Genome-wide insights into population structure and genetic history of tunisian local cattle using the illumina bovinesnp50 beadchip

Tunisian local cattle populations are at risk of extinction as they were massively crossed with imported breeds. Preservation of indigenous livestock populations is important because each of them comprises a unique set of genes resulting from a local environment-driven selection that occurred over hundreds of years. The diversity and genetic structure of Tunisian local cattle populations are poorly understood. However, such information is crucial to the conservation and sustainable use of genetic resources. In addition, comparing the genomic structure of population sets from different parts of the world could help yield insight into their origin and history. In the present study, we provide a detailed assessment of the population structure of the three Tunisian local cattle populations using various methods, and we highlight their origin and history by investigating approximately ~38,000 SNPs in a broad panel of 878 individuals from 37 worldwide cattle breeds representative of African, European and indicine populations.[br/]Our study revealed a low level of divergence and high genetic diversity in Tunisian local cattle reflecting low levels of genetic drift. A Comparison with the worldwide cattle panel pinpointed the admixed origin of the genome of the three Tunisian populations with the two main European and African ancestries. Our results were in agreement with previous historical and archaeological reports about the past gene flow that existed between North African and South European breeds, in particular with Iberian cattle. We also detected a low-level indicine introgression in the three Tunisian populations and we inferred that indicine ancestry was inherited via African ancestors.[br/]Our results represent the first study providing genetic evidence about the origin and history of Tunisian local cattle. The information provided by the fine-scale genetic characterization of our study will enhance the establishment of a national conservation strategy for these populations. These results may enable the identification of genetic variants involved in adaptation to harsh environmental conditions.