Assessment of Heterozygosity in European Local and Cosmopolitan Pig Populations

Researchers focused on assessing differences in gene diversity within and between populations, whether cosmopolitan or local. However, the identification of patterns of variation in non-random heterozygous genomic stretches, known as Heterozygosity-Rich regions (HRRs), has not yet been determined in European local pig breeds. A total of 23 pig breeds (20 local and 3 cosmopolitan) were assessed and compared in terms of heterozygosity-rich regions. The breeds with the highest number of HRRs were Large White, Lithuanian Old type, and Landrace, followed by Lithuanian Native, Mora Romagnola, and Duroc. The breeds with the lowest number were Alentejana, Iberian, and Majorcan Black. No shared HRR islands were found in all breeds, but gene enrichment analysis performed in the most common HRRs revealed several biologically important genes that cluster together and play significant roles, primarily related to the immune system. Permutation analysis indicated that some local breeds serve as true reservoirs of genetic diversity, displaying distinct and unique characteristics in terms of heterozygosity. This study suggests the importance of investigating heterozygosity to develop a comprehensive picture of pig breeds, regardless of the production system, country of origin, or population size.