GENE FLOW BETWEEN CULTIVATED AND WILD SUNFLOWERS

With the development of transgenic crops, concern has been expressed r egarding the possible escape of genetically-engineered genes via hybri dization with wild relatives. This is a potential hazard for sunflower s because wild sunflowers occur as weeds in fields where cultivated su nflowers are grown and hybridization between them has been reported. I n order to quantify the potential for gene escape, two experimental st ands of sunflower cultivars were planted at two sites with different r ainfall and altitude profiles. Populations of wild plants were planted at different distances from each cultivar stand. An allele homozygous in the cultivar (6Pgd-3-a), but absent in the wild populations, was u sed as a molecular marker to document the incidence and rate of gene e scape from the cultivar into the wild populations of sunflowers. Three -thousand achenes were surveyed to determine the amount of gene flow f rom the cultivated to the wild populations. The marginal wild populati ons (3 m from the cultivar) showed the highest percentage (27%) of gen e flow. Gene flow was found to decrease with distance; however, gene f low occurred up to distances of 1000 m from the source population. The se data suggest that physical distance alone will be unlikely to preve nt gene flow between cultivated and wild populations of sunflowers.