Effects of triazoles on fungi: IV. Growth and lipids of Cercospora arachidicola and Cercosporidium personatum

The effects of propiconazole (a sterol C-14 demethylation inhibitor) on the growth and lipid content of Cercospora arachidicola and Cercosporidium personatum were examined in vitro using gravimetric, chromatographic, and colorimetric techniques. The lipid content and composition of both species were very similar. C_16:0, C_18:1, and C_18:2 were the principal fatty acids of the major acyl lipids, ergosterol (ergosta-5,7,22-trienol) was the principal sterol, and free fatty acids comprised a large portion (ca. 30%) of lipid. Cercospora and Cercosporidium were both very sensitive to the inhibitor; 0.10 to 0.15 μg propiconzole/ml was required for an average of approximately 50% growth inhibition among isolates on a mycelial dry weight basis. Changes in lipid composition were similar in both species grown in media containing the inhibitor. The total sterol content was twofold higher than that in the corresponding controls, which was due to the accumulation of ergosterol precursors (e.g., 24-methylene dihydrolanosterol). The free fatty acid content of treated mycelia was lower than that of the controls, and the degree of unsaturation of the lipids was higher, particularly in phosphatidylcholine. Also, the ratio of saturated to unsaturated fatty acids was less in the polar lipid of inhibitor-treated mycelium than in controls.