The pig breeding industry has undergone a large number of mergers in the past decades. Various commercial lines were merged or discontinued, which is expected to reduce the genetic diversity of the pig species. The objective of the current study was to investigate the genetic diversity of different former Dutch Landrace breeding lines and quantify their relationship with the current Dutch Landrace breed that originated from these lines. Principal component analysis clearly divided the former Landrace lines into two main clusters, which are represented by Norwegian/Finnish Landrace lines and Dutch Landrace lines. Structure analysis revealed that each of the lines that are present in the Dutch Gene bank has a unique genetic identity. The current Dutch Landrace breed shows a high level of admixture and is closely related to the six former lines. The Dumeco N-line, which is conserved in the Dutch Gene bank, is poorly represented in the current Dutch Landrace. All seven lines (the six former and the current line) contribute almost equally to the genetic diversity of the Dutch Landrace breed. As expected, the current Dutch Landrace breed comprises only a small proportion of unique genetic diversity that was not present in the other lines. The genetic diversity level, as measured by Eding’s core set method, was equal to 0.89 for the current Dutch Landrace breed, whereas total genetic diversity across the seven lines, measured by the same method, was equal to 0.99. The current Dutch Landrace breed shows a high level of admixture and is closely related to the six former Dutch Landrace lines. Merging of commercial Landrace lines has reduced the genetic diversity of the Landrace population in the Netherlands, although a large proportion of the original variation is maintained. Thus, our recommendation is to conserve breeding lines in a gene bank before they are merged.

中文翻译：

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商业育种系合并对长白猪遗传多样性的影响

过去几十年来，生猪养殖业经历了大量的兼并。各种商业品系被合并或终止，预计这将减少猪种的遗传多样性。本研究的目的是调查不同的前荷兰长白品种育种品系的遗传多样性，并量化它们与源自这些品系的当前荷兰长白品种的关系。主成分分析清楚地将以前的长白品系分为两个主要簇，以挪威/芬兰长白品系和荷兰长白品系为代表。结构分析显示，荷兰基因库中的每个品系都具有独特的遗传特性。目前的荷兰长白品种表现出高水平的混合性，并且与之前的六个品系密切相关。荷兰基因库中保存的 Dumeco N 系在目前的荷兰长白品种中很少有体现。所有七个品系（前六个品系和当前品系）对荷兰长白品种的遗传多样性的贡献几乎相同。正如预期的那样，目前的荷兰长白品种仅包含一小部分其他品系中不存在的独特遗传多样性。目前荷兰长白品种的遗传多样性水平（通过 Eding 核心集方法测量）等于 0.89，而通过相同方法测量的七个品系的总遗传多样性等于 0.99。目前的荷兰长白品种表现出高水平的混合性，并且与前六个荷兰长白品系密切相关。尽管大部分原始变异得以保留，但商业长白品种的合并降低了荷兰长白品种种群的遗传多样性。因此，我们的建议是在合并之前将育种系保存在基因库中。