组和F2组稚贝存活率的衰退在不同日龄始终存在(IDC0),且随日龄的增加其衰退的程度逐渐地加大。研究表明近交对不同近交系数的长牡蛎家系影响不同,且不同性状的表现也不相同;长牡蛎虽经连续2代的全同胞交配,但部分性状衰退程度有增大趋势,没有获得具有优良等位基因的纯系后代,这也验证了长牡蛎具有较高遗传负荷的结论。因此有效淘汰长牡蛎群体中的遗传负荷(隐性有害等位基因)需要经过一段较长的近交历史,特别是一些在个体生长发育后期才表现出的危害程度较小的等位基因,它们并不会随着近交代数的增加而被轻易淘汰。2.长牡蛎近交家系遗传多样性研究利用9对AFLP引物对三个家系的遗传多样性进行了研究。结果显示,每对引物可产生14-35条清晰的扩增条带,9对引物在对照组、Fl组和F2组三个家系中扩增出的位点总数分别为215、204和200个,平均每对引物扩增的位点数为23.9、22.7和22.2个,其中有多态性的位点总数分别是67、58和55个,平均每对引物扩增的多态性位点数为7.4、6.4和6.1个,三个家系平均多态位点比例依次是31.16%、28.43%、27.5%；随着近交世代的增加,由Shannon多样性指数和Nei's基因多样性指数反映的长牡蛎近交家系遗传多样性水平有降低的趋势。研究表明长牡蛎具有较高遗传变异水平,同时近交可使其遗传多样性水平下降,本研究为长牡蛎近交家系选择育种和遗传改良提供了重要参考资料。
[Abstract]:Inbreeding (inbreeding) refers to the mating among individuals with relatives. On the one hand, with the increase of inbreeding algebra, inbreeding can accelerate the homozygosity of some alleles that control excellent traits and accelerate the breeding process; on the other hand, inbreeding will also make offspring growth, survival and other related phenotypic traits decrease and produce inbreeding decline. Inbreeding is a hot issue in the field of genetic breeding and biodiversity. The marine bivalve has become a good model for the study of inbreeding and inbreeding because of its high fecundity, high genetic variation and multiple mating systems. The Crassostrea gigas is also known as the Pacific oyster. The most widely cultivated and most productive marine economy shellfish is an important traditional breed in China. In recent years, with the enlargement of the size of the long oyster culture, the phenomenon of inbreeding in the aquaculture population is occurring, with the high mortality rate and the decline of the economic characters, the study on the biologic and genetic diversity of oysters has been carried out. Important theoretical and practical significance. In this study, full sib mating method was used to obtain 2 generations of long oyster inbred lines, and the inbreeding effect on the larval and juvenile stages of oyster families with different inbreeding coefficients was studied, and the effects of inbreeding algebra on the main phenotypic characters of different growth stages of oysters were discussed. AFLP molecular markers were used to compare the genetic diversity of the two generation full sib mating family F1, the two generation full sib mating family and the wild control family. The effects of inbreeding on the genetic diversity of oysters were investigated. The main results were as follows: the biological characteristics of the 1. long oysters in the inbred lines were studied in the control family (F=0), the F1 family The fertilization rate and hatchability of the F=0.25 and F2 family (F=0.375) at the hatching stage, and the biological characteristics of the growth and survival of the larvae and juvenile stages. The results showed that the fertilization rate of each group was above 90%, and the hatching rate of the other 2 groups except the F2 group was over 90%. The shell height and shell length of the inbred group declined from 12 days of age. The degree of inbreeding decline with the increase of inbreeding coefficient increased with the increase of inbreeding coefficient, and the survival rate of the inbreeding group existed throughout the larval stage, and the decline degree increased with the increase of the larval age. The average shell height of the F1 and F2 groups appeared close and declines at every day of age, and the decline degree of the shell high was also inbred. The average shell length of juvenile shellfish in the 3 experimental groups had no significant difference (P0.05) at the age of 60-240 days. The average shell length of the 300 day age group was significantly smaller than that of the control group, and the survival rate of the juvenile shellfish in the F1 group and F2 group remained at the age of different days (IDC0). The study showed that the effects of inbreeding on the family of oyster families with different inbreeding coefficients were different, and the performance of different characters was different. Although the long oysters were copulated by 2 successive generations, the decline degree of some characters increased and the pure lineage with good alleles was not obtained. It also proved that long oysters had higher remains. Therefore, the effective elimination of the genetic load (recessive harmful allele) in the oyster population requires a long history of inbreeding, especially some alleles that are less harmful in the late stage of growth and development, and they do not easily eliminate.2. long oysters with the increase of inbreeding algebra. Genetic diversity in the genetic diversity of the inbred lines was studied using 9 pairs of AFLP primers to study the genetic diversity of three families. The results showed that 14-35 pairs of amplified bands could be produced per pair of primers, 9 pairs of primers in the control group, the Fl group and the F2 group were 215204 and 200, respectively, and the average number of primers per pair of primers was amplified. The number of points was 23.9,22.7 and 22.2, of which the total number of polymorphic loci was 67,58 and 55 respectively. The average number of polymorphic locations per pair of primers was 7.4,6.4 and 6.1, and the proportion of average polymorphic loci in three families was 31.16%, 28.43%, 27.5%. With the increase of inbred generations, the Shannon diversity index and the Nei's gene diversity index were increased. The study shows that the genetic diversity of oysters in oysters has a tendency to decrease. The study shows that the oyster has a high level of genetic variation, and the inbreeding can reduce the genetic diversity. This study provides important reference data for selection breeding and genetic improvement of oysters.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S917.4

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