The East Balkan Swine (EBS) is the only indigenous pig breed in Bulgaria. We analyzed the mitochondrial DNA (mtDNA) control region and 21 microsatellite loci for 198 individuals from 11 farms in Bulgaria. Obtained 11 mtDNA haplotypes including three novel ones were grouped to two major clades, European clade E1 (146/198 individuals, 73.7%) and Asian clade A (52/198, 26.3%). The mixture of the two clades may have resulted from historical crossbreeding between the European and Asian pig breeds. Clade A was frequent in southeastern Bulgaria (Burgas Province), but less frequent or absent in northeastern Bulgaria (Varna and Shumen Provinces). The distribution of Europe- and Asia-specific haplotypes relative to EBS farm locations could be attributed to regional differences of breeding systems (e.g., crossbreeding with imported commercial pigs). A microsatellite analysis showed high heterozygosities for all the EBS farms, and negative inbreeding coefficients presumably due to crossing with commercial pigs or wild boars and/or efforts to reduce inbreeding by farmers. Bayesian clustering analyses showed that all farm populations are genetically well distinguishable from one another. Although diversity has been maintained by the efforts of farmers and a breeding association, the effective population size remains small, and conservation efforts should be continued.

中文翻译：

---

线粒体 DNA 和微卫星分析揭示了保加利亚东巴尔干猪 (Sus scrofa) 的种群遗传结构和多样性

东巴尔干猪 (EBS) 是保加利亚唯一的本土猪品种。我们分析了来自保加利亚 11 个农场的 198 个个体的线粒体 DNA (mtDNA) 控制区和 21 个微卫星位点。获得 11 个 mtDNA 单倍型，包括三个新的单倍型，分为两个主要进化枝，欧洲进化枝 E1（146/198 个个体，73.7%）和亚洲进化枝 A（52/198，26.3%）。这两个进化枝的混合可能是欧洲和亚洲猪品种之间历史杂交的结果。进化枝 A 在保加利亚东南部（布尔加斯省）很常见，但在保加利亚东北部（瓦尔纳省和舒门省）不太常见或不存在。欧洲和亚洲特定单倍型相对于 EBS 农场位置的分布可归因于育种系统的区域差异（例如，与进口商品猪的杂交）。微卫星分析显示所有 EBS 农场的杂合度都很高，并且近亲繁殖系数为负，这可能是由于与商品猪或野猪杂交和/或农民减少近亲繁殖的努力。贝叶斯聚类分析表明，所有农场种群在遗传上都可以很好地区分。尽管农民和育种协会的努力维持了多样性，但有效种群规模仍然很小，保护工作应继续进行。