EFFECT OF DINICONAZOLE ON STEROL COMPOSITION OF ROOTS AND CELL-SUSPENSION CULTURES OF FENUGREEK

Diniconazole, a triazole-type fungicide had no plant growth regulating activity on fenugreek seedlings but decreased the growth of fenugreek cell suspensions by about 20%. Exposure of the fenugreek seedlings or cells to diniconazole caused inhibition of sterol biosynthesis at the 14 alpha-demethylation step leading to accumulation of 14 alpha-methy l-Delta(8)-sterols concomitant with a decrease in the sitosterol and s tigmasterol content. 14 alpha-Methyl-Delta(8)-sterols represented 67.8 % of total sterols in treated cell suspensions and 28% in treated root s compared with 0.5 and 0.4%, respectively, in untreated tissues. An a ccumulation of 14 alpha-methyl Delta(8)-sterols with a C-8-side chain (92% of the 14 alpha-methyl Delta(8)-sterols) such as 14 alpha-methyl- 5 alpha-cholest-8-en-3 beta-ol and 4 alpha,14 alpha-dimethyl-5 alpha-c holest-8-en-3 beta-ol was found in treated roots. In contrast, in fenu greek cell suspensions, 52.8% of the accumulated 14 alpha-methyl Delta (8)-sterols had a C-9-side chain, such as in 14 alpha-methyl-5 alpha-e rgosta-8,24(24(1))-dien-3 beta-ol, 14 alpha-methyl-5 alpha-ergost-8-en -3 beta-ol and 4 alpha,l4 alpha-dimethyl-5 alpha-ergosta-8,24(24(1))-d ien-3 beta-ol, and 43.8% had a C-10-side chain, such as in 14 alpha-me thyl-5 alpha-stigmasta-8,24(24(1))-dien-3 beta-ol and 4 alpha,14 alpha -dimethyl-5 alpha-stigmasta-8,24(24(1))-dien-3 beta-ol. Results point to the early reduction-methylation bifurcation at the Delta(24) double bond of sterol precursors which are converted with few interconnectin g routes To the end-product sterols, i.e. cholesterol or phytosterols.