Abstract
Labs as guide dogs or sniffer dogs in usage have been introduced into China for more than 20 years. These two types of working dogs own blunt or acute olfactory senses, which have been obtained by artificial selection in relatively closed populations. In order to attain stable olfactory attributes and meet use-oriented demands, Chinese breeders keep doing the same artificial selection. Though olfactory behavior is canine genetic behavior, genotypes of OR genes formed by breeding schemes are largely unknown. Here, we characterized 26 SNPs, 2 deletions, and 2 insertions of 7 OR genes between sniffer dogs and guide dogs in order to find out the candidate alleles associated with working specific traits. The results showed that there were candidate functional SNP alleles in one locus that had statistically severely significant differences between the two subpopulations. Furthermore, the levels of polymorphism were not high in all loci and linkage disequilibrium only happened within one OR gene. Hardy–Weinberg equilibrium (HWE) tests showed that there was a higher ratio not in HWE and lower FST within the two working dog populations. We conclude that artificial selection in working capacities has acted on SNP alleles of OR genes in a dog breed and driven the evolution in compliance with people's intentions though the changes are limited in decades of strategic breeding.
Highlights
Artificial selection has been largely responsible for breedspecific and strain-specific traits of modern dogs [1]
A unique homozygous genotype was presented in 12 SNP loci, while the only heterozygous genotype was found in 2 SNP loci within all Labrador Retriever (Lab)
Except 12 homozygous monogenotype loci, the results revealed that 5 SNP loci were out of Hardy–Weinberg equilibrium (HWE) (P < 0.0005) and 5 SNP loci were in the state of Hardy–Weinberg balance (P > 0.0005) for all Labs. e other eight SNP loci showed either significant departure or no significant deviations from HWE between working populations, while six of the eight SNP loci were in HWE in the collective
Summary
Artificial selection has been largely responsible for breedspecific and strain-specific traits of modern dogs [1]. Compared with early domestication of a dog breed driven by natural factors such as dietary conditions and geographical environments, the recent subpopulation differentiations are more dramatically caused by artificial goal-directed breeding practices, especially during the last two centuries [2]. Straindependent differences of dogs are mainly presented in body size, coat color, and work capacity [3, 4]. Labrador Retriever (Lab) is a traditional waterdog in Newfoundland. During the latter half of the nineteenth century, British breeders had refined and standardized Labs that had become a popular breed because they were famously friendly and exuberant around the world [5–7]. In order to attain stable olfactory attributes and meet use-oriented demands, Labs are bred in relatively closed populations by strict selection [8, 9]
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