The genetic relationships of five Indian horse breeds, namely Marwari, Spiti, Bhutia, Manipuri and Zanskari were studied using microsatellite markers. The DNA samples of 189 horses of these breeds were amplified by polymerase chain reaction using 25 microsatellite loci. The total number of alleles varied from five to 10 with a mean heterozygosity of 0.58^0.05. Spiti and Zansakari were the most closely related breeds, whereas, Marwari and Manipuri were most distant apart with Nei's D A genetic distance of 0.071 and 0.186, respectively. In a Nei's D A genetic distances based neighbour joining dendrogram of these breeds and a Thoroughbred horse outgroup, the four pony breeds of Spiti, Bhutia, Manipuri and Zanskari clustered together and then with the Marwari breed. All the Indian breeds clustered independently from Thoroughbreds. The genetic relationships of Indian horse breeds to each other correspond to their geographical/environmental distribution.Keywords: genetic diversity, horse breeds, India, microsatellite markers
IntroductionThe Indian horse breeds are distinct not only because of their adaptation to different agro-climatic conditions prevailing in the country, but also because they have unique traits such as sturdiness, stiffness, endurance potential, relative disease resistance etc. However, the changed scenario after development of the road network and mechanisation combined with indiscriminate breeding with exotic or nondescript animals has led to drastic decline in the populations of these breeds. Since, presently only a few thousand true breeding horses of each of these breeds are available (Singhvi, 2001;Yadav et al., 2001), it is necessary to evolve strategies for their conservation. The evaluation of genetic diversity/relationships among livestock breeds is an important prerequisite for developing cost-effective and meaningful breed conservation/improvement programmes. The microsatellite DNA markers, due to their highly polymorphic nature, have been extensively employed in the analysis of genetic diversity amongst breeds of various livestock species including horses (Bjornstad et al., 2000;Cañ ó n et al., 2000;Kelly et al., 2002;Tozaki et al., 2003;Achmann et al., 2004;Aberle et al., 2004;Solis et al., 2005;Glowatzki-Mullis et al., 2006). The present study was undertaken to characterise five Indian horse breeds for genetic variation and to establish relationships amongst them using a set of 25 microsatellite markers. The Thoroughbred horses, which are most common exotic horses in India, were also included in our study as an outgroup.
Material and methods
SamplesThe blood samples were collected from 189 horses of five Indian horse breeds from their respective areas of distribution (Figure 1). The breeds involved and their sample sizes were: Marwari (42), Spiti (32), Bhutia (26), Manipuri (47) and Zanskari (42). The blood samples were also collected from Thoroughbred (24) horses from Haryana state. The Marwari horses are native to Marwar region of Rajsthan province and are supposed to have been evol...