Biological management of Sclerotinia rot of bean through enhanced host defense responses triggered by Pseudomonas and Trichoderma species

Abstract

Plant growth promoting microorganisms have been reported to induce systemic resistance in plants. In the present study, a consortium comprising of Trichoderma harzianum and Pseudomonas aeruginosa were evaluated for their efficacy to control Sclerotinia rot of bean. Upon infection of bean plants with the S. scIerotiorum resulted in substantial changes in enzymatic and non-enzymatic defense related compounds. The induction of phenylalanine ammonia-lyase (PAL), peroxidase (POx), polyphenoloxidase (PPO), superoxide dismutase (SOD), and the accumulation of proline and phenols in bean leaves were studied periodically at 2 d intervals after pathogen infection. Levels of PAL and phenols were induced most rapidly and increased significantly in all the treatments after pathogen challenge and reached maximum after 2 d and 4 d of pathogen challenge, respectively. Similarly, the activities of POx, PPO, SOD, along with proline content was also found to increase consistently and reached maximum at 6 d after pathogen challenge and their content was maximum in plants treated with microbial consortium. These results demonstrated that interaction of microorganism in rhizosphere could provide enhanced tolerance against pathogen through induction of host defenserelated compounds.