INDUCED SYSTEMIC RESISTANCE AGAINST FUSARIUM WILT OF TOMATO BY RHIZOBACTERIAL ISOLATES

摘要

Plant growth-promoting rhizobacteria (PGPR) include bacteria in the soil rhizosphere that promote plant growth and development through a wide variety of mechanisms. In this study, potential effects of three rhizobacteria Bacillus subtilis (57-2), B. mojavensis (36-1) and B. pseudomycoides (80-1) isolated from tomato rhizosphere on induction of resistance to Fusarium oxysporum f. sp. lycopersici (Fol) were examined through biochemical and histological analyses. These PGPR isolates significantly reduced Fusarium wilt incidence up to 70%. However, the combination of isolates was found either less or not effective in suppressing the disease severity when compared to those of application by the individual isolates. The induction of peroxidase (POX, EC 1.11.1.7) and catalase (CAT, 1.11.1.6) enzymes was found to be significantly higher in treatment groups than in comparison with the control group. Present biochemical study revealed that three Bacillus spp. resulted in great accumulation of proline and key defense enzymes (POX and CAT). In situ studies also demonstrated that hydrogen peroxide (H2O2) accumulation and the callose deposition at reaction sites as a response to the pathogen attack reached to maximum level, 24 h after pathogen inoculation. The present findings revealed that PGPR isolates could be effectively used for the biocontrol of Fol through enhancing disease resistance responses of tomato plants.