| Issue |
Genet. Sel. Evol.
Volume 33, Number 1, January-February 2001
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|---|---|---|
| Page(s) | 17 - 38 | |
| DOI | https://doi.org/10.1051/gse:2001100 | |
Genet. Sel. Evol. 33 (2001) 17-38
Marker assisted selection for the improvement of two antagonistic traits under mixed inheritance
Etienne Verriera, ba Station de génétique quantitative et appliquée, Institut national de la recherche agronomique, 78352 Jouy-en-Josas Cedex, France
b Département des sciences animales, INA Paris-Grignon, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
(Received 7 January 2000; accepted 4 October 2000)
Abstract
A Monte Carlo simulation was used to investigate the potential of
Marker Assisted Selection (MAS) in a multiple-trait situation. Only
additive effects were considered. The base population was assumed to
be in linkage equilibrium and, next, the population was managed over
15 discrete generations, 10 males and 50 females were chosen out of the
100 candidates of each sex. Performance for two traits was simulated with
an overall heritability of a given trait equal to 0.25 or 0.10 and
the overall genetic correlation between traits was generally equal to
-0.4 except in one case where it was equal to 0. The model involved
one biallelic QTL, accounting for 10 or 
of the genetic variance of a given
trait, plus polygenes. Initial allelic frequencies at the QTL were generally equal
to 0.5 but in one case were equal to 0.1 and 0.9. A marker with 120
different alleles in the 60 founder parents was simulated in the
vicinity of the QTL. Two values of the recombination rate between these
two loci were considered, 0.10 and 0.02. The genetic evaluation was
based on a multiple-trait BLUP animal model, accounting (MAS) or
not (conventional BLUP) for marker information. Two sets of
simulations were run: (1) a "missing data"case, with males having no
record for one of the traits, and (2) a "secondary trait"case, with
one trait having a weight in the aggregate genotype 4 times less than
the other trait and the QTL acting only on this secondary trait. In
the first set, evaluation methods were found to mainly affect the
accuracy of overall genetic values prediction for the trait with
missing data. In comparison with BLUP, MAS led to an extra overall
genetic response for the trait with missing data, which was strongly
penalised under the conventional BLUP, and to a deficit in response for
the other trait. This more balanced evolution of the two traits was
obtained, however, at the expense of the long-term overall cumulated
response for the aggregate genotype, which was 1 to 
lower than the
one obtained under the conventional BLUP. In the second set of
simulation, in the case of low initial frequency (0.1) of the QTL
allele favourable to the secondary trait, MAS was found to be
substantially more efficient to avoid losing this allele than BLUP
only when the QTL had a large effect and the marker was close. More
benefits should be expected from MAS with more specific applications, such
as early selection of animals, or by applying dynamic procedures i.e.
letting the respective weights to QTL and polygenic values in the selection criterion
vary across generation.
Key words: marker assisted selection / genetic response / mixed model methodology
Correspondence and reprints: E. Verrier
e-mail: verrier@inapg.inra.fr
© INRA, EDP Sciences 2001