Repression of deoxynivalenol accumulation and expression ofTrigenes inFusarium culmorumby fungicidesin vitro

Abstract

A defined medium was developed in which to monitor deoxynivalenol (DON) accumulation, fungal growth and expression of genes involved in trichothecene biosynthesis (designated Tri genes). In liquid culture, DON accumulated shortly after maximum expression of Tri6 and coincident with expression of Tri5. This was generally 96 h after inoculation. The effects of sublethal concentrations of the fungicides azoxystrobin, trifloxystrobin, kresoxim-methyl and tebuconazole on biosynthesis of the trichothecene DON by Fusarium culmorum were studied using this medium. The strobilurin fungicides trifloxystrobin and azoxystrobin significantly reduced the accumulation of DON in culture medium at a range of concentrations. Kresoxim-methyl, also a strobilurin, and tebuconazole, a triazole, did not significantly reduce the accumulation of DON, although levels were lower than those in nonamended cultures. Trifloxystrobin significantly reduced the accumulation of DON when added to cultures before initiation of trichothecene biosynthesis. RT-PCR assays of the expression of Tri6 and Tri5 genes indicated that trifloxystrobin acted by inhibiting the initiation of trichothecene biosynthesis.

Nutrient profiling reveals potent inducers of trichothecene biosynthesis in Fusarium graminearum

“…The identification of nitrate as a repressor of TRI5 induction is also strongly suggestive of a direct role for the global nitrogen regulatory system, common to many ascomycetous fungi (reviewed in Marzluf, 1997), in DON biosynthesis. Other authors have also noted that nitrate does not support DON production in F. culmorum (Covarelli et al, 2004). Nitrate in the media used for carbon source screening here could be responsible for the lack of induction observed by any carbon source.…”

The pH regulatory factor Pac1 regulates Tri gene expression and trichothecene production in Fusarium graminearum

“…Most of these studies show an influence of environmental or extra-cellular factors on toxin production but only few have elucidated a molecular regulation of Tri genes expression by highlighting the role of Tri6 and Tri10. Among the factors modulating trichothecenes regulation, a profound effect has been demonstrated in liquid cultures for treatments with hydrogen peroxide (Ponts et al, 2007) or fungicides (Covarelli et al, 2004), temperature (Shmidt-heydth et al, 2008), carbon and nitrogen sources (Miller and Greenhalgh, 1985;Jiao et al, 2008) magnesium (Pinson-Gadais et al, 2008) and phenolic acids (Boutigny et al, 2009). A variety of amines were also identified as potent inducers of DON production (Gardiner et al, 2009a).…”

Neutralized electrolyzed water efficiently reduces Fusarium spp. in vitro and on wheat kernels but can trigger deoxynivalenol (DON) biosynthesis

“…during anthesis, can pose a serious impediment for an efficient Fusarium targeted control in the field. In addition, several lines of evidence illustrate elevated DON biosynthesis when fungicides are applied sub optimally (Audenaert, Callewaert, Hofte, De Saeger, & Haesaert, 2010;Covarelli, Turner, & Nicholson, 2004) Although Fusarium is a typical field pathogen which is essentially controlled in the growing crop, it is hard to completely abrogate the fungus from crude wheat kernels and both fungus and concomitant mycotoxins remain a serious issue during storage and processing of wheat derived products. Therefore, several postharvest measures are available to control mycotoxins and fungi.…”