Demethylation inhibitors

Sensitivities (ED50) of 200 monoconidial isolates of Venturia inaequalis to the sterol demethylation inhibitor flusilazole (38) were determined, based on the inhibitory effect on mycelial growth [96]. 

In summary, prochloraz, like other azoles, is an ergosterol biosynthesis inhibitor (i.e. it is an EB1) and it does this by blocking 14-demethylation (such compounds are sometimes referred to as demethylation inhibitors, or DMIs). As is now well known, these molecules bind to the sterol binding site of the demethylase enzyme in such a way as to allow the azole to bind to an iron atom in the active site (see below). The normal physiological reaction is therefore prevented. 

Imazalil treatments (1-2 g/L in water/wax sprays) applied in commercial packinghouses failed to control decay or sporulation of the resistant biotypes. Six imazalil-resistant isolates were cross-resistant in vitro to 8 other sterol demethylation inhibitors, But were sensitive to tridemorph and fenpropimorph. 

Monilinia. a limited number of treatments is recommended in mixtures and alternations with conventional products and demethylation inhibitors. 

Demethylation-Inhibitor Resistance Research and Management Goals and Their Implementation in North America... 

Since research on the growth and biochemical responses, as well as resistance, to sterol inhibitors has been recently reviewed (8-14) this information will be covered here only insofar as necessary to establish the background for a discussion on the molecular basis for fungal growth inhibition by these substances. Since most of the work has been conducted with C-14 demethylation inhibitors, emphasis will be given to them, particularly the azoles. 

Figure 3. Diagrams portraying the interaction of 14a-methyl sterol (A) and a sterol C-14 demethylation inhibitor (B) with cytochrome in the region of the heme prosthetic group.

G1 3 C14-DeMethylation Inhibitors in sterol biosynthesis (DMI fungicides) Piperazines, pyridines, pyrimidines, imidazoles, triazoles Prochloraz, propiconazole, tebuconazole, epoxiconazole, prothioconazole Broad spectrum over 30 commercial compotmds... 

Sterol Biosynthesis Inhibitors (SBIs) and Demethylation Inhibitors (DMIs)... 

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