marker-assisted selection in wheat - ictsd

Chapter 11 – Marker-assisted selection in poultry 191Table 2Association of candidate genes with quantitative traits in poultryTrait Chromosomes 1 Gene symbols ReferencesAge at first egg 1,2,3 GH, NPY, ODC Feng et al., 1997; Dunn et al., 2004;Parsanejad et al., 2004Disease resistance (E. coli) 16 MHC1, MHC4, TAP2 Yonash et al., 1999Disease resistance (MD 2 ) 1,NK GH, LY6E Kuhnlein et al., 1997; Liu et al., 2001a,band 2003Disease resistance (Sal 3 ) 4,6,7,16,19,1,17,NKTNC, PSAP, NRAMP1 4 ,MHC1,CASP1, IAP1, TLR4,TLR5Double yolked eggs 10 GNRHR Dunn et al., 2004Hu et al., 1997; Lamont et al., 2002;Leveque et al. 2003; Liu and Lamont,2003; Iqbal et al., 2005Egg production Z,1,20 GHR, GH, PEPCK Feng et al., 1997; Kuhnlein et al., 1997;Parsanejad et al., 2003Egg weight 1 IGF1 Nagaraja et al., 2000Eggshell quality 1,3,20 IGF1, ODC, PEPCK Nagaraja et al., 2000; Parsanejad et al.,2003, 2004Body fat 1,1,5,Z GH, IGF1, TGFβ3, GHR Feng et al., 1998; Fotouhi et al., 1993; Liet al., 2003; Zhou et al., 2005Feed efficiency 3,20 ODC, PEPCK Parsanejad et al., 2003 and 2004Body weight/carcass quality 1,3,5,Z,1,1,1 IGF1, ODC, TGFβ3, GHR,APOA2, PIT1Organ weight (spleen) 3,5,32 TGFβ2, TGFβ3, TGFβ4 5 Li et al., 2003Feng et al., 1998; Li et al., 2003; Jiang etal., 2004; Parsanejad et al., 2004; Li et al.,2005; Zhou et al., 2005Skeletal traits 1,3,5,32 IGF1, TGFβ2, TGFβ3, TGFβ4 5 Li et al., 2003; Zhou et al., 20051NK = gene has not yet been assigned to a chromosome.2Marek’s Disease.3Salmonellosis.4Now known as Slc11a1.5TGFβ4 in the paper is now known to be TGFβ1.safety. For production traits such as growthand egg numbers, breeders make sufficientprogress using traditional selectionmethods, and they expect little improvementfrom MAS for such traits unlessmarkers can be used to increase the accuracyof selection. Nonetheless, among breedersof broiler stock there is interest in markersfor traits that are difficult to measure suchas feed efficiency and meat quality in additionto disease resistance.Potential for MAS in chickenThe technical aspects and potentialimplications of implementing MAS inlivestock are discussed in Chapter 10and Dekkers (2004), and van der Beekand van Arendonk (1996) evaluated thetechnical aspects of MAS in poultrybreeding. A review of the potential of MASin poultry is provided by Muir (2003) butthis includes many of the technical issuesthat are common across livestock species.This chapter therefore focuses on poultryspecificissues, and readers are referredto Chapter 10 or Muir (2003) for a morecomprehensive overview of applicationsand limitations of MAS.Muir (2003) identified two cases whereMAS could increase the selection intensityin poultry breeding: (i) traits that are measuredlater in life or are costly to measure(such as egg production and feed efficiencyfor broiler breeders); and (ii) selectionwithin full-sib families for sex-limitedtraits (e.g. male chicks for egg production).Accuracy of selection can also be improvedvia MAS when selecting between full-sibfamilies for sex-limited traits and traits thatcannot be measured directly on one or both