Biocontrol of post-harvest Alternaria alternata decay of cherry tomatoes with rhamnolipids and possible mechanisms of action.

BACKGROUND: Rhamnolipids were reported to have evident antifungal activity. The efficacy of rhamnolipids against Alternaria alternata and their possible mechanisms involved were investigated. RESULT: The decay incidences of A. alternata of cherry tomatoes (Lycopersicon esculentum) treated by rhamnolipids were significantly reduced. The in vitro assays showed that rhamnolipids inhibited fungal growth on solid medium and prevented spore germination and mycelium growth in liquid medium. In addition, the combination of rhamnolipids and essential oil had a synergistic effect leading to the decrease of fungicidal concentrations of laurel oil. Scanning electron microscopy and transmission electron microscopy observations of the pathogen revealed significant morphological and cell structural alterations in the hyphae. Compared to the control, the content of nucleic acid in supernatant of the suspension of A. alternata increased, while the content of DNA and protein of mycelium decreased, which was in agreement with electrolyte leakage experiments.
CONCLUSION: Rhamnolipids could be an alternative to chemicals for controlling post-harvest phytopathogenic fungi on fruits and vegetables.