Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering College (NIBGE-C), Faisalabad, Pakistan.
Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad, Pakistan.
Mamm Genome. 2023 Dec;34(4):602-614. doi: 10.1007/s00335-023-10019-y. Epub 2023 Oct 7.
Linkage disequilibrium (LD) affects genomic studies accuracy. High-density genotyping platforms identify SNPs across animal genomes, increasing LD evaluation resolution for accurate analysis. This study aimed to evaluate the decay and magnitude of LD in a cohort of 81 crossbred dairy cattle using the GGP_HDv3_C Bead Chip. After quality control, 116,710 Single Nucleotide Polymorphisms (SNPs) across 2520.241 Mb of autosomes were retained. LD extent was assessed between autosomal SNPs within a 10 Mb range using the r statistics. LD value declined as inter-marker distance increased. The average r value was 0.24 for SNP pairs < 10 kb apart, decreasing to 0.13 for 50-100 kb distances. Minor allele frequency (MAF) and sample size significantly impact LD. Lower MAF thresholds result in smaller r values, while higher thresholds show increased r values. Additionally, smaller sample sizes exhibit higher average r values, especially for larger physical distance intervals (> 50 kb) between SNP pairs. Effective population size and inbreeding coefficient were 150 and 0.028 for the present generation, indicating a decrease in genetic diversity over time. These findings imply that the utilization of high-density SNP panels and customized/breed-specific SNP panels represent a highly favorable approach for conducting genome-wide association studies (GWAS) and implementing genomic selection (GS) in the Bos indicus cattle breeds, whose genomes are still largely unexplored. Furthermore, it is imperative to devise a meticulous breeding strategy tailored to each herd, aiming to enhance desired traits while simultaneously preserving genetic diversity.
连锁不平衡(LD)会影响基因组研究的准确性。高密度基因分型平台可识别动物基因组中的 SNP,提高 LD 评估分辨率,从而实现准确分析。本研究旨在使用 GGP_HDv3_C Bead Chip 评估 81 头杂交奶牛群体中的 LD 衰减和幅度。经过质量控制后,保留了位于 2520.241 Mb 常染色体上的 116,710 个单核苷酸多态性(SNP)。使用 r 统计量评估了 10 Mb 范围内常染色体 SNP 之间的 LD 程度。随着标记间距离的增加,LD 值下降。SNP 对之间的距离小于 10 kb 时,平均 r 值为 0.24,距离为 50-100 kb 时降低至 0.13。次要等位基因频率(MAF)和样本量对 LD 有显著影响。较低的 MAF 阈值导致较小的 r 值,而较高的阈值则显示出较大的 r 值。此外,较小的样本量表现出较高的平均 r 值,特别是对于 SNP 对之间较大的物理距离间隔(>50 kb)。当前世代的有效群体大小和近交系数分别为 150 和 0.028,表明遗传多样性随时间减少。这些发现表明,利用高密度 SNP 面板和定制/特定品种 SNP 面板是开展全基因组关联研究(GWAS)和实施基因组选择(GS)的理想方法,因为这些方法在印度牛品种的基因组中仍有很大的探索空间。此外,制定针对每个牛群的精细育种策略至关重要,旨在提高理想性状的同时保持遗传多样性。