Antifungal effects of two tropical plant leaf extracts (Ocimum gratissimum and Aframomum melegueta) on postharvest yam (Dioscorea spp.) rot

Effects of leaf extracts of Ocimum gratissimum and Aframomum melegueta on spore germination and mycelial reduction of the most occurring fungal pathogen causing soft rot of yam tuber were investigated. Fungi isolated from rotted yams were Aspergillus niger, A. flavus, Fusarium oxsporium Rhizopus stolonifer, Botryodiplodia theobromae and Penicillium chrysogenum. The leaf extracts with ethanol extraction were most effective followed by cold-water and hot water extraction. The fungicidal activity with Ocimum gratissimum leaf extracts was more effective. In vitro inoculation of fresh yam with A. niger, A. flavus and F. oxsporum at room temperature for 3 months showed typical rot symptoms characteristic of the disease. The significance of these findings is discussed in relation to plant chemical or non-chemical means of disease control on yams in Africa.