Genetic diversity and gene flow among pearl millet crop/weed complex: A case study

Mariac Cédric, Robert Thierry, Allinne Clémentine, Remigereau Marie-Stanislas, Luxereau Anne, Tidjani Moussa, Seyni O., Bezançon Gilles, Pham Jean Louis, Sarr Amadou. 2006. Genetic diversity and gene flow among pearl millet crop/weed complex: A case study. Theoretical and Applied Genetics, 113 (6) : 1003-1014.

Résumé : Weedy plants with intermediate (domesticated × wild) phenotypes occur in most pearl millet fields in West Africa, even in the absence of wild populations. They are usually found, in high numbers, both inside and outside of drills. Questions pertaining to the evolutionary dynamics of diversity within the pearl millet complex (domesticated–weedy–wild forms) were addressed in this study. The diversity of the different components of this complex sampled in two pearl millet fields in two villages of southwestern Niger was assessed at both molecular (AFLP) and morphological levels. Results show that, in both fields, weedy plants found outside of drills are morphologically distinct from weedy plants found inside drills, despite their close similarity at AFLP markers. The data suggest some introgression from the wild to the weedy population but nevertheless that the gene flow between the parapatric wild and domesticated populations is very low. This challenges the traditional view that regular hybridization between domesticated and wild pearl millets explains the abundance of these weedy plants despite farmers' seed selection. The level of genetic differentiation between fields from the two villages was low when considering domesticated and weedy plants. This could be explained by high gene flow resulting from substantial seed exchanges between farmers. The fact that it is very difficult for farmers to keep their own selected seeds, and the consequent substantial seed exchanges between them, is probably the main factor accounting for the maintenance and dispersal of weedy pearl millets in the region, even in areas where no wild forms have been observed.

Mots-clés libres : Pearl millet, Gene flow, Wild population, Seed exchange, Genetic differentiation, Soil seed bank, Genetic diversity, Pollen flow

Classification Agris : H60 - Mauvaises herbes et désherbage
F30 - Génétique et amélioration des plantes
F01 - Culture des plantes

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

• Mariac Cédric, IRD (FRA)
• Robert Thierry, Université de Paris-Sud (FRA)
• Allinne Clémentine, Université de Paris-Sud (FRA)
• Remigereau Marie-Stanislas, Université de Paris-Sud (FRA)
• Luxereau Anne, MNHN (FRA)
• Tidjani Moussa, IRD (NER)
• Seyni O., INRAN (NER)
• Bezançon Gilles, IRD (FRA)
• Pham Jean Louis, IRD (FRA)
• Sarr Amadou, IRD (SEN)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/580470/)

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