Abstract
A detailed quantitative trait locus (QTL) analysis of growth and fatness data from a three generation experimental cross between Large White (LW) and Meishan (MS) pig breeds was carried out to search for sex × QTL interactions, imprinting effects and multiple linked QTLs. A total of 530 F2 males and 573 F2 females issued from 6 F1 boars and 23 F1 sows were typed for a total of 137 markers covering the entire porcine genome. Nine growth traits and three backfat thickness measurements were analysed. All analyses were performed using line cross regression procedures. A QTL with sex-specific expression was revealed in the proximal region of chromosome 8, although some confusion between herd and sex effects could not be discarded. This previously undetected QTL affected male growth during the fattening period, with a favourable additive effect of the LW allele. The analyses also revealed the presence of two linked QTLs segregating on chromosome 1, affecting growth traits during the post-weaning period. The first QTL, previously detected using a single QTL model, was located at the end of the q arm of chromosome 1 and had a favourable MS allele. The second QTL had a favourable LW allele and was located in the proximal extremity of the q arm of chromosome 1. Suggestive genomic imprinting was found in the distal region of chromosome 9 affecting growth during the fattening period.
Highlights
The interaction term had a very limited effect on the most probable position of the quantitative trait loci (QTL), which was located between SW905 and SWR1101, but QTL effects widely differed between sexes
The sex × QTL interaction on Sus Scrofa chromosome (SSC) 10 was due to differences in additive effects on ABT17, with no effect in males and a favourable effect of the Large White (LW) allele in females
The absence of significant family × QTL interaction in the F2 population analysed tends to indicate that there are no significant differences in the estimated effects for LW and MS alleles passed through different F1 individuals
Summary
Beyond the numerous published genetic maps of the porcine genome, e.g. [4, 12,27,28], systematic searches of quantitative trait loci (QTL) in pigs have been performed during the last years [3,10,17,18,20,23,24,25,29,30,31,32,33,34,36]. [4, 12,27,28], systematic searches of quantitative trait loci (QTL) in pigs have been performed during the last years [3,10,17,18,20,23,24,25,29,30,31,32,33,34,36] These experiments have revealed a number of genome regions affecting quantitative traits of economic importance but, with some exceptions [11,17,18,22], little effort has been invested in searching multiple QTLs in the same linkage group or studying non-Mendelian forms of expression. Neither imprinting effects nor the sex × QTL interaction have been usually studied in QTL analyses
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