Genetic relationships and population structure in three Italian Merino-derived sheep breeds

The Merino-derived breeds represent a significant animal resource in terms of genetic diversity and socio-economic relevance. The aim of this investigation was to define the population structure and the genetic diversity of the Sopravissana, Merinizzata Italiana and Gentile di Puglia breeds by employing 30 microsatellite molecular markers, also taking Spanish Merino and Appenninica breeds into account, which are thought to represent the male and the female ancestors, respectively, of the Italian Merino-derived breeds. A further objective of this study was to remark on an issue generally linked to the development of genetic groups that are spread worldwide: the degree to which geographic effects and genetic origins are significantly influential in the evolution of a cosmopolitan genetic group, such Merino sheep. Blood samples from 174 individuals were collected and genotyped. A total of 366 alleles were detected. The mean number of alleles per breed ranged from 7.22 for Gentile di Puglia to 8.21 for Merinizzata Italiana. The mean values of observed heterozygosity (0.71) and expected heterozygosity (0.75) were high, suggesting that the total analysed population is characterised by noticeable genetic variability. The Fis calculated in each breed showed that a slight degree of heterozygosity deficiency exists within each breed. The Fst value calculated (0.048) (P<0.05) indicated the existence of poor segmentation among the subpopulations. According to the Fst genetic distance estimates, the most closely related breeds were Merinizzata Italiana and Gentile di Puglia (0.013). The genetic tree built using the Reynolds weighted genetic distance among populations shows the Merino-derived breeds occurring within a well-defined area, together with the Spanish Merino breed, confirming their hypothetical origin. STRUCTURE analysis showed that Sopravissana and, especially, Gentile di Puglia were breeds that were split into several genetic patterns, suggesting a significant occurrence of admixture within these breeds. The results arising from our microsatellites analysis could represent a starting point for planning aimed at the safeguarding and valorisation of the three Italian Merino-derived sheep breeds. © 2010 Elsevier B.V