1 INTRODUCTION
Yak (Bos grunniens ), known as the ”boat of the plateau”, is a
vulnerable bovine species endemic to the Qinghai-Tibet Plateau (QTP)
with an altitude of 2,000~6,000m above sea level (Qiu et
al., 2012; Wang et al., 2011). At present, there are more than 15
million wild and domestic individuals worldwide, but about 95% of which
are lived in China (Wiener et al., 2003). Qinghai Province of China owns
abundant yak genetic resources. It possessed four officially recognized
indigenous breeds (Qinghai-Gaoyuan, Huanhu, Xueduo, Yushu) and two
improved breeds (Datong and Ashdan). Mitochondrial DNA (mtDNA) owns the
characteristics of maternal inheritance and high variation rate, that
making it as an important molecular marker to explore the evolution
history, origin and genetic diversity of mammals (Bruford et al., 2003;
Lunkina et al., 2004; Srivastava et al., 2015; Maltsev et al., 2015).
The mammalian cytochrome b gene
(Cytb ), located in the
functional region of mitogenome, is a mitochondrial oxidative
phosphorylation complex protein encoding 379 amino acids (Hatefi,
2018). Compared with the mtDNA D-Loop region, Cytb is more
conserved and also has been widely used in the studies on animal’s
population genetics in recent years. Previously, some studies analyzed
mtDNA D-loop region to explore the maternal genetic diversity of wild
yak and Qinghai domestic yak populations (Ma et al., 2010; Wang et al.,
2010), but relatively few studies are done based on Cytbvariations. Again, to date, most Cytb studies conducted have
focused explicitly on a few Chinese yak populations (e.g. Bazhou, Jiali,
Sangsang, Sangri, Gongbujiangda, Sibu, Pali, Kangbu, Jiangda, Leiwuqi,
Dingqing, Baqing, Zhongdian, Taxkorgan, Karakorum-Pamir, Shenzha, and
wild yak) (Yang et al., 2009; Chang et al., 2010; Ji et al., 2012; Wang
et al., 2013; Tu et al., 2016; Hu et al., 2018; Liu et al., 2019; Li et
al., 2019; Ji et al., 2019; Wang et al., 2021), but which were limited
to four domestic yak breeds in Qinghai Province of China (Wang et al.,
2021).
In this study, we comprehensively analyzed maternal genetic diversity
and differentiation of six wild and domestic yak breeds/populations
(wild, Qinghai-Gaoyuan, Huanhu, Xueduo, and Yushu yak) in Qinghai, and
explored their clustering relationship and phylogeny based onCytb sequence variations so as to provide baseline information
for the conservation and utilization of these valuable yak genetic
resource.