Inhibition of ergosterol biosynthesis by morpholine, piperidine, and spiroketalamine fungicides in Microdochium nivale: Effect on sterol composition and sterol Delta(8) -> Delta(7)-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 accu mulated 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 hy pothesis was then confirmed by sterol Delta(8) --> Delta(7)-isomerase inhib ition assays in cell-free enzyme systems. (C) 2000 Academic Press.