Résumé
Tos17 is a Ty1-copia retrotransposon existing in low copy number and known to be specifically activated during tissue culture in cultivated rice (Oryza sativa L.) (Hirochika et al 1996). The diversity of this element was investigated by Southern blot analyses in accessions of the Oryza genus and the related Leersia genus and a collection representative of the diversity of Oryza sativa. using a Tos17-specific reverse transcriptase probe. Tos17 was detected in all the Oryza samples but not in the African, wild species O. brachyantha and O. breviligulata, and cultivated species O. glaberrima-which was domesticated from O. breviligulata-, in the American species O. glumaepatula and in the Australian species O. meridionalis. This result suggest that either the latter species originates from ancestor representatives of the genus Oryza free of Tos17 or that the element has evolved in these species in such a way that it became not detectable by the Tos17 probe used in the study. Presence of a common hybridizing band among samples of Oryza sativa indica, which was also shared by Oryza rufipogon samples collected in the South of Himalaya in one hand, and among japonica rices on the other hand is consistent with the two independent domestications from O. rufipogon wild forms. These results open new prospects for the use of Tos17 as phylogenetic marker in rice evolution and domestication. This work was funded by the French National Genomics Initiative Génoplante. (Texte intégral)