Antifungal potential of essential oils, aqueous and ethanol extracts of thirteen plants against Fusarium oxysporum f . sp Lycopersici and Phytophtora infestans (Mont.) de Bary as major tomato pathogens

Abstract

Antifungal activity of essential oils (EO), ethanol extracts (ETE) and cold water extracts (CWE) of thirteen plants was evaluated against Fusarium oxysporum and Phytophtora infestans causal agents of tomato Fusarium wilt and late blight diseases respectively. The supplemented media and slide germination techniques were carried out to determine the effect of extracts on the mycelial growth and conidia germination of pathogens. The results showed that essential oils exhibited the highest antifungal activity followed by ETE and CWE. Callistemon citrinus, Cymbopogon citratus and Ocimum gratissimum essential oils were the most active inhibiting completely radial growth and conidia germination of Phytophtora infestans at 312.5 and 625 µg/ml. Essential oils of Ocimum gratissimum and Cymbopogon citratus inhibited totally the radial growth and conidia germination of Fusarium oxysporum at 625 and 312.5 µg/ml respectively. ETE of Ageratum conyzoides and Callistemon citrinus were the most active inhibiting radial growth of Phytophtora infestans. Cymbopogon citratus and Ocimum gratissimum were the most active against radial growth and conidia germination of Fusarium oxysporum at 6250 µg/ml. The fungi toxic potential of some extracts was comparable to synthetic fungicides used as positive controls. Preliminary phytochemical analysis of ETE and CWE revealed that stronger inhibiting effects were recorded with extracts rich in phenols, flavonoids, tannins, and coumarins. These findings may contribute to develop new green fungicides to protect tomato from Fusarium wilt and late blight diseases