Inhibition of Ergosterol Biosynthesis by Morpholine, Piperidine, and Spiroketalamine Fungicides in Microdochium nivale: Effect on Sterol Composition and Sterol Δ8 → Δ7-Isomerase Activity

Microdochium nivale, a wheat pathogenic filamentous fungus, appeared to be very sensitive in in vivo laboratory assays to fenpropimorph and tridemorph and to a lesser extent to fenpropidin, piperalin, and spiroxamine. It accumulated Delta(8)-sterols when grown in the presence of one of these sterol biosynthesis inhibitors. Thus, in M. nivale, these fungicides seemed to be Very good inhibitors of the sterol Delta(8) --> Delta(7)-isomerase. This hypothesis was then confirmed by sterol Delta(8) --> Delta(7)-isomerase inhibition assays in cell-free enzyme systems. (C) 2000 Academic Press.