RESUMO
AIMS: In the study, seven Plant Growth Promoting Rhizobacteria (PGPR) Azotobacter species were screened against three strains of Fusarium verticillioides to test its antifungal activity. Azotobacter strains were tested for the degradation of fumonisin produced by F. verticillioides. Secondary metabolites were isolated and characterized from the Azotobacter strains for the first time. METHODS AND RESULTS: Potential seven Azotobacter species antifungal activity was tested following the dual culture assay against three strains of Fusarium verticillioides namely FVM-42, FVM-86 and MTCC156 estimating the substantial zone of inhibition. Azotobacter species AZT-31 and AZT-50 strains significantly inhibited the growth of F. verticillioides recording drastic growth enhancement of maize under in-vitro conditions by calculating the infection incidence, vigour index and germination percentage. As confirmation, dereplication studies were conducted for the reconfirmation of Azotobacter strains by isolating from rhizoplane. Azotobacter strains played a key role in the degradation of fumonisin produced by F. verticillioides reporting 98% degradation at 2 h of incubation with the pathogen. Furthermore, in the study first time, we have tried to isolate and characterize the secondary metabolites from the Azotobacter strains exhibiting six compounds from the species AZT-31 (2) and AZT-50 (4). Preliminary in-vitro experiments were carried out using the compounds extracted to check the reduction of infection incidence (90%) and increase in germination percentage upto 50 to 70% when compared to the test pathogen. CONCLUSION: Azotobacter strains referred as PGPR on influencing the growth of plant by producing certain substances that act as stimulators on inhibiting the growth of the pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: The future perspective would be the production of an active combination of carboxamide compound and Azotobacter species for preventively controlling the phytopathogenic fungi of plants and crops and also towards the treatment of seeds.
