Abstract
Mitochondrial DNA has been widely used to perform phylogenetic studies in different animal species. In pigs, genetic variability at the cytochrome B gene and the D-loop region has been used as a tool to dissect the genetic relationships between different breeds and populations. In this work, we analysed four SNP at the cytochrome B gene to infer the Asian (A1 and A2 haplotypes) or European (E1 and E2 haplotypes) origins of several European standard and local pig breeds. We found a mixture of Asian and European haplotypes in the Canarian Black pig (E1, A1 and A2), German Piétrain (E1, A1 and A2), Belgian Piétrain (E1, A1), Large White (E1 and A1) and Landrace (E1 and A1) breeds. In contrast, the Iberian (Guadyerbas, Ervideira, Caldeira, Campanario, Puebla and Torbiscal strains) and the Majorcan Black pig breeds only displayed the E1 haplotype. Our results show that the introgression of Chinese pig breeds affected most of the major European standard breeds, which harbour Asian haplotypes at diverse frequencies (15–56%). In contrast, isolated local Spanish breeds, such as the Iberian and Majorcan Black pig, only display European cytochrome B haplotypes, a feature that evidences that they were not crossed with other Chinese or European commercial populations. These findings illustrate how geographical confinement spared several local Spanish breeds from the extensive introgression event that took place during the 18th and 19th centuries in Europe.
Highlights
Pig mitochondrial DNA is a 16 kb circular molecule including 13 protein-coding genes, 22 tRNA and genes responsible for 12S and 16S rRNA [7, 15]
Phylogenetic analysis of the porcine mitochondrial genome has revealed that Wild Boar subspecies were independently and simultaneously domesticated in Asia and Europe 9000 YBP [2, 6,7,8, 10]
Two distinct European clades denoted E1 and E2 have been characterised by Giuffra and coworkers [2]. The former one has been found in most of the European Wild Boars and domestic pig breeds, whereas E2 has been detected in three Wild Boars from Italy
Summary
Pig mitochondrial DNA (mtDNA) is a 16 kb circular molecule including 13 protein-coding genes, 22 tRNA and genes responsible for 12S and 16S rRNA [7, 15]. Major European and Asian mtDNA clades diverged well before this domestication event and the estimates for the time of divergence range from 58 000 to 900 000 YBP [1, 2, 6, 7, 10]. Two distinct European clades denoted E1 and E2 have been characterised by Giuffra and coworkers [2]. The former one has been found in most of the European Wild Boars and domestic pig breeds, whereas E2 has been detected in three Wild Boars from Italy. Our main goal was to compare the prevalence of Asian haplotypes in three of the major commercial European pig breeds with regards to three local European pig populations which have remained geographically isolated for a long time span
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