基于SCoT分子标记的黄河鲤抗嗜水气单胞菌不同群体遗传多样性分析

Genetic diversity analysis of different populations of Cyprinus carpio resistant to Aeromonas hydrophila based on SCoT molecular markers

  • 摘要: 【目的】基于SCoT分子标记探讨黄河鲤遗传多样性与其抗嗜水气单胞菌能力的关系,为黄河鲤的抗病育种提供理论依据。【方法】通过腹腔注射对300尾黄河鲤进行人工感染嗜水气单胞菌,按死亡顺序分为最先死亡群体(FP)、最后死亡群体(LP)和存活群体(SP),每个群体选取30尾。从80条SCoT引物中筛选出多态性好、重复性高、条带清晰的引物,对3个黄河鲤群体进行多态性扩增,采用PopGene32和Arlequin 3.5计算3个群体的等位基因数(Na)、有效等位基因数(Ne)、Nei’s基因多样性指数(H)及Shannon’s信息指数(I)等遗传参数,基于Nei’s遗传距离(Ds)利用MEGA 7.0中的非加权组平均法(UPGMA)构建系统发育进化树,并以Structure 2.3进行群体间的遗传结构分析。【结果】黄河鲤感染嗜水气单胞菌的死亡率为40.0%。从80条SCoT引物中筛选出18条扩增条带清晰、多态性好的引物,从3个黄河鲤群体中共扩增出103条条带,其中多态性条带97条,占94.17%。3个黄河鲤群体的Na范围为1.7961~1.8155,Ne范围为1.3828~1.4029,H范围为0.2258~0.2467,I范围为0.3453~0.3804;群体间的遗传分化指数(Gst)为0.0972,即90.28%的遗传多样性分布在群体内部。3个黄河鲤群体的遗传分化指数(Fst)为0.1299,属于轻度遗传分化;群体间的Ds分布在0.0248~0.0835,其中FP群体与SP群体的遗传距离最大。基于Ds的UPGMA聚类分析结果显示,FP群体和LP群体聚为一支,SP群体单独聚为一支;遗传结构分析结果表明,3个黄河鲤群体可分为2个亚群[抗病群体(SP)和易感群体(FP和LP)]。可见,通过黄河鲤死亡时间划分的群体与通过聚类分析及遗传结构分析得出的群体基本一致。【结论】黄河鲤抗嗜水气单胞菌的能力随着群体遗传多样性的增大而增强。因此,在黄河鲤抗病品种(系)选育过程中应保证足够的群体数量,在提高生长、营养等经济性状的同时保证一定的基因杂合度。

     

    Abstract: 【Objective】 To explore the relationship between genetic diversity and resistance to AeromonA. hydrophila in Yellow River carp(Cyprinus carpio) based on SCoT molecular markers, so as to provide a theoretical basis for breeding for disease-resistant in C. carpio.【Method】 300 C. carpio were infected with A. hydrophila through intraperitoneal injection, and divided into the first dead population(FP), the last dead population(LP) and the surviving population(SP) according to the time order of mortality, with 30 carps selected from each population. The primers with high polymorphism, high repeatability and clear bands were screened from 80 SCoT primers to conduct polymorphic amplification for the 3 populations of C. carpio. The number of alleles(Na), effective alleles(Ne), Nei's gene diversity index(H) and Shannon's diversity index(I) of the 3 populations were calculated by PopGene32 and Arlequin 3.1. Phylogenetic trees were constructed based on Nei's genetic distance(Ds) using unweighted group average(UPGMA) in MEGA 7.0, and Structure 2.3 was used to analyze the genetic structure among populations.【Result】 C. carpio mortality rate infected with A. hydrophila was 40%. 18 primers with clear bands and high polymorphism were screened from 80 SCoT primers, and polymorphism from the 3 C. carpio populations. 97 polymorphic bands accounted for 94.17% of the total bands. Na ranged from 1.7961 to 1.8155, Ne ranged from 1.3828 to 1.4029, H ranged from 0.2258 to 0.2467, and I ranged from 0.3453 to 0.3804 for the 3 C. carpio populations. The genetic differentiation index(Gst) between populations was 0.0972, indicating that 90.28% of genetic diversity was distributed within the population. The genetic differentiation index(Fst) of the 3 C. carpio populations was 0.1299, indicating a mildly genetic differentiation;the Ds distribution among populations ranged from 0.0248 to 0.0835, with the greatest genetic distance between the FP and SP. The results of UPGMA clustering analysis based on Ds showed that FP and LP clustered into one branch, and SP was an independent branch. Genetic structure analysis showed that 3 C. carpio populations were divided into 2 subpopulationsdisease-resistant population(SP) and susceptible populations(FP and LP). The result of C. carpio population division according to time order of mortality were basically consistent with the results of population division by cluster analysis and genetic structure analysis.【Conclusion】 The resistance of C. carpio to A. hydrophlia grows as population genetic diversity grows. Therefore, sufficient population size should be ensured during the selection and breeding of disease-resistant C. carpio strains to ensure a certain level of genetic heterozygosity while improving other economic traits such as growth and nutrition.

     

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