| Abstract: | Three PCR primer pairs, based on the cytokinins (etz) or IAA biosynthetic genes, were used for detecting Erwinia herbicola pv. gypsophilae in Gypsophila paniculata plants. The primers were specific to all gall-forming E. herbicola strains and distinguished them from saprophytic strains associated with gypsophila plants or from other gall-forming bacteria. In pure culture of the pathogen, less than one bacterial cell was detected with nested PCR using the etz primers - an increase of 100-fold in sensitivity as compared with single-round PCR. In the presence of plant extract a reduction of tenfold in sensitivity was observed by nested PCR. When cells were grown on a semi-selective medium prior to PCR (Bio-PCR), five cells from pure culture of the pathogen were detected. The bacteria could be detected by nested-PCR or Bio-PCR in symptomless gypsophila cuttings after 7 days. The Bio-PCR procedure described in this study can be used to establish disease-free nuclear stock of mother plants of gypsophila. |
