Whole genome fine mapping of quantitative trait loci for ultrasound and carcass merit traits in beef cattle.

摘要

Quantitative trait loci (QTL) mapped to large chromosomal regions have limited utility as DNA markers for marker-assisted selection (MAS) and are less informative as a reference for the identification of underlying causative quantitative trait nucleotides (QTN). In this study, whole genome fine mapping of QTL for ultrasound and carcass merit traits in beef cattle was conducted using a greater density of single nucleotide polymorphism (SNP) markers, and SNP markers within the QTL regions associated with the traits were identified. 418 male cattle from 28 sires were used in this study with 9 ultrasound and 7 carcass merit traits that were collected as part of a feedlot trial conducted from 2003 to 2005 at the University of Alberta Kinsella ranch, Canada. Sires and their progeny were genotyped for a total of 4592 SNP markers distributed across all 29 cattle autosomes. Across-family analyses detected 12 QTL for 5 ultrasound traits on 9 chromosomes and 18 QTL for 6 carcass merit traits on 10 chromosomes (P < 0.05). Within-family analyses identified 78 significant QTL for 9 ultrasound and 7 carcass merit traits (P < 0.01). The use of a denser panel of SNP markers allowed fine mapping of QTL to smaller chromosomal regions ranging from 0.6 to 11 cM compared with relatively larger QTL regions of 4-24 cM reported in previous studies. Furthermore, single SNP marker association analyses identified 22 SNP that were significantly associated with 3 ultrasound and 4 carcass merit traits under 12 QTL regions (P < 0.05). These identified SNP markers significantly associated with the traits under the fine mapped QTL regions provide genomic tools for potential application of MAS and a reference to assist with the identification of QTN causing variations in ultrasound and carcass merit traits in beef cattle.