In vitro Antifungal Efficacy of Some Plant Extracts against Fungal Pathogens Causing Diseases in Solanaceous Crops

Abstract

Background: This research aimed to assess the antifungal potential of oil and organic leaf extracts obtained from Ocimum gratissimum, Kopsia fruticosa and Hibiscus rosa-sinensis against fungal pathogens affecting solanaceous crops. Methods: Oil of O. gratissimum was obtained by hydro-distilled method using Clevenger apparatus. Leaf extracts of K. fruticosa and H. rosa-sinensis were extracted using three organic solvents namely hexane, ethanol and methanol. The antifungal activity of the oil and organic leaf extracts against the test fungal pathogens was determined by the agar well diffusion method. The efficacy of the oil and organic leaf extracts against the pathogens was evaluated by their minimum inhibitory concentration (MIC), ability to inhibit spore germination and growth kinetic assay. Result: The oil of O. gratissimum (1000 ppm) significantly inhibited the growth of Cercospora capsici (81.4%), Alternaria alternata (73.7%) and Fusarium oxysporum (68.7%). Hexane extract of K. fruticosa and methanol extract of H. rosa-sinensis (1500 µg/well) displayed strong antifungal activity against Colletotrichum acutatum with inhibition percentages of 75.9% and 82.4% respectively. Similarly, ethanol extract of K. fruticosa and methanol extract of H. rosa-sinensis showed effective inhibition against C. capsici and A. alternata. The oil of O. gratissimum showed MIC values of 50, 100 and 200 µg/mL against C. capsici, A. alternata and F. oxysporum respectively. Ethanol extract of K. fruticosa showed MIC values ranging from 100 to 350 µg/mL, while H. rosa-sinensis methanol extract displayed MIC values ranging from 50 to 200 µg/mL against the fungal pathogens. The oil extract also demonstrated strong inhibition of spore germination of the test fungi. Our study suggests the potential of plant-derived essential oils and extracts as effective antifungal agents for crop protection.