Quantitative Trait Loci Mapping for External Egg Traits in F₂ Chickens

Abstract

Quantitative trait locus (QTL) mapping of external egg traits in chickens was carried out with 143 microsatellite markers using 388 F 2 hens obtained from an intercross of a Japanese Large Game (Oh-Shamo) male and three White Leghorn females. External egg traits, such as the weight and length of eggs and the weight, thickness, strength, and color of eggshells were measured at three different stages of egg production, i.e. early, middle, and late stages. QTL analyses revealed 10 significant and three suggestive QTLs with main effects on external egg traits on chromosomes 1, 2, 4, 5, 8, 10, 11, 12, 17, and Z. The QTL alleles derived from Oh-Shamo, one of the indigenous Japanese breeds, uniquely increased most external egg traits, whereas some QTL alleles had opposite effects on phenotypic differences between Oh-Shamo and White Leghorn. The QTLs detected accounted for 3.09-15.39% of the phenotypic variances. Although the QTLs on chromosomes 5, 8, and Z were found throughout all three stages, the others were identified at only one or two stages. Epistatic QTLs for external egg traits were not detected in the present study. The age-related changes of our main-effect QTLs illustrate one aspect of the complex genetic basis of external egg traits.

Characteristics of Egg-related Traits in the Onagadori (Japanese Extremely Long Tail) Breed of Chickens

“…The differences observed in PC2, PC3, and PC4 indicate that Onagadori eggs have apparently different features from those of the White Leghorn in eggshell-related traits and the volume of the whole egg and albumen. Thus, the Onagadori will be a useful material for analyzing genetic loci affecting the variation of these egg-related traits as in the case of the Oh-Shamo (Tsudzuki et al, 2007;Goto et al, 2011Goto et al, , 2014aGoto et al, , 2014bYoshida et al, 2013). The plural traits in the same principal component might be controlled partially by the same genetic basis.…”

“…AH and YH were measured using an egg quality meter (Fujihira Industry). The ABS digital caliper (Nakamura Mfg., Nagano, Japan) was used for LTA, STA, YL, and YS measurement as described in Goto et al (2014aGoto et al ( , 2014b. We found only one soft shell egg laid by Onagadori and excluded it from the analysis.…”

“…In fact, microsatellite analyses revealed that they mostly show a large genetic distance when compared with foreign breeds (Osman et al, 2006). In recent years, many quantitative trait loci (QTLs) for growth-, meat-, and egg-related traits were identified using some native Japanese chicken breeds Fujinaka, 2001a, 2001b;Tsudzuki et al, 2007;Uemoto et al, 2009Uemoto et al, , 2011Goto et al, 2011Goto et al, , 2014aGoto et al, , 2014bRikimaru et al, 2011;Yoshida et al, 2013), which suggests that native Japanese chickens are valuable genetic resources for understanding genetic architecture underlying the phenotypic traits.…”

Genetic Mapping of Quantitative Trait Loci for Egg Production and Egg Quality Traits in Chickens: a Review

“…For external egg traits, main-effect QTLs were found in 13 QTL regions, with one located on each of chromosomes 1, 2, 4, 8, 10, 11, 12, and 17, two located on chromosome 5, and three located on the Z chromosome (Goto et al, 2014a). For internal egg traits, main-effect QTLs were discovered in 15 QTL regions, with one located on each of chromosomes 2, 3,4,5,6,7,8,9,15, and 27, two located on Z chromosome, and three located on chromosome 1 (Goto et al, 2014b).…”

“…Epistatic QTLs were detected for egg production and internal egg traits (Goto et al, 2011(Goto et al, , 2014b, which are classified into two types. The first epistatic QTL type was those QTLs with both main and interaction effects, shown by dark gray ellipses in Fig.…”