Journal of Experimental Botany, Vol 50, 283-290, Copyright © 1999 by Oxford University Press
J Enjalbert, I Goldringer, S Paillard and P Brabant
Studying the heterogeneity in variation of gene frequency among populations
or between generations may be a possible way to detect genomic regions
experiencing selection. In order to evaluate this approach, RFLP markers
were used to compare the allelic frequencies in wheat populations that had
been submitted to natural selection. In 1984, samples of two composite
cross populations were distributed in the French network for dynamic
management of genetic resources. Since then, all the sub-populations have
been cultivated in the same sites with no human selection. The strong
differentiation between populations found for agro-morphological traits
(earliness, resistance to pathogens, ...) provided evidence of their
adaptation to local conditions. The two initial populations and six derived
sub-populations cultivated for 10 years in four contrasted sites were
studied with RFLP markers. Differentiation between sub-populations based on
RFLP diversity was highly significant. Variations on allelic frequencies of
the 30 loci scored were found to be much greater than expected under
genetic drift only. This led us to conclude that selection greatly
influenced the evolution of the populations. Some of the loci clearly
presented a higher differentiation than the others. This might indicate
that they were genetically linked to other loci polymorphic in the
populations and involved in adaptation. However, the effect of one selected
gene on a marker, even located very close to the gene, could not be
predicted with certainty. Hence, though the populations were predominantly
selfing, it seems that initial linkage disequilibriums between markers and
selected genes were not strong enough to control closely the evolution of
allelic frequencies at the markers.Key words: Dynamic
management, wheat, molecular markers, adaptation, natural selection.
ARTICLES
Molecular markers to study genetic drift and selection in wheat populations
Station de Génétique Végétale, INRA/INA-PG UPS, Ferme du Moulon, F-91190 Gif-sur-Yvette, France; INA-PG, 16 rue Claude Bernard, F-65005 Paris, France; Corresponding author e-mail:isa@moulon.inra.fr
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