Hydroxyl radical scavengers inhibit sclerotial differentiation and growth in Sclerotinia sclerotiorum and Rhizoctonia solani

The effect of hydroxyl radical scavengers dimethyl sulphoxide, p-nitrosodim ethylaniline, ethanol, benzoate, salicylate and thiourea was studied on scl erotial differentiation and growth of Sclerotinia sclerotiorum and Rhizocto nia solani. There is a correlation between both scavenger concentration and scavenger-hydroxyl radical reaction rate with delay and inhibition of diff erentiation at growth-noninhibiting scavenger concentrations. Growth-inhibi ting scavenger concentrations further increased delay and inhibition of dif ferentiation, and eventually stopped fungal growth, acting as antifungal an tioxidant alternatives to traditional fungicides. p-nitrosodimethylaniline (with the highest hydroxyl radical reaction rate) was the most effective in hibitor of sclerotial differentiation and growth. The results strongly supp ort the theory that oxygen free radicals induce differentiation in scleroti um-producing phytopathogenic fungi.