The biological control agent Pseudomonasfluorescens was used against the bacterial wilt causing Ralstoniasolanacearum. The present investigation focuses on the role of defenserelated enzymes in imparting resistance in tomato against R. solanacearum. A total of ten rhizobacterial isolates werescreened against R. solanacearum, ofwhich three isolates (Pf3, Pf5 & Pf8) showed a maximum inhibition againstthe pathogen and were further identified as P.fluorescens by 16S rRNA analysis. Seedling treatment with P. fluorescens isolates significantlyenhanced the quality of seed germination and seedling vigor. The three P. fluorescens strains were furthertested for their ability to induce the production of defense-related enzymes inplants. Involvement of defense related enzymes in bacterial wilt pathogenesiswas studied in susceptible tomato cultivar (Arka Meghali). Root dip inoculationwas performed with bacterial suspensions of R.solanacearum and P. fluorescens (1× 108 cfu/ml) on ten days old seedlings and harvested at differenttime intervals (0, 3, 6, 9, 12, 15, etc. up to 72 h) and assayed for thedefense related enzyme activity. The seedling treatment of P. fluorescens isolatesinduced a significant increase in the activities of peroxidase (POX), Polyphenoloxidase (PPO), phenylalanine ammonia lyase (PAL), and β-1, 3-glucanase in treated tomato plants and the same trend ofincrease in enzyme activity was observed in P.fluorescens treated tomato seedlings challenged with R. solanacearum. The activities of the enzymes PAL, POX, PPO and β-1, 3-glucanase reached maximum at 24,18, 24 and 24 h after inoculation respectively. Higher accumulation ofphenolics was noticed in plants pre-treated with P. fluorescens and challenge inoculated with R. solanacearum. Native PAGE analysis of both Peroxidase (POX) andPolyphenol oxidase (PPO) was carried out for the time course of enzymeactivities and the isoforms of POX and PPO were examined
