Isolation and Characterization of an Antagonistic Endophytic Bacterium Bacillus velezensis CB3 the Control of Citrus Green Mold Pathogen Penicillium digitatum

In order to develop environment friendly fungicide for the control of citrus green mold (Penicillium digitatum) using endophytic bacteria, the 21 bacterial isolates were isolated from citrus leaves in seven different orchards in Jeju Province. Among the 21 bacterial isolates, 5 bacterial isolates presented antifungal activity against green mold pathogen P. digitatum. The CB3 isolate, which showed the most strong antagonistic effect, was selected through opposite culture against the pathogen. The rod-shaped, gram-positive bacterium CB3 was identified as Bacillus velezensis based on morphological, physiological characteristics, 16S rDNA, and gyr A gene sequence analysis. The isolate CB3 showed strong antifungal activity against two citrus postharvest pathogen P. digitatum. Citrus fruits were treated by wound inoculation with P. digitatum pathogen, and the control efficacy of CB3 culture broth was 66.7% (1×10∨8 cfu/ml). In conclusion, The stability of CB3 and its strong antifungal activity also lead us to believe that it has potential for application as an environment friendly biological control agent.