ROLE OF Pseudomonas fluorescens IN INDUCED SYSTEMIC RESISTANCE FOR TOMATO VASCULAR WILT DISEASE CAUSED BY Fusarium oxysporum F. SP. LYCOPERSICI

Abstract

Using an isolate of Pseudomonas fluorescens (Pf) in biological control was found to protect tomato plants from vascular wilt disease caused by Fusarium oxysporum f. sp. lycopersici (Fol). In spite of the In vitro partially inhibition effect of Pf on mycelial growth of Fol by 47%, it found that Pf treatment one week before inoculation can decrease the diseases severity in tomato plants by 87%. These results indicating that systemic protection offered to tomato roots by the Pf for vascular wilt disease caused by Pol infection and explaining that ISR is involved. Induction of defense enzymes by Pf against challenge inoculation with Fol in tomato was studied. Activities of phenylalanine ammonia-lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO) increased in bacterized tomato root tissues challenged with the pathogen. Analysis revealed that a PAL, POX and PPO were expressed at higher levels in bacterized tomato root tissues challenge inoculated with the pathogen. Activities of PAL and POX reached maximum at the 4th day while, activity of PPO reached maximum at the 6th day after challenge inoculation. Induction of these enzymes activities was found, not only in Pf treated root tissues challenged with the pathogen, but also in roots treated with Pf alone. These results suggest that induction of defense enzymes involved in phenylpropanoid pathway might have contributed to restriction of invasion of Fol in tomato plants.