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EC-sponsored Research on Safety of Genetically Modified Organisms - A Review of Results
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 button Foreword
 button Research areas
imageimageimage Plants
imageimageimage Plant  microbes
imageimageimage Biocontrol
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image Assessment of risk of transfer of bacterial phytopathogenicity genes to epiphytic microbes

Background and objectives

Future strategies for the control of bacterial diseases affecting crops are likely to depend on biological control. This will involve the deliberate release of antagonistic bacteria related to the bacteria causing the disease. As certain pathogenicity genes are conserved among diverse pathogens, we need to assess the potential risk that natural gene transfer from pathogens could create harmful organisms. Appropriate containment procedures for use in the field will also have to be devised.

Approach and methodology

The general aim was to develop concepts and strategies for bacterial phytosafety based on knowledge of the structure, function, regulation and modification of genes that mediate plant-pathogen interactions. In particular, we sought to investigate the relatedness of hrp genes (which are essential for pathogenicity) among diverse pathogens; the structure, organisation and regulation of these genes; and their ability to function in non-pathogenic host bacteria.

Main findings and outcome

The hrp genes of Pseudomonas solanacearum cover a region of about 20 kb which contains nine transcriptional units. Expression of these genes is stimulated by plant extracts. The sequence of about 11 kb of this region has been completed, and reveals that the genes are related to those in P. syringae. Xanthomonas campestris hrp genes have also been cloned and mutants of these genes have properties similar to the Pseudomonas mutants; however, production of known biochemical determinants of pathogenicity is not reduced. The hrp genes from P. syringae can only be expressed in this strain and closely related phytopathogenic strains: they were not expressed in related saprophytes. It appears that the risk of new phytopathogens arising by accident is small, and should be controllable.


The project has shown that bacteria causing very different plant diseases carry similar pathogenicity genes. One class of these genes, the hrp genes, has now been extensively characterised in three different pathogens.

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Contract number

January 1989 – December 1990



M.J. Daniels
The Sainsbury Laboratory
Norwich (UK)

C.A. Boucher
Castanet-Tolosan (FR)

N. Panopoulos
Foundation for Research & Technology – Hellas
Heraklion (GR)

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