Toro Ospina Alejandra M, Maiorano Amanda Marchi, Curi Rogério A, Pereira Guilherme L, Zerlotti-Mercadante Maria Eugenia, Dos Santos Gonçalves Cyrillo Joslaine Noely, Aspilcueta-Borquis Rusbel R, de V Silva Josineudson A Ii
Faculty of Agricultural and Veterinary Sciences, Genetic Animal Breeding, Sao Paulo State University, Jaboticabal, Brazil.
Department of Breeding and Animal Nutrition, Faculty of Veterinary Medicine and Animal Science, Sao Paulo State University, Botucatu, Brazil.
Reprod Domest Anim. 2019 Dec;54(12):1524-1531. doi: 10.1111/rda.13559. Epub 2019 Oct 13.
Linkage disequilibrium (LD) plays an important role in genomic selection and mapping of quantitative trait loci (QTL). This study investigated the pattern of LD and effective population size (N ) in Gir cattle selected for yearling weight. For this purpose, 173 animals with imputed genotypes (from 18 animals genotyped with the Illumina BovineHD BeadChip and 155 animals genotyped with the Bovine LDv4 panel) were analysed. The LD was evaluated at distances of 25-50 kb, 50-100 kb, 100-500 kb and 0.5-1 Mb. The N was estimated based on 5 past generations. The r values (a measure of LD) were, respectively, .35, .29, .18 and .032 for the distances evaluated. The LD estimates decreased with increasing distance of SNP pairs and LD persisted up to a distance of 100 kb (r = .29). The N was greater in generations 4 and 5 (24 and 30 animals, respectively) and declined drastically after the last generation (12 animals). The results showed high levels of LD and low N , which were probably due to the loss of genetic variability as a consequence of the structure of the Gir population studied.
连锁不平衡（LD）在基因组选择和数量性状基因座（QTL）定位中起着重要作用。本研究调查了针对一岁体重进行选择的吉尔牛的连锁不平衡模式和有效种群大小（N）。为此，分析了173头具有推算基因型的动物（其中18头用Illumina BovineHD BeadChip进行基因分型，155头用牛LDv4芯片进行基因分型）。在25 - 50 kb、50 - 100 kb、100 - 500 kb和0.5 - 1 Mb的距离上评估连锁不平衡。基于过去5代估计有效种群大小（N）。在所评估的距离上，r值（连锁不平衡的一种度量）分别为0.35、0.29、0.18和0.032。连锁不平衡估计值随着单核苷酸多态性（SNP）对之间距离的增加而降低，并且连锁不平衡在100 kb的距离内仍然存在（r = 0.29）。有效种群大小（N）在第4代和第5代较大（分别为24头和30头），在上一代（12头）之后急剧下降。结果表明连锁不平衡水平较高且有效种群大小（N）较低，这可能是由于所研究的吉尔牛种群结构导致遗传变异性丧失的结果。
