Cao Lu, Liu Huiming, Mulder Han A, Henryon Mark, Thomasen Jørn Rind, Kargo Morten, Sørensen Anders Christian
Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, Denmark.
Wageningen University & Research, Animal Breeding and Genomics, Wageningen, Netherlands.
Front Genet. 2020 Apr 21;11:251. doi: 10.3389/fgene.2020.00251. eCollection 2020.
Genotype × environment interaction (G × E) is of increasing importance for dairy cattle breeders due to international multiple-environment selection of animals as well as the differentiation of production environments within countries. This theoretical simulation study tested the hypothesis that genomic selection (GS) breeding programs realize larger genetic benefits by cooperation in the presence of G × E than conventional pedigree-based selection (PS) breeding programs. We simulated two breeding programs each with their own cattle population and environment. Two populations had either equal or unequal population sizes. Selection of sires was done either across environments (cooperative) or within their own environment (independent). Four scenarios, (GS/PS) × (cooperative/independent), were performed. The genetic correlation ( ) between the single breeding goal trait expressed in two environments was varied between 0.5 and 0.9. We compared scenarios for genetic gain, rate of inbreeding, proportion of selected external sires, and the split-point that is the lowest value of for long-term cooperation. Between two equal-sized populations, cooperative GS breeding programs achieved a maximum increase of 19.3% in genetic gain and a maximum reduction of 24.4% in rate of inbreeding compared to independent GS breeding programs. The increase in genetic gain and the reduction in rate of inbreeding realized by GS breeding programs with cooperation were respectively at maximum 9.7% and 24.7% higher than those realized by PS breeding programs with cooperation. Secondly, cooperative GS breeding programs allowed a slightly lower split-point than cooperative PS breeding programs (0.85∼0.875 vs ≥ 0.9). Between two unequal-sized populations, cooperative GS breeding programs realized higher increase in genetic gain and showed greater probability for long-term cooperation than cooperative PS breeding programs. Secondly, cooperation using GS were more beneficial to the small population while also beneficial but much less to the large population. In summary, by cooperation in the presence of G × E, GS breeding programs realize larger improvements in terms of the genetic gain and rate of inbreeding, and have greater possibility of long-term cooperation than conventional PS breeding programs. Therefore, we recommend cooperative GS breeding programs in situations with mild to moderate G × E, depending on the sizes of two populations.
由于动物的国际多环境选择以及各国生产环境的差异，基因型×环境互作（G×E）对奶牛育种者的重要性日益增加。本理论模拟研究检验了以下假设：在存在G×E的情况下，基因组选择（GS）育种计划通过合作比传统的基于系谱的选择（PS）育种计划能实现更大的遗传效益。我们模拟了两个育种计划，每个计划都有自己的牛群和环境。两个群体的种群规模要么相等，要么不相等。种公牛的选择要么跨环境进行（合作），要么在其自身环境内进行（独立）。进行了四种情况，即（GS/PS）×（合作/独立）。在两种环境中表达的单一育种目标性状之间的遗传相关性（ ）在0.5至0.9之间变化。我们比较了不同情况下的遗传进展、近亲繁殖率、所选外部种公牛的比例以及分裂点 ，分裂点是长期合作中 的最低值。在两个规模相等的群体之间，与独立的GS育种计划相比，合作的GS育种计划实现的遗传进展最大增加了19.3%，近亲繁殖率最大降低了24.4%。合作的GS育种计划实现的遗传进展增加和近亲繁殖率降低分别比合作的PS育种计划实现的最大高出9.7%和24.7%。其次，合作的GS育种计划允许的分裂点 略低于合作的PS育种计划（0.85∼0.875对≥0.9）。在两个规模不相等的群体之间，合作的GS育种计划实现了更高的遗传进展增加，并且比合作的PS育种计划显示出更大的长期合作可能性。其次，使用GS进行合作对小群体更有益，对大群体也有益但益处要小得多。总之，在存在G×E的情况下通过合作，GS育种计划在遗传进展和近亲繁殖率方面实现了更大的改进，并且比传统的PS育种计划有更大的长期合作可能性。因此，根据两个群体的规模，我们建议在G×E为轻度至中度的情况下采用合作的GS育种计划。
