Tongde County is located in the southeast of Qinghai Province, China, harboring rich yak genetic resources. In the present study, the complete mitochondrial genome (mitogenome) of the Tongde yak ( Bos grunniens ) was firstly sequenced using Illumina sequencing technique and the corresponding sequence characterization was identified. Our results showed that the mitogenome of Tongde yak is a circular molecule with 16,323 bp length consisting of 37 genes (13 protein-coding genes, 2 rRNA genes, 22 tRNA genes) and a non-coding control region (D-loop), which is consistent with most bovine species. The overall nucleotide composition was found as: A (33.72%), T (27.27%), C (25.80%), and G (13.21%), respectively, yielding a higher AT content (60.99%). The complete mitogenome sequence of Tongde yak would provide useful information for further studies on its genetic resource conservation and molecular breeding programmes in the future.

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Yak (Bos grunniens) is a unique livestock animal originating from the Qinghai-Tibet Plateau in China. In the current study, we investigated the maternal genetic diversity, differentiation and phylogeny of wild yak population and four domestic yak breeds (Qinghai-Gaoyuan, Huanhu, Xueduo, and Yushu) in Qinghai, China by analyzing 166 mitochondrial cytochrome b (Cytb) gene sequence variations. Our results indicated that the haplotype and nucleotide diversities of wild yak were 0.883±0.044 and 0.004±0.002, while the total haplotype and nucleotide diversities of four Qinghai domestic yak breeds were 0.646±0.040 and 0.003±0.001, respectively. Among the four Qinghai domestic yak breeds, the haplotype diversity was found to be highest in Yushu yak breed (Hd = 0.770±0.053), while the lowest was recorded in Huanhu yak breed (Hd = 0.501±0.088). Estimates of FST values showed a moderate genetic differentiation between wild yak and Huanhu yak (FST = 0.058) as well as that between Huanhu yak and Yushu yak breeds (FST = 0.052), but a weak genetic differentiation was observed between the other yak breeds/populations (-0.021＜FST＜0.037). Additionally, the clustering analysis based on RST values showed that Xueduo yak and Huanhu yak were clustered into one group, and each of the other three yak breeds/populations was separated into one group, respectively. Overall, the clustering relationship between wild yak and Yushu yak was closer. Maternal phylogenetic analysis showed that wild yak and four local yak breeds/populations in Qinghai represented in three maternal lineages (Mt-Ⅰ, Mt-Ⅱ, and Mt-Ⅲ), indicating three maternal origins in yak. Our study would provide valuable information for the conservation and utilization of wild yak and Qinghai domestic yak breeds.

Background Yak (Bos grunniens) is a unique livestock animal originating from the Qinghai-Tibet Plateau in China. In the current study, we investigated the maternal genetic diversity, differentiation and phylogeny of wild yak population and four domestic yak breeds (Qinghai-Gaoyuan, Huanhu, Xueduo, and Yushu) in Qinghai, China by analyzing 166 mitochondrial cytochrome b (Cytb) gene sequence variations. Results The haplotype and nucleotide diversities of wild yak were 0.883±0.044 and 0.004±0.002, while the total haplotype and nucleotide diversities of four Qinghai domestic yak breeds were 0.646±0.040 and 0.003±0.001, respectively. Among the four Qinghai domestic yak breeds, the haplotype diversity was found to be highest in Yushu yak breed (Hd = 0.770±0.053), while the lowest was recorded in Huanhu yak breed (Hd = 0.501±0.088). Estimates of FST values showed a moderate genetic differentiation between wild yak and Huanhu yak (FST = 0.058) as well as that between Huanhu yak and Yushu yak breeds (FST = 0.052), but a weak genetic differentiation was observed between the other yak breeds/populations (-0.021＜FST＜0.037). Additionally, the clustering analysis based on RST values showed that Xueduo yak and Huanhu yak were clustered into one group, and each of the other three yak breeds/populations was separated into one group, respectively. Overall, the clustering relationship between wild yak and Yushu yak was closer. Maternal phylogenetic analysis showed that wild yak and four local yak breeds/populations in Qinghai represented in three maternal lineages (Mt-Ⅰ, Mt-Ⅱ, and Mt-Ⅲ), indicating three maternal origins in yak. Conclusion Our study would provide valuable information for the conservation and utilization of wild yak and Qinghai domestic yak breeds.

The white yak, a unique and valuable farm animal of the Qinghai-Tibetian Plateau, is mainly distributed in Tianzhu (County of Gansu Province), Menyuan, Huzhu and Ledu (three Counties of Qinghai Province) in China. In the present study, the Y-chromosomal based genetic diversity, differentiation and phylogeny of three Chinese white yak breeds/populations (Tianzhu, Huzhu and Menyuan) were comprehensively explored using five Y-SNPs (SRY4, USP9Y, UTY19, AMELY3 and OFD1Y10) and one Y-STR (INRA189) markers. The results of this study showed that six Y-haplotypes (H1Y1, H9Y1, H10Y1, H11Y2, H12Y2 and H13Y2) were identified in 97 male yaks from three white yak breeds/populations. Among haplotypes, H1Y1, H10Y1 and H11Y2 were shared haplotypes for all of breeds/populations and H12Y2 was shared by Tianzhu and Huzhu populations. However, H9Y1 and H13Y2 haplotypes were only detected in Menyuan and Tianzhu white yak populations, respectively. The Y-haplotype diversity was maximum in Huzhu white yak (0.7500±0.0349), the medium in Tianzhu white yak (0.6881±0.0614) and lowest in Menyuan white yak (0.5720±0.0657), respectively. The total Y-haplotype diversity of three white yak breeds/populations was 0.7567±0.0233, indicating rich paternal genetic diversity in white yak. The FST values showed a moderate differentiation between Tianzhu and Menyuan (FST =0.0763, P<0.05) populations, weak differentiation between Huzhu and Tianzhu white yak breeds/populations (FST =0.0186, P>0.05) and Huzhu and Menyuan (FST =-0.005, P>0.05) populations. The clustering analysis showed a close genetic relationship between Huzhu and Menyuan white yaks and far from Tianzhu white yak breed. The phylogenetic analyses showed that white yak had two Y-haplogroups/lineages (Y1 and Y2) with two potential paternal origins. The data of present study could contribute to the conservation and utilization of special white yak genetic resources.