Identification of QTL with effects on intramuscular fat content and fatty acid composition in a Duroc x Large White cross.
BACKGROUND
Improving pork quality can be done by increasing intramuscular fat (IMF) content. This trait is influenced by quantitative trait loci (QTL) sought out in different pig populations. Considering the high IMF content observed in the Duroc pig, it was appealing to determine whether favourable alleles at a major gene or QTL could be found. The detection was performed in an experimental F2 Duroc x Large White population first by segregation analysis, then by QTL mapping using additional molecular information.


RESULTS
Segregation analysis provided evidence for a major gene, with a recessive Duroc allele increasing IMF by 1.8% in Duroc homozygous pigs. However, results depended on whether data were normalised or not. After Box-Cox transformation, likelihood ratio was indeed 12 times lower and no longer significant. The QTL detection results were partly consistent with the segregation analysis. Three QTL significant at the chromosome wide level were evidenced. Two QTL, located on chromosomes 13 and 15, showed a high IMF Duroc recessive allele with an overall effect slightly lower than that expected from segregation analysis (+0.4 g/100 g muscle). The third QTL was located on chromosome 1, with a dominant Large White allele inducing high IMF content (+0.5 g/100 g muscle). Additional QTL were detected for muscular fatty acid composition.


CONCLUSIONS
The study presented results from two complementary approaches, a segregation analysis and a QTL detection, to seek out genes involved in the higher IMF content observed in the Duroc population. Discrepancies between both methods might be partially explained by the existence of at least two QTL with similar characteristics located on two different chromosomes for which different boars were heterozygous. The favourable and dominant allele detected in the Large White population was unexpected. Obviously, in both populations, the favourable alleles inducing high IMF content were not fixed and improving IMF by fixing favourable alleles using markers can then be applied both in Duroc and LW populations. With QTL affecting fatty acid composition, combining an increase of IMF content enhancing monounsaturated fatty acid percentage would be of great interest.
Sanchez
Marie-Pierre
MP
INRA, UR337 Station de génétique quantitative et appliquée, F-78350 Jouy-en-Josas, France. sanchez@jouy.inra.fr
Iannuccelli
Nathalie
N
Basso
Benjamin
B
Bidanel
Jean-Pierre
JP
Billon
Yvon
Y
Gandemer
Gilles
G
Gilbert
Hélène
H
Larzul
Catherine
C
Legault
Christian
C
Riquet
Juliette
J
Milan
Denis
D
Le Roy
Pascale
P
D000818:Animals; D003433:Crosses, Genetic; D004041:Dietary Fats / Q000032:analysis*; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D005819:Genetic Markers; D008297:Male; D008460:Meat / Q000032:analysis*; D009132:Muscles / Q000737:chemistry*; D040641:Quantitative Trait Loci; D034421:Sus scrofa / Q000235:genetics*
D004041:Dietary Fats; D005227:Fatty Acids; D005819:Genetic Markers
Mamm Genome. 2001 Apr;12(4):299-304
11309662
Meat Sci. 2003 Jul;64(3):219-37
22063008
Hum Hered. 1971;21(6):523-42
5149961
Am J Hum Genet. 1986 Feb;38(2):228-34
3946424
J Anim Sci. 1999 Apr;77(4):846-52
10328348
J Anim Sci. 1992 Jul;70(7):2030-7
1644675
Biochem Biophys Res Commun. 1998 Aug 28;249(3):713-8
9731203
Anim Genet. 2006 Aug;37(4):342-7
16879343
J Anim Sci. 2005 Jul;83(7):1481-93
15956455
Meat Sci. 1999 Sep;53(1):59-65
22062933
Biometrics. 1976 Sep;32(3):695-9
963179
Anim Genet. 2004 Jun;35(3):238-41
15147398
J Lipid Res. 1964 Oct;5:600-8
14221106
J Anim Sci. 2005 Feb;83(2):308-15
15644501
Meat Sci. 1991;29(4):295-307
22061434
J Appl Genet. 2002;43(1):69-83
12084972
Anim Genet. 2006 Apr;37(2):113-20
16573525
Anim Genet. 2006 Feb;37(1):17-27
16441291
J Biol Chem. 1957 May;226(1):497-509
13428781
J Anim Sci. 2003 Dec;81(12):2938-49
14677848
Obes Res. 2004 Dec;12(12):1981-94
15687400
Mamm Genome. 2001 Aug;12(8):637-45
11471059
Genet Sel Evol. 2003 Jul-Aug;35(4):385-402
12927073
J Anim Sci. 2006 May;84(5):1083-92
16612010
Mamm Genome. 2003 Sep;14(9):650-6
14629115
J Anim Sci. 2000 May;78(5):1391-2
10834598
Mamm Genome. 2005 Oct;16(10):792-800
16261421
Meat Sci. 1999 Sep;53(1):67-72
22062934
Genetics. 1997 Feb;145(2):395-408
9071593