Antifungal Activity of Citrus Limon Leaf Extracts against Fungal Pathogens Isolated from Decaying Potato Tubers in Supermarkets of the Eastern Cape Province, South Africa

Abstract

Globally, fungal pathogens pose severe threats to stored cereal and tuber crops, resulting in substantial losses in economic crops. This study investigated the inhibitory activities of aqueous, ethanol, and acetone leaf extracts of Citrus limon L. Osbeck against the mycelial growth of Curvularia mebaldsii, Fusarium oxysporum, and Penicillium species isolated from spoilt potato tubers retailed within supermarkets in Eastern Cape Province, South Africa. Various concentrations (100 g/L, 50 g/L, and 25 g/L) of the C. limon leaf extracts (aqueous, acetone and ethanol) were prepared and (5 mL) amended with potato dextrose agar (oxoid, UK) previously inoculated with the 7-day old culture of each fungal isolates before incubation at 28 oC. The percentage growth inhibition was determined to evaluate the antifungal efficacy of each extract. Aqueous, ethanol and acetone extracts at 50g/L and 100 g/L displayed 100 % inhibition against all three pathogens except Penicillium sp. with 91.0 - 90.97 % inhibition. The ethanol and acetone extracts had the most inhibitory effects against F. oxysporum C. mebaldsii. In contrast, the aqueous extracts displayed the least effects, though not significantly different (p0.05) across the concentrations. The notable antifungal effects against F. oxysporum, a prominent pathogen of post-harvest spoilage of potatoes, suggest the potential use of C. limon extracts to enhance the shelf-life of potatoes in supermarkets, specifically, and for post-harvest storage in general.