Similarities between the systemic fungicides triforine and triarimol

Abstract

The fungicides triforine and triarimol, though structurally unrelated have a similar antifungal spectrum. Neither fungicide inhibited germination of conidia of Cladosporium cucumerinum, but both inhibited subsequent mycelial growth. Triforine, like triarimol, proved to be an effective inhibitor of ergosterol biosynthesis. Two mutants of C. cucumerinum selected for resistance to triarimol also exhibited resistance to triforine and to the triarimol analogues ancymidol and bis(4-chlorophenyl)-3-pyrimidinemethanol. Resistance of these mutants, however, did not extend to the sterol inhibitors triparanol and trans-clomiphene or to sodium o-phenylphenate and 2,6-dichloro-4-nitroaniline, two compounds usually tolerated by fungi exhibiting general hydrocarbon resistance. Toxicity of either triforine or triarimol to C. cucumerinum was annuled by /I-carotene, vitamin A, progesterone, testosterone and farnesol. The various similarities between triforine and triarimol suggest a common mode of action for the two compounds. I19

Novel Fungitoxicity Assays for Inhibition of Germination-Associated Adhesion of Botrytis cinerea and Puccinia recondita Spores

“…The lack of inhibition of B. cinerea spore germination and adhesion by carbendazim and pyrimethanil shows that these fungicides affect processes that are not essential for germination. Similarly, the lack of inhibition of P. recondita spore adhesion by myclobutanil and fenbuconazole, which are highly active against wheat leaf rust (11,16), is consistent with the fact that such inhibitors of ergosterol biosynthesis typically act after germination (4,20).…”

“…On the other hand, many fungicides have little or no effect on spore germination but strongly inhibit mycelial growth. Examples of fungicides that typically act after germination in filamentous fungi include antimicrotubule agents, e.g., carbendazim and N-phenylcarbamates, which inhibit nuclear division (22), and inhibitors of ergosterol biosynthesis (4,20). Consequently, comparison of the potency of a compound as an inhibitor of germination with its activity in a mycelial growth assay can provide preliminary information on its mode of action.…”

Mode of Action of the Azasteroid Antibiotic 15-Aza-24-Methylene- d -Homocholesta-8,14-Dien-3β-ol in Ustilago maydis

“…A triarimoltolerant mutant of C. cucumerinum (19) was also tolerant to the azasterol (Table 1). When treated with azasterol, the mutant strain exhibited a narrow dosage response with a distinct cut-off point for colony development, and no tendency for colony appearance at higher concentrations with prolonged incubation.…”

Antifungal activity of eugenol against Botrytis cinerea

“…This suggests that eugenol interferes with processes taking place after the stages of germination. Many fungicides such as carbendazim and Nphenylarbmates have little or no effect on spore germination but strongly inhibit mycelial growth (Sherald et al, 1973;Suzuki et al, 1984). Nevertheless, the reason why eugenol was not effective in reducing conidia germination of B. cinerea needs to be further investigated.…”