Sterol-Inhibiting Fungicides: Effects on Sterol Biosynthesis and Sites of Action. Malcolm R. Siegel, Department of Plant Pathology, University of Kentucky, Lexington 40546. Plant Dis. 65:986-989. Accepted for publication 17 March 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-986.

A group of fungicides, diverse with respect to chemical structure, spectrum of biological activity, and degree of systemicity, has recently been introduced for plant disease control. Fungal mutants selected for resistance to one member of this group of fungicides usually display resistance to other members as well. This phenomenon of cross-resistance indicates a common mode of action. Biochemical analysis of the toxic action of these compounds in fungal cells revealed that ergosterol biosynthesis is rapidly inhibited. This inhibition eventually curtails membrane synthesis and fungal growth. The details of the toxic action, effects on sterol biosynthesis, and sites of action of the sterol-inhibiting fungicides are discussed.