Résumé
Since the domestication of crop species, humans have derived specific
varieties for particular uses, and shaped the genetic diversity of these
varieties. Here, using an interdisciplinary approach combining ethnobotany
and population genetics, we document the within-variety genetic structure
of a population-variety of bread wheat (Triticum aestivum L.) in relation
to farmers practices to decipher their contribution to crop species
evolution. Using 19 microsatellites markers, we conducted two
complementary graph theory-based methods to analyze population structure
and gene flow among 19 sub-populations of a single population-variety
(Rouge de Bordeaux, RDB). The ethnobotany approach allowed us to determine
the RDB history including diffusion and reproduction events. We found that
the complex genetic structure among the RDB sub-populations is highly
consistent with the structure of the seed diffusion and reproduction
network drawn based on the ethnobotanical study. This structure
highlighted the key role of the farmer-led seed diffusion through founder
effects, selection and genetic drift due to human practices. An important
result is that the genetic diversity conserved on farm is complementary to
that found in the genebank indicating that both systems are required for a
more efficient crop diversity conservation.