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Many QTLs with minor additive effects are associated with a large difference in growth between two selection lines in chickens

Published online by Cambridge University Press:  15 December 2005

LINA JACOBSSON ,
HEE-BOK PARK ,
PER WAHLBERG ,
ROBERT FREDRIKSSON ,
MIGUEL PEREZ-ENCISO ,
PAUL B. SIEGEL  and
LEIF ANDERSSON
LINA JACOBSSON
Affiliation:
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, BMC, SE-75124 Uppsala, Sweden
HEE-BOK PARK
Affiliation:
Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, SE-75124 Uppsala, Sweden
PER WAHLBERG
Affiliation:
Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, SE-75124 Uppsala, Sweden
ROBERT FREDRIKSSON
Affiliation:
Department of Neuroscience, Uppsala University, BMC, SE-75124 Uppsala, Sweden
MIGUEL PEREZ-ENCISO
Affiliation:
Institut Català de Recerca i Estudis Avançats, 08010 Barcelona, Spain Department de Ciència Animal i del Aliments, Facultat de Veterinária, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
PAUL B. SIEGEL
Affiliation:
Virginia Polytechnic Institute and State University, Department of Animal and Poultry Sciences, Blacksburg, VA 2406-0300, USA
LEIF ANDERSSON
Affiliation:
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, BMC, SE-75124 Uppsala, Sweden Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, SE-75124 Uppsala, Sweden
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Abstract

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Two growth-selected lines in chickens have been developed from a single founder population by divergent selection for body weight at 56 days of age. After more than 40 generations of selection they show a nine-fold difference in body weight at selection age and large differences in growth rate, appetite, fat deposition and metabolic characteristics. We have generated a large intercross between these lines comprising more than 800 F2 birds. QTL mapping revealed 13 loci affecting growth. The most striking observation was that the allele in the high weight line in all cases was associated with enhanced growth, but each locus explained only a small proportion of the phenotypic variance using a standard QTL model (1·3–3·1%). This result is in sharp contrast to our previous study where we reported that the two-fold difference in adult body size between the red junglefowl and White Leghorn domestic chickens is explained by a small number of QTLs with large additive effects. Furthermore, no QTLs for anorexia or antibody response were detected despite large differences for these traits between the founder lines. The result is an excellent example where a large phenotypic difference between populations occurs in the apparent absence of any single locus with large phenotypic effects. The study underscores the need for powerful experimental designs in genetic studies of multifactorial traits. No QTL at all would have reached genome-wide significance using a less powerful design (e.g. approx. 200 F2 individuals) regardless of the nine-fold phenotypic difference between the founder lines for the selected trait.

Type
Research Article
Information
Genetics Research , Volume 86 , Issue 2 , October 2005 , pp. 115 - 125
Copyright
© 2005 Cambridge University Press