Aspects of genetic diversity and implications for livestock genetic conservation.

摘要

Genetic diversity benefits populations coping with ever-changing environmental conditions and provides the basis for improving economically important traits in accordance with consumer demands. However, numerous recent studies have demonstrated the continued decline in livestock genetic diversity worldwide. The objectives of this study were, therefore, to analyse the trend of genetic diversity in various livestock populations, to investigate major causes of loss of genetic diversity and to evaluate the potential benefit of optimum contribution selection (OCS) for minimizing the level of inbreeding. This study comprises analyses of pedigree data, genome-wide Single Nucleotide Polymorphisms (SNPs) data and gene-dropping simulations. Pedigree completeness and quality were determined before deriving the parameters used to measure genetic diversity. Overall, the results of this study demonstrated considerable (Ne=50) to withstand inbreeding depression. In addition, SNP marker-based analysis in BS, HO and JE populations revealed that BS vs. HO appeared to have higher population differentiation relative to the other two pairs (BS vs. JE and JE vs. HO). Thus, if each pair of the three populations was to be amalgamated, BS vs. HO would result in higher total genetic diversity, suggesting that inter-population exchange of genetic material could be carefully considered for increasing diversity while preserving sufficient genetic material of each population. Moreover, gene-dropping simulation identified a few founders with higher risk of loss of their genome in the respective reference populations. It would be prudent to make proper selection of parents of future generations in such a way that the descendants of founders with higher risk of genome loss would be selected to contribute a large number of offspring. Finally, OCS was demonstrated to be an important strategy for conserving genetic diversity. Further studies are, however, required to investigate the potential benefits of OCS to improve the genetic diversity of the populations that showed continued decline in genetic diversity over the past few decades, such as the Canadian Guernsey population.