| Ascites is an energy metabolism-related genetic disorder in broiler breeders. The maternal effects on ascites were studied using the chicken FSHbeta gene. Two novel single nucleotide polymorphisms (SNPs), +134C>T and +336A>C, were detected in Intron 1 in divergent ascites lines. Across these SNPs, genotype frequencies were determined in 357 and 192 birds of four breeds and four lines. Ascites resistant line (Res), which laid more eggs, had more birds with +134T/T +336C/C homozygous genotype than susceptible line (Sus). These two SNPs unseen in layers and Red Jungle Fowl were introduced into meat-type birds by Athens-Canadian.;A further analysis of genotype and phenotype association was performed to determine intronic SNPs and ascites selection effects on egg production (EP), final body weight (BW), and reproductive organ traits. Homozygote for +134T/T +336C/C was associated with ascites resistance, lower BW, earlier age of first egg (AFE), and higher EP during 17 wks of EP. In contrast, homozygote for 134C/C +336A/A possessed ascites susceptibility, medium BW, and relatively higher EP beyond 17 wks of EP. Heterozygote produced the fewest eggs with birds having higher BW. Compared with the control line, Res laid more before 17 wks of EP and Sus laid fewer thereafter. Sus had higher BW but less stroma and oviduct weight. Therefore, ascites resistance selection generated a larger pressure on the early and peak EP, but ascites susceptible selection had a larger pressure on the late EP, which generated a worse reproduction composition. This association study showed that two SNPs in Intron 1 exhibit an age-related interaction of growth and reproduction.;In the proximal promoter region, we identified two palindromic motifs containing three SNPs (-251T>C, -235G>- and -237G>-). These could account for an evolutionary process from wild type to domestic fowl. Our results showed that the linkage of +134C/C +336C/C genotype with -251C/C in a line selected for virus was not found in ascites lines. Variant selection pressures influenced different intronic genotypes, which may be linked to promoter region.;This work provides a genome basis for further studies investigating promoter-associated chromatin methylation in reproduction aging, and epistasis effect of intron variants on quantitative traits. |
