THE USE OF DIGOXIGENIN-LABELED PROBES TO DETECT DNA-SEQUENCES SPECIFIC FOR PLANT-PATHOGENIC BACTERIA

Southern blot hybridization is a valuable method in the assessment of the pathogenicity of bacterial strains or isolates. It is also a power ful tool for the demonstration of the presence of foreign DNA sequence s in the genome of genetically-engineered plant cells. In this respect , cold, digoxigenin-labelled DNA probes can be used in place of classi cal radioactive probes, whether hybridizations are performed on bacter ial genomic or plasmidic DNA, or on plant genomic DNA. The versatility of this cold labelling makes it suitable for the detection of unique bacterial genomic or plasmid sequences, even though these are located on large plasmids. The sensitivity of this cold probe technique also p ermits the detection of subpicogram quantities of DNA in plant genomic preparations. Their long term storage stability allows them to be fre quently re-used over long periods of time, making this technique quite cost efficient.