Effect of Epiphytic Bacteria from Citrus against Green Mold Post-Harvest Diseases of Citrus

Abstract

This study investigates the potential of epiphytic bacteria isolated from citrus fruits to control green mold post-harvest disease caused by Penicillium digitatum in Thompson Navel sweet oranges in the north of Iran. Twenty-three epiphytic bacteria were isolated and screened in vitro against P. digitatum, and 13 isolates with antagonistic activity were selected for further studies. Isolates B15 (Bacillus sp.), P17 (Pseudomonas sp.), and S13 (Streptomyces sp.) exhibited the most effective inhibitory effects on P. digitatum in vitro and in vivo. Among these, B15 showed the highest percentage of mycelium growth reduction and was further identified as B. cereus by 16S rRNA sequence analysis. Metabolic analysis of Bacillus sp. isolate B15 extract revealed the presence of the inhibiting antifungal substance Iturin A. The result showed that the application of epiphytic B. cereus decreased the percentage of green mold post-harvest diseases in orange fruit. This indicates their potential as an environmentally friendly alternative to chemical post-harvest control of orange diseases caused by P. digitatum.