1. To help on farm management or participatory approaches to find an official recognition, we are conducting a sociological, historical, ethno-botanical study of the actors, and a parallel genetic study of the varieties/populations in order to assess the ability of farmers networks to conserve and develop genetic diversity through local adaptation and seeds exchanges. Here, we present a case study of an old wheat variety (Rouge de Bordeaux, RB) grown for several generations in different farms under different conditions and farming practices. This old variety (~1880) has recently spread over organic farms in France due to its high “artisanale” bread making quality and good adaptation to organic conditions. On-farm dynamic management of wheat populations in organic agriculture: a way to valorize GxE interactions Material and methods Numerous studies of traditional agricultural systems in the South have shown that the farmers practices for seeds management were the key for local adaptation whilst maintaining the genetic diversity, due to the co-existence in the populations of all evolutionary mechanisms: selection, genetic drift, migration, mutation (Smith et al., 2001 ; Almekinder et al., 2000 ; Louette et al., 1997 ; Bertaud et al., 2001 ; Elias et al., 2001). Hence, this can be described as a dynamic management approach. In industrialized countries, such approaches are usually developped through the cooperation of farmers and breeders and/or researchers, and they might be of a great interest for organic or low input farming systems where the effects of environment and practices combine to produce a large range of contrasted conditions. Yet, these approaches are scarce and they still do not have found a clear position in the seed regulation framework in France. Introduction Introduction Results and discussion Based on the sociological survey, a partial network of seeds exchange was drawn indicating complex and active exchanges, especially for the variety RB (Fig. 1). Phenotypic evaluation in station shows that samples with different origins are significantly different for their early development, their heading time under vernalized conditions and their vernalization requirements (Fig. 2). This is found when comparing the samples means but also the vithin- sample variation. For instance, the within-population strewing of heading date under vernalized conditions ranges from 2 to 10 days depending on the origin of the sample. Heritabilities for heading date under vernalized conditions ranges from 0.71 to 0.87 indicating a large genetic component of the between samples variation. References ! Almekinder C.J.M., de Boef W. & Engels J. (2000) Synthesis between crop conservation and development. In: C Almekinders & W de Boef (Eds), Encouraging Diversity. The conservation and development of plant genetic resources, Intermediate Technology Publications, London, pp330-338. Berthaud J., Clément J.C., Empearire L., Louette D., Pinton F., Sanou J. et al (2001) The role of local level gene flow in enhancing and maintaining genetic diversity. In: Cooper HD, Spillane C, Hodgkin T (Eds) Broadening the genetic diversity of crop production, CABI Publishing in assoication FAO and IPGRI: Rome, Italy pp81-103. Elias M., McKey D., Panaud O., Mc Anstett & Robert T. (2001) Traditional management of cassava morphological and genetic diversity by the Makushi Amerindians (Guyana, South America): perspectives for on-farm conservation of crop genetic resources. Euphytica 120: 143-157. Louette D., Charrier A. & Berthaud J. (1997) In situ conservation of maize in Mexico : genetic diversity and maize seed management in a traditional community. Econ. Bot. 51: 20-38. Smith, M.E., Fernando, C.G. & Gomez, F. (2001) Participatory plant breeding with maize in Mexico and Honduras. Euphytica 122: 551- 565. Goldringer I 1, Galic N 1, Rousselle Y 1, Demeulenaere E 2, Bonneuil C 3, Payement J 4, Berthellot JF 4, Chesneau V 4, Mercier F 4, Ferté H 4, Pommart A 4, Zaharia H 4 1. UMR de Génétique Végétale, INRA Univ. Paris Sud CNRS AgroParisTech, Ferme du Moulon, 91190 Gif sur Yvette, France – 2. ENS, CERES, 24 rue Lhomond, 75005 Paris, France – 3. Centre Koyré, CNRS - EHESS – MNHN, CP 25, 57 rue Cuvier, 75231 Paris cedex 05, France – 4. Réseau Semences Paysannes, Cazalens, 81600 Brens, France Participatory selection in Syria (S Ceccarelli, ICARDA) Seeds samples were collected for about 25 different farmers RB varieties as well as for 4 RB accessions from the Inra collection. In 2006-2007, they were assessed phenotypically in 6 farms and in a research station (Le Moulon). Leaf samples of 20-35 individuals / RB-sample were collected, DNA was extracted and they will be genotyped with a set of “neutral” SSR markers and markers of the VRN1 loci (vernalization response). Phenotypic evaluation - A Pommart experimentation (Alps) Phenotypic evaluation - V Chesneau experimentation (West coast) Fig. 1: Map of seeds exchanges between farmers for the Variety RB These preliminary results show that varieties/populations grown on farm can develop particular traits in response to both environmental conditions ans human practices since very contrasted conditions can be met in organic agriculture, as shown on the pictures (16-20th April 2007). Phenotypic data will be completed with the genotypic data for for 21 “neutral” SSR markers and for VRN1 markers allowing for a deeper analysis of the organisation of genetic diversity in this farmers network. Within-sample phenotypic and genetic diversity, differentiation between samples at both levels will be studied together with the history of the varieties and the farmers practices in order to describe the links between farmers practices and diversity conservation. Phenotypic evaluation - JF Berthellot experimentation (South-West) Phenotypic evaluation - J Payement experimentation (South-West)