INVESTIGATIONS OF POLLEN DISPERSAL AND OUT-CROSSING EVENTS USING TRANSGENIC GRAPEVINES: A PILOT STUDY

Abstract

Public debates about risks of genetically modified plants are often focused on putative effects of pollen dispersal and out-crossing into wild relatives or crops cultivated in the vicinity of genetically modified (GM) plants. Since first transgenic grapevines (Vitis vinifera) are being tested at various locations worldwide in the field, the question of pollen dispersal and out-crossing needs to be addressed in order to provide scientifically-based arguments. Grapevine is generally considered as a self-pollinating plant but pollen dispersal by wind and insects has to be anticipated. Thus, during 2002 to 2004, transgenic grapevines were used to quantify pollen dispersal and out-crossing events in a pilot study. As an ideal test system for monitoring experiments, transgenic ‘Dornfelder’ plants harbouring as a screenable marker the beta-glucuronidase-(GUS)-gene controlled by the 35 S RNA promoter were used. Pollen deposition could be detected up to a distance of 100 m from the pollen source. On average, the overall transgenic pollen dispersal within the evaluated radii was found to be less than 1%. The vertical gene transfer was determined by monitoring histologically GUS-activity in seedlings originating from open pollinated acceptor vines in a radial distance of 10 m and in a sector 20 m distant from the transgenic ‘Dornfelder’-pollen donor plants in the prevailing wind direction. Out-crossing events from the pollen donor plants were found to reach about 2% in the radius of 10 m and of 2.7% in the 20 m sector.