Integration of QTL Detection of Growth Traits and Association Study for Chicken Chromosome 4

Abstract

Quantitative trait locus (QTL) mapping opens a way for breeders to manipulate quantitative trait genes. The objective of this study is to detect the QTL related to growth performance in local breeds of chicken. A cross between three genetically different chicken’ breeds was used to produce two generations populations. Data of 954 chicks produced during the auxiliary two generations of different crosses (S♂xF♀, S♂xA♀, SF♂xSF♀, SA♂xSA♀, SF♂xSA♀ and SA♂xSF♀) in such a way the genetic homogeneity from G0 to G2 recombinant populations has been considered. These populations were used for detection and localization of QTL related to the growth traits; body weight (BW), growth rate (GR), and average daily gain (ADG). A number of 25 microsatellite markers belong to chicken chromosome 4 (GGA4) have been genotyped, and the regression interval mapping approach was used to identify QTL. There was a statistical evidence for QTL on GGA4 for BW at 8 and 12 weeks of age, whereas one QTL exceeded the significant threshold for the trait of BW at 8 weeks of age. All of three QTL effects identified on GGA4 had their maximum test statistic in the region between 134-154 cM. In addition, most of significant markers (MCW0390, MCW0393, MCW0397, MCW0409, MCW410 and UMA0038) were associated with growth traits at all chicken ages. Although, the polymorphism information content (PIC) obtained over all microsatellite markers was 46%, that around 82% went to UMA0038 locus. Two private alleles were found for markers MCW0405 and MCW0409 with allele frequency around 0.025 in G1 and G2 respectively. Additionally, Chi-square test was used to investigate the deviation of loci from Hardy-Weinberg equilibrium individually, and four microsatellite markers (MCW0395, ADL0266, MCW0400 and UMA0038) were not in genetic equilibrium. I The obtained small value of FST (ranged between 0.001 to 0.019) may reflect generous genetic differentiation.