Isolated rhizobacteria of Jatropha curcas L.: antagonistic activity of phytopathogens and plant growth promoter

Introduction: Jatropha curcas L. is a species native to Mexico that has recently been considered an important crop to produce biofuel. Objective: To isolate and identify rhizobacteria from J. curcas with antagonistic activity against phytopathogenic fungi (Curvularia lunata and Fusarium equiseti) of this crop and evaluate their capacity to promote tomato plant growth. Materials and methods: The isolates were obtained by serial dilution and antagonistic activity was assessed by volatile and diffusible compounds on PDA medium. In addition, the production of antifungal compounds and metabolites that promote the plant growth were determined. The isolates were identified by amplifying the 16S RNA and sodA genes. Finally, the isolates were inoculated on tomato seeds to evaluated plant growth promotion and germination. Results and discussion: The antagonistic bacteria were identified as Bacillus mojavensis, Bacillus subtilis, Bacillus thuringiensis, and Pseudomonas aeruginosa. The antifungal effect on the mycelial growth of C. lunata and F. equiseti was due to the presence of volatile and diffusible compounds with between 30 % and 79 % inhibition. Pseudomonas aeruginosa showed the strongest inhibitory effect (48.7 to 79.8 %). Bacillus subtilis (A1), B. mojavensis (A4) and B. thuringiensis (A6, A8) showed the highest germination (70 % to 88 %). The vegetative growth of tomato plants treated with the isolates was significantly higher than the controls (P < 0.05). Conclusion: Eight rhizobacteria isolated from J. curcas showed antagonistic activity against C. lunata and F. equiseti and demonstrated their capacity to improve the germination and promote growth in tomato plants.