Résumé
The objective of this study was to assess the frequency of pollen-mediated gene flow from a transgenic rice line, harbouring the gusA gene and the bar gene encoding respectively â-glucuronidase and phosphinothricin acetyl transferase as markers, to the red rice weed and conventional rice in the Spanish japonica cultivars Senia. A circular field trial design was set up to investigate the influence of the wind on the frequency of pollination of red rice and conventional rice recipient plants with the transgenic pollen. Frequencies of gene flow based on detection of herbicide resistant, GUS positive seedlings among seed progenies of recipient plants and averaged over all the wind directions were 0.036 ± 0.006% and 0.086 ± 0.007 for red rice and conventional rice respectively. However, for both red rice and conventional rice, a clear asymmetric distribution was observed with pollination frequency favoured in plants placed under the local dominant winds. The hemizygous status and the origin of the transgenes was confirmed by analysing the progenies of surviving, GUS positive plants. Examination of the influence on gene flow frequency of the distance from the transgenic source to recipient plots of conventional rice planted at 1, 2, 5 and 10 m distance revealed a clear decrease with increasing distance which was less dramatic under the dominant wind direction. The precise determination of the local wind conditions at flowering period and pollination day time appear of primary importance for setting up suitable isolation distances. (Texte intégral)