Résumé
Cultivated plants have been molded by human-induced selection, including
manipulations of the mating system in the twentieth century. How these
manipulations have affected realized parameters of the mating system in
freely evolving cultivated populations is of interest for optimizing the
management of breeding populations, predicting the fate of escaped
populations and providing material for experimental evolution studies. To
produce modern varieties of sunflower (Helianthus annuus L.),
self-incompatibility has been broken, recurrent generations of selfing
have been performed and male sterility has been introduced. Populations
deriving from hybrid-F1 varieties are gynodioecious because of the
segregation of a nuclear restorer of male fertility. Using both phenotypic
and genotypic data at 11 microsatellite loci, we analyzed the
consanguinity status of plants of the first three generations of such a
population and estimated parameters related to the mating system. We
showed that the resource reallocation to seed in male-sterile individuals
was not significant, that inbreeding depression on seed production
averaged 15–20% and that cultivated sunflower had acquired a mixed-mating
system, with ~50% of selfing among the hermaphrodites. According to
theoretical models, the female advantage and the inbreeding depression at
the seed production stage were too low to allow the persistence of male
sterility. We discuss our methods of parameter estimation and the
potential of such study system in evolutionary biology.