EFFECT OF TRIDEMORPH AND FENPROPIMORPH ON STEROL COMPOSITION IN FENUGREEK

The addition of tridemorph (125 mu M) during growth of fenugreek seedl ings or the addition of fenpropimorph (125 mu M) in the culture medium of fenugreek cell suspensions resulted in a large accumulation of 9 b eta,19-cyclopropyl sterols (about 50% of total sterols) concomitant wi th 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,1 9-cyclopropyl sterols accumulated differed depending on the tissue stu died-fenugreek roots or cells. In roots of seedlings treated with trid emorph, 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 indi cated that these compounds inhibited the cycloeucalenol-obtusifoliol-i somerase (COI). Moreover, in roots as well as in cell suspensions, the se inhibitors led to a weak accumulation of Delta(8)-sterols indicatin g that Delta(8) --> Delta 7 isomerase was also affected. Finally, we o bserved that only fenpropimorph induced an accumulation of Delta(8,14) -sterols in cell suspensions, showing that Delta(14)-reductase can als o be inhibited by this fungicide.