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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 14α-demethylation step leading to accumulation of 14α-methyl δ 8 -sterols concomitant with a decrease in the sitosterol and stigmasterol content. 14 α -Methyl- δ 8 -sterols represented 67.8% of total sterols in treated cell suspensions and 28% in treated roots compared with 0.5 and 0.4%, respectively, in untreated tissues. An accumulation of 14α-methyl Δ 8 -sterols with a C 8 -side chain (92% of the 14α-methyl Δ 8 -sterols) such as 14α-methyl-5α-cholest-8-en-3β-ol and 4α-dimethyl-5α-cholest-8-en-3β-ol was found in treated roots. In contrast, in fenugreek cell suspensions, 52.8% of the accumulated 14α-methyl Δ 8 -sterols had a C 9 -side chain, such as in 14α-methyl-5α-ergosta-8,24(24 1 )-dien-3β-ol, 14α-methyl-5α-ergost-8-en-3β-ol and 4α,14α-dimethyl-5α-ergosta-8,24(24 1 )-dien-3β-ol, and 43.8% had a C 10 -side chain, such as in 14α-methyl-5α-stigmasta-8,24(24 1 )-dien-3β-ol and 4α,14α-dimethyl-5α-stigmasta-8,24(24 1 )-dien-3β-ol. Results point to the early reduction-methylation bifurcation at the Δ 24 double bond of sterol precursors which are converted with few interconnecting routes to the end-product sterols, i.e. cholesterol or phytosterols. |
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