HIGHLY SPECIFIC PCR-DIAGNOSIS TO DETERMINE PSEUDOMONAS-SOLANACEARUM STRAINS OF DIFFERENT GEOGRAPHICAL ORIGINS

Using a PCR-based assay with highly specific primers, we were able to clearly identify all of 28 different Pseudomonas solanacearum strains, whereas none of the other bacteria tested gave a cross reaction. The PCR sensitivity in standard dilution experiments of pure strains was i n the range of 10 to 100 cells. The assay was also investigated for it s suitability in routine diagnosis of potato tubers and tomato plants inoculated with various amounts of P. solanacearum; it reached a sensi tivity of 10(3) cells per specimen. The region between primers PS96H a nd PS96I was sequenced for the first time and aligned. A total of 17 P . solanacearum strains have been sequenced, resulting in six different sequence groups. When the variable sequence was analyzed, a high corr elation between point mutations and geographical origin of the P. sola nacearum strains was revealed. The PCR assay described in this study c ombined with automatical sequencing of the amplificated region provide s a powerful tool for the epidemiology of P. solanacearum.