Italian local chicken breeds: a comparative analysis of biodiversity on a global scale

Background: Chickens, domesticated around 3500 years ago, are crucial in global agriculture, resulting in hundreds of breeds worldwide. In Europe, intensive breeding has led to the creation of numerous distinct commercial lines at the expense of local breeds. As a result, local breeds, which are not subject to rigorous selective practices, face higher risks of genetic problems due to a narrower genetic base. Modern genotyping and bioinformatic approaches allow detailed genetic analysis. This study offers a comprehensive genetic overview of Italian chicken biodiversity compared to global breeds, emphasizing the importance of preserving local genetic diversity. Results: Hundred and ninety-two chicken breeds from various countries were analyzed, with Italian breeds being highly represented. Genetic relationships showed that Italian breeds clustered with some European, African, and Asian breeds. The ADMIXTURE analysis identified 25 distinct populations and highlighted genetic similarities of certain Italian breeds with German, French, and Swiss ones. Genetic diversity was high in African and some Asian and European breeds, with Italian breeds exhibiting moderate diversity and variability. The TreeMix analysis revealed significant migration events and evolutionary clustering. The Italian breeds had close genetic ties and some highlighted evidence of genetic introgression from common ancestors. Conclusions: Italian chicken breeds have significant genetic relationships with European, Asian, and African breeds, reflecting historical trade and breeding exchanges. Southern Italian breeds form a distinct genetic group, highlighting regional uniqueness. Overall, the research points out the need for conservation strategies to preserve genetic diversity and account for historical and contemporary gene flows, ensuring the sustainability of Italian chicken biodiversity in the face of environmental and agricultural challenges.