Elicitation of plant defense enzymes against Fusarium oxysporum f. sp. lycopersici in tomato plant using a novel rhizobacteria Providencia rettgeri MSS2

Providencia rettgeri MSS2, a novel gamma proteobacterium, isolated from the rhizospheric soil of tomato plant in Gujarat, India has in vitro biocontrol activity against Fusarium oxysporum f. sp. lycopersici (FOL), causative agent of fusarium wilt in tomato plant. It also has a strong root colonization potential which was confirmed by SEM analysis. Talc-based bioformulation of MSS2 was applied under pot trials to study the mechanism of induced resistance against FOL by enhancement of defense enzymes and total phenolics in tomato. Results of the study showed an increase in the defense enzymes like peroxidase (PO) and polyphenoloxidase (PPO), maximum increase of these enzymes was observed on the 6th day of pathogen challenge. Enzyme activity was found to be increased by 1.2 fold in the plants pretreated with MSS2 and challenged with FOL as compared to only pathogen treated plants. Activity of phenylalanine ammonium lyase (PAL) was also found to increase in plants pretreated with MSS2 challenge inoculated by FOL. Increase in total phenolics upto 1.7 fold was found in the plants treated with MSS2 challenge inoculated by FOL than untreated plants. Zymographic study for both defense enzymes showed induction of isoform PO2, PPO1 and PPO4 in the rhizobacterial treated plant challenged with pathogen than with untreated and pathogen control plants. Plant root colonizing ability of the rhizobacteria P. rettgeri MSS2 helps in the significant induction of enhanced plant defense response against phytopathogen FOL.