Colorimetric method for determining hydrogen peroxide production in liquidmedia by filamentous fungi

A semiquantitative assay to estimate rates of H2O2 produced in the liquid m edium by fungi grown in a modified Georgiou-Petri dish growth apparatus in 9-cm Petri dishes is described. The method is based on the horseradish pero xidase-mediated oxidation of phenol red by H2O2 adapted to assay nmol amoun ts of H2O2 produced by fungar mycelial colonies in their own liquid media. We showed for the first time that the phytopathogen basidiomycete Sclerotiu m rolfsii produces H2O2 in the growth medium with the highest production ra te of 250 nmol/min/ g fungal dry weight at 3 d and with the highest accumul ation rate of 235 nM/min at 8 d. The assay is simple and when proper ly adj usted can provide a reasonable in vitro assessment of the capacity of vario us fungi to produce H2O2 providing a valuable tool for studying its involve ment in fungal phytopathogenicity and in microbial oxidative stress.