1. Genetic Diversity of Central Thailand Beef Cattle Revealed by Mitochondrial DNA Data Kanya Jirajaroenrat 1* , Saranya Satitmanwiwat 2 , Kunya Tuntivisoottikul 3 1 Department of Animal Production Technology, Faculty of Agricultural Technology, 2 Agricultural Biotechnology Program, Faculty of Agricultural Technology, 3 Department of Agricultural Education, Faculty of Industrial Education, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand * Corresponding auther: kjkanya@kmitl.ac.th Summary Thai native beef cattle are an important breed which is able to adapt to harsh environment and local feedstuff. To date, little genetic data on Thai native cattle has been gathered. This research was performed to study the polymorphism of the D-loop sequence in mitochondrial DNA of the native cattle in the central region of Thailand. Twenty five beef samples were collected from Prachuapkhirikhan, Kanchanaburi, Nakornpathom and Ratchaburi provinces. DNA was extracted and then the D-loop mitochondrial DNA fragments were amplified by PCR technique. The D-loop sequences confirmed that the Central Thailand beef cattle in this study belonged to Bos indicus specie, while seven haplotypes were identified. In the rooted neighbor-joining tree, the Central Thailand cattle were divided into two main groups. Haplotype ct1 harbored 15 members, mostly samplings from Prachuapkhirikhan and closely related to the B. indicus cattle from India, Nepal, Philippines and China. The rest of the haplotypes (ct2-ct7) fell into another cluster located apart from the main groups. This result indicated that some cattle in Central Thailand could constitute a new cluster of the B. indicus cattle type. Keywords: mtDNA, D-loop, Genetic diversity, Central Thailand, Beef cattle Introduction Thai beef cattle are one of the most economically important domestic animals in Thailand. The origin, genetic diversity, conservation, and sustainable utilization of this species have become a topic of close attention. The variation of mitochondrial DNA (mtDNA) at a displacement loop region (D-loop) has been widely used to elucidate the origin and diversity of animals. By this approach, the European and African cattle breeds have been grouped into a distinct clade from the Indian cattle (Loftus et al., 1994). Further study reported that cattle samples from Africa belonged to a cluster separated from that of Near East and Western Europe (Troy et al., 2001). An initial examination of East Asia cattle mtDNA classified Bos taurus from Japan, Mongolia, and Korea into four geographically distributed clusters whereas the B. indicus mtDNA sequences were found only in cattle from Mongolia (Mannen et al., 2004). Additionally, a study of Chinese cattle grouped B. taurus samples into three clusters, and B. indicus samples into two clusters (Lai et al, 2006).