Anthracnose disease is compromising citrus production in the Mediterranean area including Tunisia. Aromatic plants are a source of bioactive compounds with antimicrobial applications. Thus, this study aims to identify and characterize the growth and aggressiveness of fungal strains isolated from the most cultivated Citrus species in the Cap Bon region in Tunisia, as well as the antifungal properties of eleven essential oils against this disease. Twenty fungal strains were isolated from leaves and fruit of five citrus species showing anthracnose spots were identified as Colletotrichum gloeosporioides based on ITS and CAL gene sequences. The strains exhibited different colony morphologies and growth kinetic in culture on SNA and PDA media, with abundant conidia production on SNA medium. The pathogenicity tests on lemon leaves and fruit showed different degrees of aggressiveness depending on the strain and plant organ, with no significant correlation between the aggressiveness of the fungal strains on leaves and fruit. Thyme essential oil showed the lowest minimal concentration that reduce C. gloeosporioides growth by 50%. The bioprotection tests on lemon leaves and fruit showed 50% of reduction in fungal infection using the MIC50 concentration of thyme essential oil, and over 90% of infection reduction using double the MIC50 concentration without any visible phytotoxicity on both plant parts. These results suggest that thyme essential oil is a potential biofungicide for pre- and post-harvest control of Citrus anthracnose disease.
Aouini et al. (Sun,) studied this question.