Congratulations to our new FdV Doctor Mathieu THOMAS who graduated on November 29th 2011.
Title (french) : "Gestion dynamique à la ferme de l'agrobiodiversité : relation entre la structure des populations de blé tendre et les pratiques humaines".
The development of sustainable management strategies for both wild and cultivated biodiversity is a critical issue particularly because they provide ecosystem services
necessary to the welfare of humanity. In situ conservation approaches allow the continuous adaptation of these resources to environmental changes. Seed exchanges within
and among communities maintains a high level of biodiversity in subsistence farming systems, leading to the dynamic management of agrobiodiversity. Such seed exchange
networks reappear in different forms of social organization in industrialized countries. While these networks have received little attention thus far, these types of systems could
expand their role in the landscape of the conservation of crop diversity.
This interdisciplinary project at the interface between population genetics and ethnology sought to evaluate the relevance of such a model in France. To this end, we characteri-
zed the structure of the genetic and phenotypic diversity of population-varieties of bread wheat (Triticum aestivum) exchanged within a network of farmers. The structure of these
populations are simultaneously shaped by human action and environmental conditions; we were interested in identifying and prioritizing the impact of different evolutionary
forces acting on this in situ dynamic system.
The research focused on a population-variety (Rouge de Bordeaux, RDB) and a mixture of landraces (Mélange de Touselles, MDT), each grown for several years by about twenty
farmers located in different regions. Interviews with farmers provided information about seed diffusion, cultural practices and pedo-climatic characteristics of the different farms.
A controlled experiment allowed us to compare seed samples from farmers' and from the National Center of Genetic Resources. Measurements were performed at the phenotypic
level (earliness of heading, plant size, kernels weight, number of kernel per ear) and at the genotypic level (19 microsatellite markers and four markers in two genes involved in the
determination of flowering).
The history of seed exchanges among farmers was able to explain the genetic structure of the studied RDB populations. Two independent pathways of seed diffusion were identi-
fied, and corresponded to the observed genetic structure. The spatio-temporal monitoring of changes in the MDT mixture revealed the ability to maintain genetic diversity at the
metapopulation scale with genetic and phenotypic differentiation among populations. These results show the ability of the mixture to adapt quickly to new environments through
rapid evolution of the component varieties.
Both studies showed that : (i) on-farm management of mixtures of varieties and also population-varieties of wheat have a composite and complex genetic structure, which
is important to take into account in management strategies, (ii) the observed diversity of practices interacting with contrast environments submit populations to genetic drift,
migration or selection in very different ways depending on the context, (iii) distributed and decentralized systems have the emergent property of maintaining global diversity. By
maintaining this evolutionary process, structured systems in seed exchange networks are relevant social organizations to the management of agrobiodiversity because they allow
the cultivated populations to adapt quickly, ensuring the sustainability of these resources and addressing future environmental and societal changes.
M. Doyle McKey
M. Alain Franc
Mme Isabelle Olivieri
Mme Isabelle Bonnin
M. Thierry Robert
Mme Isabelle Goldringer
M. Christophe Bonneuil