Abstract #M70

# M70
Recombination rates in layer chickens.
Zi-Qing Weng*1, Anna Wolc1,2, Rohan L. Fernando1, Jack C. M. Dekkers1, Jesus Arango2, Petek Settar2, Janet E. Fulton2, Neil P. O’Sullivan2, Dorian J. Garrcik1, 1Department of Animal Science, Iowa State University, Ames, IA, 2Hy-Line International, Dallas Center, IA.

Recombination events, which occur during meiosis, vary in frequency across chromosomes, and among individuals. Recombinations are more common in certain genomic locations known as hotspots and these are controlled by genes. The objective of this study was to assess recombination events across the genome, and identify quantitative trait loci (QTL) that influence recombination frequency in white and brown layer chickens. This study included 1,200 white layers hatched between 2006 and 2012, genotyped with a 600K single nucleotide polymorphisms (SNP) panel, and 5,108 brown layers hatched between 2003 and 2011, genotyped with a 40K SNP panel. FImpute was used to impute missing genotypes. After quality control, 173,224 and 23,098 segregating SNPs remained. There were 492 half-sib families in white layers averaging 3.0 ± 3.0 birds, and 1717 half-sib families averaging 5.4 ± 4.9 brown layer birds. Recombinations were identified within half-sib families using LINKPHASE. Total recombination rates within each 1-Mb window was calculated across 28 chromosomes (Chr). Windows with recombination rates greater than 0.03 (≥1.5 SD from the mean) were considered to be recombination hotspots, while those with no recombinations were cold-spots. Genome-wide recombination numbers of parents were analyzed in a weighted BayesB model. Windows that explained >1% genetic variance were considered to harbor QTL. There were 14,746, and 230,701 recombination events detected in white layers and brown layers, respectively. There were 163 and 281 windows with hotspots detected in white and brown layers, respectively, of which 66 were in common. There were 48 common cold-spots in these 2 breeds. Genome-wide recombination number (GRN) differed by breed and sex. White layers (10.9 ± 4.1) had smaller GRN than brown layers (24.1 ± 3.9). In white layers, females (13.6 ± 3.7) had higher GRN than males (9.3 ± 3.5) but in brown layers GRN were similar in females (24.2 ± 4.2) and males (23.9 ± 3.4). A total of 14 and 6 significant windows, which harbor candidate genes influencing genome-wide recombination, were detected in the 2 breeds. No common QTL windows were found in the 2 breeds. Sample size, marker density, inbreeding level and population structure lead to differences in detection of recombination events and QTL in the 2 breeds.

Key Words: recombination, layer chicken