Postharvest treatment of mango: Potential use of essential oil with thymol to control anthracnose development

Introduction - Anthracnose, a fungal disease caused by the Colletotrichum gloeosporioides species is the main postharvest problem concerning mango (Mangifera indica) production on La Reunion Island. Traditional postharvest treatments involve chemical compounds that do not comply with the expectations of consumers or importing countries. Chemical treatments are generally used against C. gloeosporioides. Our goal was to develop alternative postharvest treatments using the fungitoxic properties of two essential oils (EO). Materials and methods - Two commercial essential oils, X2 and X5, were used at various concentrations and compared to a no-oil control. A first batch of treatments were tested in vitro for studying mycelial growth and the inhibition of conidial germination. The second experiment measured the effects of the treatments on the fruit quality of inoculated mangoes var. Tommy Atkins with a solution of C. gloeosporioides spores. Results and discussion - In vitro, X5 mainly composed of thymol was very fungitoxic against C. gloeosporioides. The concentrations of phenolic compounds and resorcinol in the fruits were increased after the X5 treatments, expressing some positive effects of essential oil treatments on fruit resistance mechanisms. The quality of treated fruits verified the requirements to meet consumers' expectations. Conclusion - Thymol-based EO exhibited a strong fungitoxic in vitro activity but it had no detectable effect when applied by volatilization on mango necrosis. Alternatives ways of treatments should be tested.