Boris Bekaert

The compositional mosaic of Fusarium species and their mycotoxins in unprocessed cereals, food and feed products in Belgium

Global food safety depends on continuous monitoring of food contaminants such as mycotoxins in cereals and cereal-derived products. Here, we combine this type of investigation with quantitative occurrence data on Fusarium infestation of these products in extensive correlation studies. Finally, this contributes to a thorough understanding of the presence, origin and physiology of Fusarium Head Blight (FHB) related mycotoxins and the correlations within their ranks. Two hundred and thirty-seven samples were analyzed from diverse cereal matrices, representing the most important stages of the cereal food and feed chain in Belgium. Food, feed and non-processed field samples were investigated, with a strong emphasis on whole-grain food products. Two approaches were pursued to estimate the full scope of FHB and its repercussions: UPLC-MS/MS was applied to detect twelve different mycotoxins, and Q-PCR was used to measure the presence of ten Fusarium species. We found that different matrices have different characteristic contamination profiles, and extensive correlation studies identified certain mycotoxins for future assessment (e.g. moniliformin produced by the Fusarium avenaceum/Fusarium tricinctum species group). The investigated harvest year of 2012 yielded many non-processed field materials containing elevated levels of deoxynivalenol (DON), while even in a so-called DON-year less prevalent toxins such as T-2 and HT-2 might be considered problematic due to their consistent co-occurrence with related mycotoxins. Our data illustrate complex interactions between the many Fusarium species that are responsible for FHB and their mycotoxins. Correlation studies demonstrate that consistent co-occurrence of mycotoxins is not to be neglected, and pinpoint issues for future surveillance and legislation.

Detached leaf in vitro model for masked mycotoxin biosynthesis and subsequent analysis of unknown conjugates

The manuscript details the development of an in vitro model plant system using detached leaves because there is a need for biosynthetic methods for the production and isolation of masked mycotoxins. This detached leaf in vitro model was firstly applied to deoxynivalenol with satisfying results. The biosynthesis of deoxynivalenol-3-glucoside was confirmed using its respective commercially available reference standard. Secondly, the detached leaf in vitro model was applied to T-2 toxin. Mono- and tri-glucoside derivatives of T-2 toxin and HT-2 toxin, T-2-(3)-glucoside, T-2-(3)-triglucoside and HT-2-(3)-glucoside were identified and characterised using Orbitrap high-resolution mass spectrometry. This is the first report on a triglucoside of T-2 toxin. The discovery of new masked forms implies the importance of the development of analytical methods for their detection, the constitution of toxicity studies, and proving the relevance of their presence in the food and feed chain.

Control of Fusarium verticillioides (Sacc.) Nirenberg and fumonisins by using a combination of crop protection products and fertilization

Fusarium verticillioides is the most common fungal pathogen associated with maize ear rot in Tanzania. In a two-year trial, we investigated the efficacy of crop protection (insecticide and/or fungicide) and fertilizer (nitrogen and/or phosphorus) treatments in reducing the occurrence of F. verticillioides and its mycotoxins in maize grown in Tanzania. Seasonal differences were seen to have a substantial influence on the incidence and severity of insect infestation, Fusarium ear and kernel rot, biomass of F. verticillioides and contamination with fumonisins. With regard to the application of fertilizers, it was concluded that the impact on maize stalk borer injury, Fusarium symptoms and fumonisin levels was not significant, whereas crop protection significantly reduced maize damage. The application of an insecticide was most effective in reducing insect injury and as a result of the reduced insect injury the insecticide treatment also resulted in a significant decrease in Fusarium symptoms. In 2014, fumonisin levels were also significantly lower in maize treated with an insecticide. Additionally, significant positive correlations between insect damage and Fusarium symptoms were observed. In conclusion, this study clearly shows that application of an insecticide alone or in combination with a fungicide at anthesis significantly reduces insect damage and consequently reduces F. verticillioides infection and associated fumonisin contamination.

Genetic divergence and chemotype diversity in the fusarium head blight pathogen Fusarium poae

Fusarium head blight is a disease caused by a complex of Fusarium species. F. poae is omnipresent throughout Europe in spite of its low virulence. In this study, we assessed a geographically diverse collection of F. poae isolates for its genetic diversity using AFLP (Amplified Fragment Length Polymorphism). Furthermore, studying the mating type locus and chromosomal insertions, we identified hallmarks of both sexual recombination and clonal spread of successful genotypes in the population. Despite the large genetic variation found, all F. poae isolates possess the nivalenol chemotype based on Tri7 sequence analysis. Nevertheless, Tri gene clusters showed two layers of genetic variability. Firstly, the Tri1 locus was highly variable with mostly synonymous mutations and mutations in introns pointing to a strong purifying selection pressure. Secondly, in a subset of isolates, the main trichothecene gene cluster was invaded by a transposable element between Tri5 and Tri6. To investigate the impact of these variations on the phenotypic chemotype, mycotoxin production was assessed on artificial medium. Complex blends of type A and type B trichothecenes were produced but neither genetic variability in the Tri genes nor variability in the genome or geography accounted for the divergence in trichothecene production. In view of its complex chemotype, it will be of utmost interest to uncover the role of trichothecenes in virulence, spread and survival of F. poae.

Early sowing and harvesting as effective measures to reduce stalk borer injury, Fusarium verticillioides incidence and associated fumonisin production in maize

Maize cultivation in Tanzania is hampered by the presence of maize stalk borer (Busseola fusca) and Fusarium verticillioides, causing ear, kernel and stalk damage. Furthermore, accumulation of fumonisin mycotoxins deteriorates grain quality. Optimized agronomic practices remain the primary line of defense against pests and diseases. Therefore, the aim of this study was to gain insight into the effects of hybrid, sowing and harvest date on injuries due to maize stalk borer, Fusarium verticillioides symptoms and fumonisin contamination in maize grown in Tanzania. The analyses of the data collected during two growing seasons (2013 and 2014) showed early sowing and early harvesting as important measures for minimizing these problems. Although the impact of hybrid was not always significant, the early maturing hybrid STUKA M1 was consistently less susceptible compared to the hybrid STAHA. Correlation analysis revealed that stalk borer injuries, Fusarium symptoms and fumonisin levels were positively associated. The associations between yield and stalk borer injuries, Fusarium symptoms and fumonisin levels were negative, indicating that besides the mycotoxin issues, the insect and fungal pathogen also contribute to yield losses.