Plant Growth Regulating Properties of Sterol-Inhibiting Fungicides

Abstract

A group of sterol-inhibiting fungicides, diverse with respect to chemical structure but with the same specific mode of action, has been recently introduced for plant disease control (Siegel, 1981). They belong to the chemical class of triazoles, imidazoles, pyrmidines, morpholines, piperazines, and the structures of some of the compounds are illustrated in Figure 6.1 (Kato, 1982). Most of the compounds are highly active in controlling various economically important fungal diseases including, powdery mildew, smut, bunt, and rust fungi. In other words they control a wide range of diseases caused by Ascomycetes, Basidomycetes and Deuteromycetes and they are not used to control Phycomycetes. The sterol-inhibiting fungicides block ergosterol biosynthesis by inhibiting C-14 demethylation reactions. The specific mechanisms of inhibition of ergosterol biosynthesis which eventually curtails membrane synthesis and fungal growth are discussed by Siegel (1981) and Kato (1982). The mode of action of these fungicides as inhibitors of lipid biosynthesis, in particular the sterol component and the effects of other plant growth retardants suggesting possible sites of inhibition are covered in an excellent review by Ragsdale (1977).