Control of Fusarium Dry Rot Incited by Fusarium oxysporum f. sp. tuberosi Using Sargassum vulgare Aqueous and Organic Extracts

Aqueous and organic extracts of Sargassum vulgare, removed from four Tunisian coastal sites, were evaluated for their antifungal potential against the soilborne fungus Fusarium oxysporum f. sp.tuberosi, one of the main causal agents of potato Fusarium dry rot in Tunisia.Assessed using the poisoned food technique on Potato Dextrose Agar, the antifungal activity of S. vulgare extracts varied depending on extract types (aqueous/organic), alga sampling sites (Tunis, Monastir, Mahdia1 and Mahdia2) and concentrations used (1-100 mg/ml).Mycelial growth inhibition, noted after 4 days of incubation at 25°C, reached 28.99% using S. vulgare aqueous extract at 100 mg/mL.Up to 43% growth inhibition was achieved using 50-100 mg/ml of petroleum ether extract of S. vulgare removed from Tunis and Mahdia2, and up to 50% with those from Mahdia1. S. vulgare aqueous and organic extracts decreased Fusarium dry rot severity, noted after 21 days of incubation at 25°C, in a concentration dependant manner.Applied prior to pathogen challenge, treatment with aqueous extract (at 100 mg/mL) led to 24 and 30% decrease in lesion diameter and rot penetration over the untreated control.Tubers treated with aqueous extracts of alga sampled from Tunis showed the lowest dry rot severity compared to those from the other sampling sites.Chloroformic and methanolic extracts exhibited the highest disease-suppressive effects relative to untreated control and to the other organic extracts.Applied at 100 mg/mL, the methanolic and chloroformic extracts have lowered disease severity by more than 53 and 55%, respectively.This study clearly demonstrated that this brown alga can be valorized as a potential source of antifungal compounds useful in agriculture.