Field release of a genetically modified Pseudomonas fluorescens on wheat : establishment, survival and dissemination

The establishment, survival and dissemination of a strain of Pseudomonas fluorescens, that was originally isolated from the phylloplane of sugar beet and genetically modified with the marker genes lacZY and kanr-xylE was studied during a field release experiment on wheat. The genetically modified microorganism (GMM) was released into the environment onto the seed and as a foliar spray applied at tillering. Survival as well as dissemination of the GMM was greater in the field than could be predicted from experiments that were carried out in microcosm and pot experiments under contained conditions and in comparison with previous release studies with similar GMMs. The GMM used in our field release survived and multiplied especially well in the rhizosphere and phylloplane of wheat, and was found to disseminate up to 2 m away from the inoculated areas and to depths likely to be greater than the deepest sampling of 45 cm. GMM numbers in soil declined steadily over time, but numbers increased subsequently on volunteer wheat, weeds and resown wheat plants.