【作者】 谢文美；

【导师】 雷初朝；

【作者基本信息】 西北农林科技大学 ， 遗传学， 2008， 硕士

【摘要】 我国水牛有着7000多年的驯化和选择历史,在分类学上属于沼泽型水牛,具有丰富的遗传资源。由于对我国地方水牛类群的遗传多样性及遗传特性缺乏全面和系统的认识,其利用方式往往只限于作为母本,用外来品种作为父本进行杂交改良,导致我国某些地方水牛类群的遗传多样性逐渐下降、甚至出现某些类群的遗传资源已近灭绝。但对我国水牛的起源进化及遗传多样性研究还不够全面和深入,为了更好的保护和利用我国珍贵的地方水牛类群的遗传资源,本研究对我国22个水牛类群共455个个体mtDNA D-loop区全序列进行统计分析,研究中国水牛的母系起源、类群之间的系统进化关系及遗传多样性,得到如下结果:1.中国22个水牛类群455个个体mtDNA D-loop区全序列长度为894 bp～920 bp,最常见的为916bp,长度多态性是由于全序列中存在三个较为特异的polyG/C造成的。2.检测到148种单倍型114个核苷酸多态位点,约占所测核苷酸总长的12.36%, 97个转换,12个颠换,5个转换与颠换共存,显示出碱基替换有明显的偏倚。其单倍型多样度(H)为0.4000±0.2373～1.0000±0.1265;核苷酸多样度(π值)为0.0070±0.0 039～0.0219±0.0116,表明中国水牛具有丰富的遗传多样性。3.mtDNA D-loop序列的NJ系统发育树和网络分析表明,中国沼泽型水牛具有两大支系,即支系A和支系B,支持中国水牛有2个母系起源的观点。支系B又可分为两个亚支,本研究首次命名为亚支B1和亚支B2。4.我国22个地方水牛类群间没有明显的群体结构。中国水牛各类群间都包含有两个主要的母系起源支系,类群间遗传分化不明显,但是支系内、群体间差异显著,但分化较小,同时支系B的分化程度较A支系较大,为较为古老的一支。5.对中国水牛两个支系的所有个体分别进行不配对分析,发现支系A表现线性降低的不配对分布,支系B分布曲线表现光滑的正态分布曲线,且亚支系B2及亚支系B1分布曲线均呈单峰型, Fs值分别为-26.32,-24.73,-21.09和-13.27,P值均小于0.01,显著偏离中性,表明各支系均曾经历了群体扩张,且主要支系A经历了最大的群体扩张,支系B经历了较小的两次群体扩张。更多还原

【Abstract】 China is one of the countries that have the richest swamp buffalo resources in the world ,it has been domesticate and selected for 7000 years, which belonged swamp buffalo. Because of lacking comprehensive and systematic knowledge on the genetic diversity and characteristics of indigenous buffalo types, we only used the native breeds as the female parents and the foreign breeds as the male parents to hybrid, which has led to the decline of the genetic diversity of buffalo gradually and even the distinct of some genetic resource of buffalo soon. For we do not had a complete and deep knowing the domestic and genetic diversity of the China buffalo, to protect and use the domestic buffalo genetic resource perfectly, Through analyzing the mtDNA D-loop of 455 samples from 22 Chinese indigenous buffalo types, we studied the maternal origin of the buffalos, the phylogenetic relations between genetic varieties and diversity and got these results as follows:1. The length of the complete mtDNA D-loop sequences varied from 894bp to 920 bp in 455 individuals of 22 Chinese buffalo types. Most is 916 bp, this is because there are three special polyG/C in the complete sequence.2. 114 sites are polymorphic in 148 hyplotypes with 12.36% of 915 bp D-loop region, 97 of these sites are transitions,12 of them are transvertions, 5 of these sites have both transitions and transvertions. it is suggesting that the base bias which is in proportion to mammalian mitochondrial DNA nucleotide composition. The haplotype diversity and nucleotide diversity were 0.4000±0.2373～1.0000±0.1265 and 0.0070±0.0 039～0.0219±0.0116, respectively, indicating abundant genetic diversity in Chinese buffalo populations.3. NJ phylogenetic and a reduced median network analysis in Chinese buffalo mtDNA revealed two highly divergent, namely lineages A and B. which suggested that Chinese native buffalo may have two maternal origins. The lineage B also divided two bio-lineage, we first called them B1 and B2.4. There is poor population structure among 22 Chinese buffalo types. All the China buffalo types had two lineages, poor genetic difference. But in the lineages, types/population had the obvious difference, little variation; also the lineage B as the older lineage is deeper than the lineage A.5. There happened two population expansion events in Chinese swamp buffalo. Mismatch distributions of lineages A、B1 and B2. showed one peak, also Fs values were -26.32(P<0.01), -21.09 (P<0.01) and -13.27(P<0.01), respectively, which suggested Chinese buffalo lineage A underwent population expansion events, and lineage A did a larger one. And lineage B shows two peak -24.73(P<0.01)which suggestes lineage B has underwent two smaller population expansion events.更多还原