婆罗门牛mtDNA D-loop变异及其遗传背景
Mitochondrial DNA D-loop Variation and Genetic Background of Brahman Cattle
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摘要: 对10头原种婆罗门牛mtDNA D-loop全序列912 bp测序，婆罗门牛遗传多样性丰富，检测到的9种单倍型兼有瘤牛(B. indicus)与普通牛(B. taurus)的遗传背景，核苷酸变异率为6.25%，单倍型多态度为0.978±0.054，核苷酸多态度为0.014 30±0.008 68。所有单倍型聚为明显的两大分支，婆罗门牛的大部分单倍型为普通牛单倍型类群， 并占绝对优势(90%)，仅Brah-6与亚洲瘤牛聚在一起，属于亚洲瘤牛线粒体单倍型，表明婆罗门牛的确是集亚洲瘤牛、欧洲普通牛等优良特性于一身(易产犊、产肉性能好、耐热与体表寄生虫等)的瘤牛品种之一。育种学家引种瘤牛的目的是改善当地牛的生产力与适应性，现代普通牛表现出明显又普遍的瘤牛渐渗现象。对现代的瘤牛品种而言，除亚洲瘤牛品种外，普通牛对其他瘤牛品种育成的贡献同样高。 支持瘤牛(B. indicus)为独立驯化、起源于印度次大陆的假说。Abstract: The complete mitochondrial DNA D-loop sequences from 10 stud Brahman cattle were sequenced and analyzed. The results showed that the genetic diversity of Brahman cattle was rich; the rate of nucleotide variation, haplotype diversity and nucleotide diversity were 6.25%, 0.978±0.054 and 0.014 30±0.008 68, respectively. Nine haplotypes were defined and fell into two distinct lineages, suggesting that Brahman cattle have both Bos indicus (Zebu) and B. taurus genetic background. The taurine haplotypes were predominant at 90% and only Brah-6 belonged to the Asian zebu mthaplotype. This indicates that Brahman cattle was one of the zebu breeds and inherited the excellent characteristics of both the Asian zebu and European beef cattle, such as easy calf delivery, high quality beef, heat tolerance and resistance to various parasites. Breeders introduced Brahman cattle to improve the productivity and adaptability of native cattle. The Zebu has evidently frequently introgressed into the modern taurine breeds. As for modern zebu breeds, B. taurus also highly contributed to their formation, except for the Asian zebu. Furthermore our results also confirm the hypothesis that B. indicus has undergone a separate domestication event and originated from the Indian subcontinent.
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