| With the rapid development of the society, the requirement for animal products is higher and higher, which forces us to cultivate new breeds and atrains. So we have to know about the genetic resources by the use of molecular genetic marker in order to utilize them thoroughly. MtDNA is the only extranuclear germ plasm of vertebrate and is a very useful marker for studies of genetic variability among populations because of absence of recombination, high substitution rate and maternal heredity. In the study, 700bp of hypervariable region of mtDNA D-loop was sequenced in 104 individuals from 20 breeds (strains) raised in China. 20 sites were polymorphic with 18 transitions, one transversion and one insertion/deletion. Among the transitions, C/T amounted to 66.7% and AIG was 33.3%, such patterns of variability were comparable with those described for other animals. According to the base substitutions, 8 haplotypes were identified. Al was the most common haplotype and encountered 89 times. Except that four animals of Yufeng brown rabbit and Zhenhai thick-hair Angora rabbit exhibited with other haplotypes, all individuals from Chinese breeds (strains) possessed such haplotype. This haplotype was also observed in all imported strains except Zika Great Rabbit. Haplotype 01 was possessed by all individuals of Zika Great Rabbit and two animals from New Zealand White Rabbit and Rex rabbit from Germany, respectively. The frequency of such haplotype was 6.73%. Moreover, it was found that haplotype diversity and nucleotide diversity of those imported breeds (strains) were higher than those of Chinese breeds (strains), though both of them were very low with 0.358, 0.00432 and 0.15 1, 0.00117, respectively. Combining such 104 sequences with the published sequences of Oryctolagus cuniculus, there were 37 haplotypes. An NJ tree rooted by Lepus capensis was constructed by the program Mega. All sequences were divided into two branches, lineage I and lineage II, the latter was composed of two clusters, I and II. All 4 sequences discovered in this study belonged to lineage 11. I-Iaplotypes Al, RI, Y6, Z2, Z7 and 01 were scattered in cluster I , while the other two haplotypes 01 and Y7 belonged to cluster 11. Medial network analysis indicated the same results, a highly represented haplotype (Al and 01 respectively) was centered through which other sequences rooted to the rest of the phylogeny. Notably, most sequences fell within only several substitutions of the central sequence. An NJ tree was constructed to illustrate the relationships between breeds (strains) according to the sequences of D-loop. There was only one shared haplotype, Al, in all individuals of 12 breeds (strains) such as Qixing Meat rabbit, Californian rabbit, the genetic distance between such breeds was zero and they clustered closely. While the distances between Zika Great Rabbit and other breeds were far. In conclusion, based on mtDNA D-loop analysis, there was a senous scarcity of genetic diversity of Chinese rabbits and the differentiation among the breeds (strains) was not significant. Moreover, Chinese native rabbits might originate from one maternal of European animals, cluster I , and the other maternal, cluster II, began to contribute to the cultivated strains. In this study, we also did some analysis about nuclear gene. Because MI-IC was highly related with the disease-resistance of animal and the diversity was focused o... |
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