Effect of tridemorph and fenpropimorph on sterol composition in fenugreek

The addition of tridemorph (125 mu M) during growth of fenugreek seedlings or the addition of fenpropimorph (125 mu M) in the culture medium of fenugreek cell suspensions resulted in a large accumulation of 9 beta,19-cyclopropyl sterols (about 50% of total sterols) concomitant with a decrease in the Delta(5)-sterol content (40-50% of total sterols compared with more than 90% in control cultures). However the 9 beta,19-cyclopropyl sterols accumulated differed depending on the tissue studied-fenugreek roots or cells. In roots of seedlings treated with tridemorph, pollinastanol and 4 alpha,14 alpha-dimethyl-9 beta,19-cyclo-5 alpha-cholestan-3 beta-ol were the major cyclopropyl sterols while in treated-cell suspensions with fenpropimorph, 24-methylenepollinastanol and 24-methylpollinastanol were the major sterols. These results indicated that these compounds inhibited the cycloeucalenol-obtusifoliol-isomerase (COI). Moreover, in roots as well as in cell suspensions, these inhibitors led to a weak accumulation of Delta(8)-sterols indicating that Delta(8) --> Delta 7 isomerase was also affected. Finally, we observed that only fenpropimorph induced an accumulation of Delta(8,14)-sterols in cell suspensions, showing that Delta(14)-reductase can also be inhibited by this fungicide.