Resistance to Sterol Demethylation Inhibitors in Ustilago maydis. III. Cross‐Resistance Patterns and Sterol Analyses

Abstract

Two spontaneous triadimefon-resistant mutants of Ustilago maydis, 151ar/l and 151ar/3, were investigated with regard to their extent of crossresistance and their sterol composition to elicit indications about the specificity of the present resistance mechanisms. Testing resistance to various sterol biosynthesis inhibitors and toxicants with different modes of action, it could be demonstrated that, in the mutant 151ar/l, cross-resistance was limited to the sterol demethylation inhibitors (DMIs), whereas, in strain 151ar/3, resistance included most sterol biosynthesis inhibitors studied (DMIs, morpholines, piperidines, allylamines) as well as the unrelated compounds vinclozolin and cycloheximide. Sterol analyses showed that both mutants contained ergosterol as the main sterol component. In comparison with the sensitive reference strain, the mutant 151ar/l had a slightly elevated content of C-14 methyl sterols, whereas in strain 151ar/3 the amount of ergosterol was increased. Triadimefon caused an accumulation of C-14 methyl sterols and a decrease in ergosterol content in the sensitive strain and the mutant 151ar/l, whereas the other strain 151ar/3 remained unaffected. The results indicate that several resistance mechanisms are probably operating in the two mutants.

Sensitivities to DMI fungicides in populations of Podosphaera fusca in south central Spain

“…4b), indicating a cross‐resistance consistent with the great similarity of the two molecules, as previously suggested 26. Cross‐resistance to DMIs has been reported in many fungal pathogens 13, 37–40. In P. fusca , isolates resistant to triadimefon have been detected with a higher tolerance to myclobutanil and propiconazole 12.…”

The adaptation of Fusarium culmorum to DMI Fungicides Is Mediated by Major Transcriptome Modifications in Response to Azole Fungicide, Including the Overexpression of a PDR Transporter (FcABC1)

“…Davis) and Zymoseptoria tritici ([Desm.] Quaedvlieg & Crous) (Wellmann et al, 1996 ; Hsiang et al, 1997 ; Robbertse et al, 2001 ; Cools and Fraaije, 2012 ). The adapted strain even seemed to be a little less affected by a curative tebuconazole treatment applied on infected wheat ears compared with the wild-type strain, although this difference was not statistically supported.…”

Genetic control of the resistance of Erysiphe graminis f.sp. hordei to five triazole fungicides

“…Resistances to different triazoles have been found to be associated in diverse fungi, including Venturia inaequaliz (Stanis & Jones, 1985; Thind et al ., 1986; Hildebrand et al ., 1988; Köller et al ., 1997; Kunz et al ., 1997), Guignardia bidwellii (Thind et al ., 1986), Nectria haematococca var. cucurbitae (Kalamarakis et al ., 1989), Rhynchosporium secalis (Kendall & Hollomon, 1990; Kendall et al ., 1993), Ustilago maydis (Wellmann et al ., 1996), Uncinula necator (Erickson & Wilcox, 1997), Mycosphaerella graminicola (Gisi et al ., 1997) and Cladosporium caryigenum (Reynolds et al ., 1997). Some of these studies also detected correlations between resistances to triazoles and to other classes of DMI (imidazoles, pyrimidines and piperazines), while others did not.…”