A genomic scan of porcine reproductive traits reveals possible quantitative trait loci (QTLs) for number of corpora lutea

Abstract

Reproductive traits have low heritabilities, are expressed in only one sex, and are not measurable until sexual maturity (Avalos and Smith, Anim Prod 44:153, 1987). Using traditional methods, selection for reproductive traits is relatively less effective than selecting for growth or carcass traits. Traits most affected by a small number of genes with major effects rather than many genes with small effects are most amenable to MAS. As part of our porcine genome scan to identify quantitative trait loci (QTLs) of economic importance in marker-assisted selective (MAS) breeding programs, we examined 8 reproductive and farrowing traits in the University of Illinois (UI) Meishan x Yorkshire Resource Family. Gilts were genotyped with 119 microsatellite markers (MS) with intervals averaging 24 cM over all 18 porcine autosomes. F-ratios supporting QTL location were calculated by the least squares regression method. Results suggestive of linkage at the 5% genome-wide level were observed for the number of stillborn piglets on Chromosome (Chr) 4 (SSC4) (p-value = 0.0001), corpora lutea on SSC8 (p-value = 0.00027), and gestation length on SSC9 (p-value = 0.00019). Results for additional loci relevant to litter size, number of corpora lutea on SSC15 and 7 (p-value = 0.0029 and 0.0028 at 107 and 150 cM, respectively), gestation length on SSC15 and 1 (p-value = 0.0017 and 0.0069 at 96 and 166 cM, respectively), uterine length on SSC7 and 5 (p-value = 0.0044 and 0.0075 at 148 and 1 cM, respectively) and piglets born per litter on SSC6 (p-value = 0.0075 at 102 cM), were not statistically significant at the 5% genome-wide level. Thus, the use of a linked marker to facilitate selection for reproductive traits has considerable potential. By using linked markers, selection can be applied to both sexes before sexual maturity, making genetic selection considerably more efficient and less costly.

A whole genome scan to detect quantitative trait loci for gestation length and sow maternal ability related traits in a White Duroc × Erhualian F2 resource population

“…According to the human-pig comparative maps, except the Booroola fecundity gene (BMPR1B) which was related with gilt prolificacy at first parturition (Tomas et al, 2006), there are no other genes associated with animal reproduction near the QTL region. The QTL for gestation length on SSC1, 6, 9, 11 and 15 (Wilkie et al, 1999;Casellas et al, 2008) were not observed in this study. This could be explained by different breeds or genetic background of founder animals in tested F 2 resource populations.…”

“…In mice Peripato et al (2002) mapped two QTL for maternal performance for offspring survival on chromosomes 2 and 7. Wilkie et al (1999) detected three QTL on pig chromosomes (SSC)1, 9 and 15 for gestation length in a three-generation Meishan 3 Yorkshire resource population. Casellas et al (2008) identified three QTL for gestation length on SSC6, 8 and 11 in the Iberian 3 Meishan F 2 sows.…”

Detection of quantitative trait loci for teat number and female reproductive traits in Meishan × Large White F2 pigs

“…Five QTL affecting age at puberty have been reported in only two studies (Rohrer et al, 1999;Cassady et al, 2001). Results for ovulation rate are slightly more numerous, as 14 chromosomal regions associated with variations in OR are reported in PiqQTLdb (Rohrer et al, 1999;Wilkie et al, 1999;Cassady et al, 2001;Campbell et al, 2003). Regarding litter size, 12 QTL located on 10 different chromosomes have been reported (Rathje et al, 1997;Cassady et al, 2001;de Koning et al, 2001;Noguera et al, 2006;Tribout et al, 2008), of which only those reported by Noguera et al (2006) reached a genome-wide significance level (P , 0.05).…”

Use of meta-analysis to combine candidate gene association studies: application to study the relationship between the ESR PvuII polymorphism and sow litter size

“…Different linkage relationships may be the reason why estimates vary across populations, although it has been observed that the ESR effect can differ in its magnitude and direction not only across but also within populations [17]. The genome scanning approach had not shown evidence for QTL influencing litter size in the region harbouring the ESR locus on chromosome 1 e.g., [4,13,39,59], but it should be considered that these screenings were of poor power to detect a QTL. The fact that a causative mutation has not been described and made public continues to be the main obstacle to conclude the evidence for the hypothesis of the PvuII polymorphism being a marker of a gene affecting sow litter size [42].…”