The genetic diversity of Zaosheng native cattle (Bos taurus) and associated crossbred population.

Maternally inherited mitochondrial DNA(mtDNA) has been used extensively to determine genetic diversity, guide genetic resource conservation, and determine phylogeny. Zaosheng cattle, mainly produced in Qingyang Prefecture of Gansu, were introduced to Pingliang, Guyuan, and other areas coinciding with the growth of farming culture. Local genetic groups in various locations were formed through long term domestication and adaptation, respectively. To investigate the genetic diversity of Zaosheng cattle, six Zaosheng cattle groups(Qingyang group, QZ; QZ × South Devon group, QZ × N; Pingliang group, PZ; PZ ×Simmental, PZ×X; Guyuan group, GZ; GZ×Qinchuan cattle, GZ×Q) were analyzed using mtDNA D-loop. A total of 131 variable sites and 103 haplotypes were identified. Among the QZ, PZ and GZ groups, the average number of nucleotide differences(13.884, 10.266, 3.111, respectively) and nucleotide diversity(0.022 95,0.016 82, 0.005 11, respectively) decreased. Similar results were observed in QZ×N, PZ×X and GZ×Q groups(15.362, 9.264, 7.495, respectively; and 0.025 31, 0.015 24, 0.012 33, respectively for nucleotide differences and diversity). There were 6 shared and 32 unique haplotypes found in the QZ group, which was greater than PZ(6 shared, 9 unique)and GZ(2 shared, 5 unique). In conclusion, the genetic diversity of QZ and QZ×N was higher than other groups, and the genetic diversity of crossbred groups was similar to native groups.Consequently, crossbreeding had little influence on mtDNA genetic diversity in Zaosheng cattle and crossbreeding of Zaosheng cattle was generally through paternal crosses. We can also draw a conclusion that Zaosheng cattle in Pingliang and Guyuan could have migrated from Qingyang and gradually formed two maternal branches and provide a scientific foundation for genetic resources conservation of Zaosheng native cattle.