Abstract
Two Y chromosome specific microsatellites UMN2404 and UMN0103 were genotyped and assessed for polymorphisms in a total of 423 unrelated males from 25 indigenous Chinese cattle breeds. Consistently, both microsatellites displayed specific indicine and taurine alleles in each bull examined. The indicine and taurine alleles were detected in 248 males (58.6%), and 175 males (41.4%), respectively, although these frequencies varied amongst different breeds examined. The indicine alleles dominated in the southern group (92.4%), while the taurine alleles dominated in the northern group (95.5%). Hainan Island was possibly the site for the origin of Chinese zebu, and Tibetan cattle were probably independently domesticated from another strain of Bos primigenius. The geographical distribution of these frequencies reveals a pattern of male indicine introgression and a hybrid zone of indicine and taurine cattle in China. The declining south-to-north and east-to-west gradient of male indicine introgression in China could be explained by historical data, geographical segregation and temperature and weather conditions.
Highlights
China is rich in genetic resources of cattle breeds, with 28 indigenous and other cattle breeds [15]. These cattle breeds have been divided into three major groups on the basis of their geographical distribution, morphological characteristics and sex chromosome polymorphisms: the northern group in northern China, the central area group in the middle and lower areas of the Yellow River and the Huaihe River, and the southern group in southern China [2, 15]
The frequencies of the taurine and indicine specific alleles in the indigenous Chinese cattle breeds are shown in Figure 1 and Table I
Previous cytogenetic research on the indigenous Chinese cattle breeds showed that the male indicine Y chromosome was present in 100% of Hainan (HN), Wenling hump (WL), Ebian (EB), NY and LX males; 75% of Jiaxian Red (JX) cattle; 25% of QC bulls; and in 22.2% of JN breeds, but it was absent in Mongolia (MG) and Tibetan cattle (TB) [2, 3, 6, 19, 20]. The analysis of these data and our results indicate that the frequency of the indicine Y chromosome among Chinese cattle breeds ranged from 0 to 100%
Summary
China is rich in genetic resources of cattle breeds, with 28 indigenous and other cattle breeds [15]. The study of sex chromosome morphology and mtDNA D-loop region sequence data have indicated that the taurine (Bos taurus) had a higher genetic influence on the development of the northern group of breeds than the indicine (Bos indicus), while the indicine had a higher genetic influence on the development of the southern group of breeds. Both the taurine and indicine contributed to the formation of the central area group of cattle breeds [2, 8, 9]
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