Molecular identification of the causal agent of bacterial wilt in tomato plants in southwestern Parana

Bacterial wilt, caused by phytopathogenic species of the genus Ralstonia, is one of the main diseases affecting the tomato crop. The Ralstonia solanacearum species complex occurs as a result of variants being widely diverse in terms of adaptation to different climatic conditions, host variations, and aggressiveness, which complicate disease control recommendations. In this study, we employed molecular methods to analyze 26 R. solanacearum isolates collected from tomato plants cultivated in the southwest region of Parana, Brazil. Isolates were obtained from plants exhibiting wilt symptoms in a protected cultivation system and in an open field. The specific primers 759/760 confirmed the isolates as part of the Ralstonia solanacearum complex, and Nmult primers were used to identify the phylotype. Variability analysis using BOX-PCR with the BOX-A1R primer on 19 isolates revealed molecular diversity. All 26 isolates were confirmed as Ralstonia solanacearum, belonging to phylotype II. Comparison of genomic DNA band patterns amplified by BOX-PCR indicated molecular variability, forming eight groups at a similarity level of 0.63. These results confirm the prevalence of R. solanacearum phylotype II in southwestern Parana. This information aids decision-making in disease management and contributes to breeding efforts aiming at the development of resistant cultivars.