Alternative methods to control postharvest disease of mango

Abstract

Anthracnose, a fungal disease caused by the Colletotrichum gloeosporioides, and mango fruit flies (Bactrocera zonata) are the two main postharvest problems regarding the production of mangoes (Mangifera indica L.) on the islands of Reunion and Madagascar. Traditional postharvest treatments can negatively affect mango quality so that it does not comply with customers' and export countries expectations. Physical treatments are generally used against fruit flies, as well as chemical products against C. gloeosporioides. Our goal was to develop alternative methods for postharvest treatment, using the fungitoxic properties of various essentials oils and controlled atmospheres (hypoxia). For a start, these treatments were applied in vitro, to C. gloeosporioides conidia, appressoria and mycelium in PDA culture, and to eggs of Bactrocera zonata. The fungitoxic effects of Ravensara aromatica and clove (Eugenia aromatica) essential oils were measured on spores, germination, and on the mycelium growth. Essential oil of E. aromatica inhibited the pathogen growth in vitro and blocked conidial germination. The effect of the hypoxic treatment was measured in vitro on hatching of B. zonata eggs. Four days of treatment were necessary to kill all eggs. The second step was to measure the effects these treatments had on the fruit physiology. Various polyphenols in mango peel were synthesized after both treatments. Hypoxic conditions and essential oils' effects on fruit quality were also key data. Biochemical parameters of fruit quality such as pH, acidity and sugars were measured to verify whether these treatments meet customer's expectations.