Phytochemical screening and control of fungal diseases of cocoa (Theobromae cacao L.) pod using extracts of plant origin

The antifungal activity of the ethanolic leaf extracts of Dioscorea dumetorum and Moringa oleifera on the fungal pathogens isolated from infected cocoa pods were investigated in vitro and in vivo. The pathogens were Botryodiplodia theobromae and Fusarium moniliformes. For the in vitro assay, 5ml of various concentrations of the extracts ranging from 10g/200ml, 20g/200ml, 30g/200ml, 40g/200ml and 50g/200ml were separately added to PDA media. The fungal pathogens were separately inoculated into the media and incubated for seven days. For the in vivo, healthy cocoa pods were properly surfaced sterilized using 99% ethanol and Sodium hypoclorite (bleach). The sterile cocoa pods were then sprayed with the extracts at different concentrations two hours prior to inoculation with the fungal pathogens. Each cocoa pod after being treated with different concentration of the extracts at 10g/200ml, 20g/200ml, 30g/200ml, 40g/200ml and 50g/200ml were dipped into beakers containing dissolved spores of each pathogen and incubated for twenty eight days. Results of the in vitro studies showed that at 10g/200ml, 20g/200ml, 30g/200ml, 40g/200ml and 50g/200ml concentrations, ethanolic leaf extract of D. dumetorum and M. oleifera completely inhibited the radial growth of B. theobromae and F. moniliformes after seven days observation period while results of the in vivo studies showed that the extracts had a significant effect (p ≤ 0.05) on the mycelial growth of the fungal pathogens at all the concentrations tested. Phytochemical screening of the plant extracts showed that cardiac glycosides, anthraquinones, and reducing compounds were highly present in D. dumetorum and M. oleifera extracts while saponnins and phlobatannins were absent.