- V — Gestion Dynamique des Ressources Génétiques Dynamic Management of Genetic Resources
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Diversité génétique et dynamique des formes adventices de riz de camargue
Genetic diversity and population dynamics of weedy rice in Camargue area
Genetics Selection Evolution volume 33, Article number: S425 (2001)
Résumé
À côté des riz adventices des régions tropicales qui résultent d’introgressions variées avec les riz sauvages, de nouvelles formes ont émergé plus récemment et présentent aussi de nombreux attributs des formes typiquement spontanées d’O. rufipogon (égrenage, dormance, aristation, pigmentation des organes). Cette apparition concerne de nombreuses régions du monde pratiquant la riziculture intensive avec semis direct et situées le plus souvent en dehors de la zone de répartition géographique d’O. rufipogon. Différents échantillons d’adventices provenant de Camargue ont été analysés pour 15 marqueurs microsatellites comparativement à une collection représentative de 145 variétés de riz cultivé d’origine asiatique. La diversité génétique des riz adventices est cohérente avec la structuration d’O. sativa qui est organisée en deux groupes principaux indica et japonica. Les adventices de Camargue montrent une diversité plus importante que les variétés locales (japonica tempérées) ainsi que la présence d’allèles originaux ou plus caractéristiques des variétés indica. Cette diversité est totalement indépendante des variétés cultivées localement. La structure génétique de ces formes ne semble pas liée à des flux de gènes avec les variétés dont elles sont isolées grâce à une précocité plus forte mais à une dynamique autonome de ces formes due à des possibilités de conservation (dormance) et de dissémination des graines (égrenage). Le rôle des croisements éloignés (indica × japonica) sur la structure et l’expression du génome pourrait être une explication possible à ce processus.
Abstract
Weedy rice have long been known, particularly in tropical areas, as the result of introgressions between wild and cultivated forms. More recently, rice fields have been frequently invaded by new weedy forms in temperate regions where wild forms were never reported. These plants show many traits similar to true wild O. rufipogon (shattering, dormancy, awning, organ pigmentation). Their occurrence concerns many parts of the world practicing intensive rice-growing with direct seeding. Samples of weeds from Camargue have been analyzed with 15 microsatellite markers in comparison to a representative collection of 145 Asian rice varieties. Diversity of weedy rice is in agreement with the genetic structure of O. sativa mainly organized in two main groups of varieties, indica and japonica. Weeds from Camargue showed a greater diversity than Mediterranean varieties (temperate japonica) as well as the presence of original alleles or alleles more typical of indica varieties. Genetic structure of weed stands appeared more probably the consequence of a predominantly autonomous dynamics allowed by seed conservation and dissemination than the result of gene flow with varieties from which they are isolated by a much greater precocity. These results suggested that distant crosses between indica and japonica varieties and their effect on genome structure and expression could be a relevant explanation to this “weediness” process.
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Bres-Patry, C., Bangratz, M. & Ghesquière, A. Diversité génétique et dynamique des formes adventices de riz de camargue. Genet Sel Evol 33 (Suppl 1), S425 (2001). https://doi.org/10.1186/BF03500893
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DOI: https://doi.org/10.1186/BF03500893