IN VITRO INVESTIGATIONS ON HOST SPECIFICITY OF RALSTONIA SOLANACEARUM AMONG SOLANACEOUS CROPS AND ITS BIOLOGICAL CONTROL IN TOMATO

摘要

Ralstonia solanacearum, the causal organism of bacterial wilt of solanaceous crops is a major limitation on theproduction 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 thispathogen 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, levanproduction from sucrose, lipase activity on tween 80 agar, production of fluorescent pigment, and oxidation/fermentation ofglucose. Race identification studies showed that all the isolates belonged to Race 3 while biovar confirmation tests revealedthat 4, 3 and 23 isolates belonged to biovar 1, biovar 2 and biovar 3, respectively. The isolates belonging to distinct biovarclass were tested for their wideness of host range by challenging them to chili, tomato, eggplant and potato plants. It wasobserved that biovar 3 is the most aggressive and has widest host range as compared to counterparts. Biocontrol studiesthrough antagonistic rhizobacteria resulted four antagonistic isolates; PRB10, PAP5, PAT1 and PTR6 having the highestbiocontrol activity with 98.75%, 97.5%, 93.75% and 91.25% respectively.