Abstract
Bi-directional selection for increased and decreased 56-day body weights (BW56) has been applied to two lines of White Plymouth Rock chickens—the Virginia high (HWS) and low (LWS) body weight lines. Correlated responses have been observed, including negative effects on traits related to fitness. Here, we use high and low body weight as proxies for fitness. On a genome-wide level, relaxed lines (HWR, LWR) bred from HWS and LWS purged some genetic variants in the selected lines. Whole-genome re-sequencing was here used to identify individual loci where alleles that accumulated during directional selection were purged when selection was relaxed. In total, 11 loci with significant purging signals were identified, five in the low (LW) and six in the high (HW) body weight lineages. Associations between purged haplotypes in these loci and BW56 were tested in an advanced intercross line (AIL). Two loci with purging signals and haplotype associations to BW56 are particularly interesting for further functional characterization, one locus on chromosome 6 in the LW covering the sour-taste receptor gene PKD2L1, a functional candidate gene for the decreased appetite observed in the LWS and a locus on chromosome 20 in the HW containing a skeletal muscle hypertrophy gene, DNTTIP1.
Highlights
The domestication of plants and animals has, for thousands of years, played a pivotal role in the development of human societies [1]
Based on changes in haplotype-frequencies after relaxation of selection in the Virginia body weight chicken lines, we aimed to identify individual purging loci and the haplotypes segregating in them using whole-genome re-sequencing and 60 K chicken single nucleotide polymorphism (SNP)
These fulfill the aims of this study of identifying the individual loci contributing to the purging and highlight those most likely involved in the negatively correlated selection responses on body weight and fitness related traits earlier observed in this population [12,13,15,24]
Summary
The domestication of plants and animals has, for thousands of years, played a pivotal role in the development of human societies [1]. During domestication, imposed artificial selection has been used to change traits of interest. Domestication involves changes whereby the breeding and care of plants and animals are directly or indirectly controlled by humans [3] and is a continuing process that may be viewed historically in a geographical and time context [1]. The recent (in the context of time) rediscovery of Mendelism and technological developments have resulted in the worldwide development of chickens bred for egg production or body size. This delineation has occurred because of the negative genetic correlation between them, resulting in competition in the allocation of resources [6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
