Abstract
Tridemorph, at a concentration of 10μM, hardly inhibited spore germination of Botrytis cinerea but caused multiple emergence of the germ tubes and their excessive branching, inhibiting hyphal extension. The morphological abnormality was similar to that caused by buthiobate. In addition, tridemorph at the above concentration inhibited ergosterol biosynthesis in B. cinerea as strongly as buthiobate. However, the site of inhibition during the sterol biosynthetic pathway was distinct from that of buthiobate. The analysis of sterols in the control and treated cultures indicated that tridemorph possibly blocked the Δ8→Δ7 isomerization, i. e. the conversion of fecosterol to episterol, but buthiobate inhibited the demethylation at the C-14 position of sterol nucleus. A higher concentration (100μM) of tridemorph inhibited spore germination of B. cinerea, caused a prominent leakage of the cellular constituents, and suppressed the incorporations of glucose-U-14C, leucine-U-14C and uracil-U-14C. But, such effects were not detected at lower fungitoxic concentrations (10 and 30μM). Thus, a high antifungal activity of tridemorph at low concentrations can be possibly attributed to the inhibition of ergosterol biosynthesis.
