Effect of benomyl on lignin degradation by some fungi

ABSTRACT

Fusarium oxysporum f. sp. vasinfectum, F.O. f.sp. Lycopersici and Aspergillus fumigatus could grow and metabolize cotton lignin when added as a sole carbon source to the culture media under control conditions [absence of fungicide]. The highest growth rate was achieved by A. fumigatus followed by F.O. f.sp. vasinfectum and F.O. f.sp. Lycopersici respectively. Conversely, the ligninolytic activity indicated that F.O. f.sp. Vasinfectum [cotton pathogen] solubilized larger quantities of phenols, as an intermediate product from degradation of cotton Iignin, followed by F.O. f.sp. lycopersici whereas A. fumigatus possessed the least ligninolytic activity. Addition of low levels of benomyl accelerated both growth and Iignin degradation by the three species, while the higher levels were inhibitory to them. The mycelial growth ceased at 1000, 800 and 200 ppm benomyl in A. fumigatus, F.O. f.sp. Vasinfectum and F.O. f.sp. Lycopersici, respectively, but Iignin degradation was detected at all fungicide concentrations. P-hydroxyberizoie, vanillic and syringic acids were spotted from the reaction mixture of the three fungi under control conditions. Vanillic acid was recorded at higher quantities and its metabolization by the three fungal species was continued at all benomyl concentrations. Addition of benomyl at low concentrations increased the solubilization of vanillic acid and significantly decreased that of p-hdyroxy benzoic and syringic acids. Higher benomyl concentrations inhibited vanillic acid production and totally arrested the formation of other phenolic acids