Study of the antifungal activity of Citrus sinensis (Rutaceae) essential oil on Ganoderma resinaceum (Ganodermataceae), a parasitic and wood-decaying fungus of mango and oil palm trees in Cameroon

Background: Ganoderma resinaceum is a parasitic fungus of oil palms and fruit trees in Africa in general and Cameroon in particular, where it often affects almost half of the plantation stands, causing destruction on several levels. Aims and Objectives: In order to solve the problems of trunk base rot commonly encountered in palm groves and fruit crop fields, which is responsible for enormous losses to human food supplies and the economy, Citrus sinensis essential oil was tested on Ganoderma resinaceum mycelium and its inhibitory and fungicidal activity was evaluated. Material and Methods: The mycelium of G. resinaceum is obtained from cultures on PDA medium with fragments of carpophores collected from the trunks of fruit trees. The essential oil of C. sinensis was extracted by hydrodistillation method using a Clevenger apparatus. This essential oil is tested on the mycelial growth of G. resinaceum by microatmosphere and direct contact method. Results: The yield of essential oil extracted from the pericarp of C. sinensis is 0.84%. This oil, slows the growth of G. resinaceum mycelium at concentrations of 0.125, 0.25 and 0.5 µL/mL and shows inhibitory activity at a concentration of 1 µL/mL and fungicidal activity at concentrations of 1, 1.25 and 2 µL/mL with respective inhibition percentages of 27. 55, 32.37, 68.83, 100, 100 and 10.59, 15.22, 69.94, 100, 100 % at different methods. C. sinensis essential oil has a significantly positive effect on the parasitic and wood-decaying fungus G. resinaceum due to its high content of more than 50% monoterpenes, which are volatile compounds with antibacterial, antiviral and antifungal properties. Conclusion: Essential oils are most often used against microscopic pathogenic fungi in food, the environment and crops, particularly Aspergillus, Fusarium, Candida, Phytophthora and Pythium. This study shows that they can also be applied in the same way as natural extracts to macroscopic parasitic fungi that cause several destructions in fruit trees such as mango and oil palm.