Fusarium head blight and trichothecene production in wheat by Fusarium graminearum and F. meridionale applied alone or in mixture at post-flowering Camila P. Nicolli 1 & Piérri Spolti 1 & Casiane S. Tibola 2 & José Maurício C. Fernandes 2 & Emerson M. Del Ponte 1,3 Received: 20 January 2015 /Accepted: 10 April 2015 /Published online: 9 May 2015 # Sociedade Brasileira de Fitopatologia 2015 Abstract A greenhouse study was conducted to expand our knowledge of the disease and mycotoxin production by Fusarium graminearum (Fgra) and F. meridionale (Fmer) in- oculated at post-flowering, either alone or in equal mixture, into three cultivars varying in their reaction to Fusarium head blight (FHB) in the field. In the first experiment, the entire spike was spray-inoculated and the proportion of diseased spikes (or inci- dence, INC) was monitored up to 15 days after inoculation (dai). In the second experiment, the inoculum was dispensed into the central-spikelet and the proportion of disease spikelets (or severity, SEV) was evaluated at 15 dai. The inoculum com- position and the inoculum x cultivar interaction on both exper- iments were not significant. However, BRS 194, a standard for susceptibility, had significantly higher INC and SEV than BRS Parrudo and BRS 179, the latter a standard for moderate resis- tance. Fmer was less damaging to grain yield than Fgra and grain yield of BRS Parrudo was the least affected among the cultivars. Trichothecenes (DON + NIV) were detected in both experiments, irrespectively of the cultivar, at levels up to 2,000 and 15,000 μg/kg, in the spray-inoculation and central-spikelet inoculation experiment, respectively. Fgra alone produced only DON and Fgra+Fmer produced mainly DON and small amount of NIV. Fmer produced mainly NIV, but also trace amounts of DON. Our results suggest that post-flowering infections may contribute with trichothecenes in mature grain, especially DON. Nevertheless, NIV should be considered in analytical surveys due to its high toxicity. Keywords Triticum aestivum . Deoxynivalenol . Nivalenol . FGSC Introduction Fusarium head blight (FHB) is a major concern to wheat pro- duction worldwide not only because of grain yield losses but also due to the presence of dangerous mycotoxins in harvested grain (McMullen et al. 2012). Deoxynivalenol (DON), a type- B trichothecene, is the most significant mycotoxin given its widespread occurrence in wheat grain at levels of concern (Del Ponte et al. 2012). Such problem has led to the establish- ment of maximum tolerance limits of DON in small grains and byproducts in North America (Miller et al. 2013), Europe (Cheli et al. 2014) and Brazil (ANVISA 2011). However, nivalenol (NIV), another trichothecene mycotoxin, has been found at equal or higher concentrations than DON in the Netherlands, Japan and Brazil (Tanaka et al. 1990 ; Thammawong et al. 2010; Del Ponte et al. 2012). Members of the Fusarium graminearum species complex (FGSC) are the main cause of FHB worldwide (O’Donnell et al. 2004; Aoki et al. 2012). FGSC isolates are known to possess three specific profiles of trichothecene production, or chemotypes (chemical phenotype), including: nivalenol (NIV) and its acetyl-derivatives, DON and primarily 3- acetyl(A)deoxynivalenol(DON), and DON and primarily 15- ADON (Miller et al. 1991). PCR-based assays targeting por- tions of genes predictive of trichothecene synthesis have been used to determine the trichothecene genotype as predictive of Section Editor: Adalberto Café * Emerson M. Del Ponte delponte@ufv.br 1 Departamento de Fitossanidade, Universidade Federal do Rio Grande do Sul, 91540-000 Porto Alegre, RS, Brasil 2 Embrapa Trigo - Empresa Brasileira de Pesquisa Agropecuária, 99001-970 Passo Fundo, RS, Brasil 3 Present address: Departamento de Fitopatologia, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brasil Trop. plant pathol. (2015) 40:134–140 DOI 10.1007/s40858-015-0017-9