In vitro investigations on host specificity of Ralstonia solanacearum among solanaceous crops and its biological control in tomato

Ralstonia solanacearum, the causal organism of bacterial wilt of solanaceous crops is a major limitation on the production of solanaceous crops worldwide. The present studies were carried out to explore the prevalence, severity, virulence and host specificity range of R. solanacearum in chili, tomato, eggplant and potato plants while biocontrol of this pathogen was studied on tomato. The isolation and the initial identification of bacterium were done on TTC and 523 media. Out of 32 isolates, 30 showed positive hypersensitive reaction (HR) with variable response and were confirmed as R. solanacearum by performing biochemical tests i.e. Gram staining, KOH, catalase oxidation, Kovacs oxidation, levan production from sucrose, lipase activity on tween 80 agar, production of fluorescent pigment, and oxidation/fermentation of glucose. Race identification studies showed that all the isolates belonged to Race 3 while biovar confirmation tests revealed that 4, 3 and 23 isolates belonged to biovar 1, biovar 2 and biovar 3, respectively. The isolates belonging to distinct biovar class were tested for their wideness of host range by challenging them to chili, tomato, eggplant and potato plants. It was observed that biovar 3 is the most aggressive and has widest host range as compared to counterparts. Biocontrol studies through antagonistic rhizobacteria resulted four antagonistic isolates; PRB10, PAP5, PAT1 and PTR6 having the highest biocontrol activity with 98.75%, 97.5%, 93.75% and 91.25% respectively.