Quantitative Trait Loci Associated with Egg Traits in F2 Intercross between Golden Montazah and White Leghorn Chickens

M.H.Abdel A’al1, M.M.Iraqi2, M.H.Khalil2, G.M.El-Moghazy1, M.M.El-Atrouny2"


Quantitative trait loci (QTL) affecting age at first egg (AFE), weight at first egg (WFE), 120-days of egg number (EN), egg weight (EW), Hugh unit (HU) and egg shell strength (ESS) were identified in F2 intercross population produced by crossing males of Golden Montazah (M) with females of White Leghorn (L). Phenotypic data for egg traits of 4131 hens were analyzed using multi-traits animal model. For QTL analysis, 1011 hens of F2 were genotyped using 45 genetic markers in nine autosomal linkage groups and Z chromosome and the mixed model including the fixed effects of hatch along with the additive and dominance effects of QTL as random effects was used. The total map length was 1949 cM and a total of 15 significant QTL were detected for egg traits and these QTL were distributed over four distinct regions on five chromosomes (2, 3, 4, 8 and Z). The QTL region on the Z chromosome was large and including QTL for AFW, EW, EN and ESS. The significant QTL were located on chromosomes 2, 4, 8 and Z for WFE at position of 322, 156, 61 and 102 cM; on the chromosomes 3 and Z for AFE at position of 189 and 128 cM, on the chromosomes 4 and Z sex chromosome for EW at position of 191 and 76 cM; on the chromosomes 4 and Z for EN at position of 55 and 89 cM; on the chromosomes 2, 4 and 8 for HU at position of 89, 222, and 18 cM; on Z sex chromosome for ESS at position of 97 cM, respectively. A total of four significant QTL were detected at 5 % chromosome-wise significance level, while a total of 11 significant QTL were detected at 1 % genomic-wise significance level and the total variances explained by QTL were 10.7, 12.2, 18.6, 12.2, 15.3 and 5 % for WFE, AFE, EW, EN, HU and ESS, respectively. The additive effects attributable to QTL explaining 5.4 to 53.0 % for WFE, 1.6 % for AFE, 4.4 to 8.2 % for EN, 3.0 to 6.5 % for EW, -0.6 and -6.2 % for Hu and -55.6 % for ESS of the total phenotypic variance of the F2 population, while the dominance effects attributable to QTL explained 0.3 to 10.5, 4.0, -1.1 to -18.0, -1.6, -3.9 to -5.3 for WFE, AFE, EN, EW and HU, respectively.

Key words

Chickens, QTL, Microsatellite markers, Egg traits, Additive effects, Dominance effects