Detection and Identification of Bacterial Speck of Tomato (Pseudomonas syringae pv. tomato) by Polymerase Chain Reaction

Fifty bacterial isolates of Pseudomonas syringae pv. tomato (Okabe) the causal agent of bacterial speck of tomato, were isolated and identified from diseased tomato samples collected from different tomato growing areas in Jordan. The 650 bp coronatine genes cluster was detected in all Ps. syringae pv. tomato tested isolates by using Two 17- bp oligonucleotide primers; primer 1 and primer 2 by PCR analysis. To detect variation among the tested isolates of Pseudomonas syringae pv. tomato, the 650 bp PCR products of the six different isolates present in six different locations were digested with five restriction enzymes namely; PstI, ClaI, SmaI, CfoI and HaeIII. Fragments of identical sizes were obtained from these isolates, which prove that this gene cluster is highly conserved. Moreover, the Pseudomonas syringae pv. tomato was found to be translocated systemically throughout the infected tomato shoots, since this pathogen was detected by direct isolation on KB medium followed by pathogenicity test and by PCR analysis from the sap of symptomless tomato plant shoots. Furthermore, for the detection of systemic infection, the results indicated that the detection of bacterial speck of tomato, using PCR amplification of coronatine gene is highly efficient and more rapid than direct isolation on KB medium followed by pathogenicity test