Bioprospecting of rhizobacteria with antagonistic activity against Fusarium spp., a parasite of cucumber (Cucumis sativus)

Objective: To identify bacteria of genus Bacillus which, isolated from the tomato and cucumber rhizosphere, have an antagonistic effect against Fusarium spp. isolated from cucumber plants in Culiacan, Sinaloa. Design/Methodology/Approach: Both the in vitro and in vivo antagonisms of rhizobacterial isolates against Fusarium spp. on cucumber plants were evaluated. Bacteria with the highest antagonistic effect were identified based on their morphological and molecular characteristics. Results: Isolates FA15 and FA16 showed the highest in vitro biological efficacy against Fusarium spp., with 50.0% and 61.36% inhibition of mycelial growth, respectively. Rhizobacterium FA15 achieved the highest biological efficacy (88.89%) against Fusarium spp. in cucumber plants, while rhizobacterium FA16 recorded a 59.27% efficacy. The morphological and molecular characterization of isolates FA15 and FA16 confirmed a 100% molecular identity between FA15 and Bacillus velezensis and FA16 and B. subtilis. Study Limitations/Implications: The rhizobacteria identified in this study inhibited the mycelial growth of the phytoparasite. Therefore, further studies about these rhizobacteria should be carried out to determine the potential antibiosis that may cause the inhibitory effect. Findings/Conclusions: During the search for native beneficial rhizobacteria, two bacteria that exercise a biologically-effective control over Fusarium spp were identified in Culiacan: Bacillus velezensis and B. subtilis. This finding offers an opportunity in the agricultural biotechnology field to study beneficial native species that could provide an alternative to the use of chemicals.