Genetic Relationships Among Five Zebu Breeds Naturalized in America Accessed with Molecular Markers

This study aims to analyze the within-breed genetic diversity and determine the genetic relationships among the most important zebu populations introduced in the American continent from Asia. Gyr (GYR), Red Sindhi (SIN), Nellore (NEL), Guzerat (GUZ) and the synthetic Brahman (BRH) breeds have been established especially in American tropical regions. Estimates of genetic structure and diversity were carried out within and among the five populations studied. The results of withinbreed genetic diversity showed medium to high medium values of diversity in all genetic parameters [observed heterozygosity (H o )=0.622±0.022; expected heterozygosity (H e )=0.662±0.023; number of alleles (N a )=5.71±1.63; and allelic richness (A r )=4.097±0.958]. The lowest value of H o was observed in NEL (0.569±0.019) and the highest in BRH (0.688±0.015). Lowest value of H e was also observed in NEL (0.612±0.024) and the highest in BRH (0.700±0.020). Gyr, GUZ and NEL showed high estimations of inbreeding, 9.98, 7.92 and 6.83% respectively. Values of N a varied between 4.93±1.52 in GUZ and 7.04±1.99 in BRH and the A r values ranged between 3.687±0.895 in NEL and 4.42±1.91 in SIN. On the other hand, although phenotypically, the five breeds are clearly distinguishable, the genetic analysis of structure and kinship demonstrates a total independence among GYR, GUZ and NEL, while BRH and Red Sindhi show a closed relationship. These facts support that GYR, GUZ and NEL have had a diverse origin but also different models of introgression in America. Brahman and SIN could be explained by the intervention of the Sindhi ancestors in the formation of the American synthetic Brahma.