Fusarium infection of bread wheat and subsequent mycotoxin contamination of milling products: Impact on quality parameters and composition of flour

Abstract

Fusarium head blight (FHB) of wheat is a worldwide occurring disease reducing both grain yield and wheat quality. Grain quality is primarily degraded because of mycotoxins produced by several Fusarium spp. So far, comparatively few studies focused on the impact of FHB on technological quality traits of wheat most using rather less practical samples. With the objective to gain naturally infected samples, a field experiment was conducted in 2007-2009 at two locations with two bread wheat cultivars differing widely in their susceptibility against FHB. They were grown after pre-crop winter wheat, maize, and sugar beet using minimum tillage. Three different fungicides, strobilurin, chlorthalonil, and triazole, were applied during shooting. Whole grain flour (WGF), flour Type 550, and bran were milled from cleaned wheat and investigated for Fusarium graminearum DNA (FgDNA) and Fusarium culmorum DNA (FcDNA) as well as mycotoxin content (deoxynivalenol (DON) and derivates, zearalenone (ZEA), nivalenol and derivates). FgDNA made up the major proportion of total Fusarium DNA (FgDNA + FcDNA), DON was the most frequently detected and quantitatively most important mycotoxin in all milling products. The occurrence and quantity of FgDNA and DON was significantly influenced by all experimental factors considered, particularly year. FgDNA content was highest in bran, followed by WGF and flour Type 550. On the contrary, DON content was equally high in bran and flour Type 550 and lowest in WGF, most likely due to tempering prior milling. FgDNA and DON generally correlated strongly with visual disease as well as with/among each other. About 30 parameters assessed the properties of flour, gluten, dough, and bread as well as the composition of flour, with particular focus on gluten proteins. With means of analysis of covariance with DON as covariate and subsequent linear regression the effect of Fusarium infection on quality traits and flour composition was investigated. A significant relationship between protein content of flour Type 550, sedimentation value, falling number, dough softening, baking volume, total gluten, total glutenin, HMW-GS, gluten composition (gliadin/glutenin, LMW/HMW), protease activity, and DON was found. The direction and strength of effects is discussed as well as the practical relevance for processing. In general, a clear effect of Fusarium infection on wheat quality could only be demonstrated within few flour samples highly exceeding EU maximum levels for DON. Consequently, these flours were not relevant for further processing and human consumption. Quantitative changes in wheat quality caused by fungal infection were overall insignificant for wheat processing. Based on our observations, the impact of Fusarium infection on technological wheat quality and flour composition seems insignificant in samples that contain less DON than demanded by EU.