Evaluation of a DNA probe for the detection of Erwinia herbicola strains pathogenic on Gypsophila paniculata

A 7.5-kb DNA fragment carrying genes for indole acetic acid biosynthesis in Erwinia herbicola pv. gypsophilae was used as a DNA probe to detect gall-forming E. herbicola strains. A quick colony hybridization procedure was developed to detect E. herbicola pv. gypsophilae in cuttings of gypsophila, and was compared with ELISA and pathogenicity tests. The sensitivity of the colony hybridization procedure was sufficient to detect less than 100 colony-forming units after enrichment culture. In mixed cultures, with saprophytes associated with the gypsophila plant, about 104 CFU/ml of the pathogen were detectable. The colony hybridization is specific to gall-forming E. herbicola strains, and is relatively easy to perform. The advantages of using the colony hybridization procedure for practical purposes, compared with ELISA and pathogenicity tests, are discussed.