In this study an LC-MS/MS multitoxin method covering a total of 247 fungal and bacterial metabolites was applied to the analysis of different foods and feedstuffs from Burkina Faso and Mozambique. Overall, 63 metabolites were determined in 122 samples of mainly maize and groundnuts and a few samples of sorghum, millet, rice, wheat, soy, dried fruits, other processed foods and animal feeds. Aflatoxin B(1) was observed more frequently in maize (Burkina Faso, 50% incidence, median = 23.6 μg/kg; Mozambique, 46% incidence, median = 69.9 μg/kg) than in groundnuts (Burkina Faso, 22% incidence, median = 10.5 μg/kg; Mozambique, 14% incidence, median = 3.4 μg/kg). Fumonisin B(1) concentrations in maize were higher in Mozambique (92% incidence, median = 869 μg/kg) than in Burkina Faso (81% incidence, median = 269 μg/kg). In addition, ochratoxin A, zearalenone, deoxynivalenol, nivalenol, and other less reported mycotoxins such as citrinin, alternariol, cyclopiazonic acid, sterigmatocystin, moniliformin, beauvericin, and enniatins were detected. Up to 28 toxic fungal metabolites were quantitated in a single sample, emphasizing the great variety of mycotoxin coexposure. Most mycotoxins have not been reported before in either country.

Fusariumgraminearum and related species commonly infest grains causing the devastating plant disease Fusarium head blight (FHB) and the formation of trichothecene mycotoxins. The most relevant toxin is deoxynivalenol (DON), which acts as a virulence factor of the pathogen. FHB is difficult to control and resistance to this disease is a polygenic trait, mainly mediated by the quantitative trait loci (QTL) Fhb1 and Qfhs.ifa-5A. In this study we established a targeted GC–MS based metabolomics workflow comprising a standardized experimental setup for growth, treatment and sampling of wheat ears and subsequent GC–MS analysis followed by data processing and evaluation of QC measures using tailored statistical and bioinformatics tools. This workflow was applied to wheat samples of six genotypes with varying levels of Fusarium resistance, treated with either DON or water, and harvested 0, 12, 24, 48 and 96 h after treatment. The results suggest that the primary carbohydrate metabolism and transport, the citric acid cycle and the primary nitrogen metabolism of wheat are clearly affected by DON treatment. Most importantly significantly elevated levels of amino acids and derived amines were observed. In particular, the concentrations of the three aromatic amino acids phenylalanine, tyrosine, and tryptophan increased. No clear QTL specific difference in the response could be observed except a generally faster increase in shikimate pathway intermediates in genotypes containing Fhb1. The overall workflow proved to be feasible and facilitated to obtain a more comprehensive picture on the effect of DON on the central metabolism of wheat.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-014-0731-1) contains supplementary material, which is available to authorized users.

Volatile organic compounds (VOCs) play a crucial role in the communication of plants with other organisms and are possible mediators of plant defence against phytopathogens. Although the role of non-volatile secondary metabolites has been largely characterised in resistant genotypes, the contribution of VOCs to grapevine defence mechanisms against downy mildew (caused by Plasmopara viticola) has not yet been investigated. In this study, more than 50 VOCs from grapevine leaves were annotated/identified by headspace-solid-phase microextraction gas chromatography-mass spectrometry analysis. Following P. viticola inoculation, the abundance of most of these VOCs was higher in resistant (BC4, Kober 5BB, SO4 and Solaris) than in susceptible (Pinot noir) genotypes. The post-inoculation mechanism included the accumulation of 2-ethylfuran, 2-phenylethanol, β-caryophyllene, β-cyclocitral, β-selinene and trans-2-pentenal, which all demonstrated inhibitory activities against downy mildew infections in water suspensions. Moreover, the development of downy mildew symptoms was reduced on leaf disks of susceptible grapevines exposed to air treated with 2-ethylfuran, 2-phenylethanol, β-cyclocitral or trans-2-pentenal, indicating the efficacy of these VOCs against P. viticola in receiver plant tissues. Our data suggest that VOCs contribute to the defence mechanisms of resistant grapevines and that they may inhibit the development of downy mildew symptoms on both emitting and receiving tissues.

Norwegian grain samples (73 oats, 75 barley, 83 wheat) from the 2000-02 growing seasons were examined for contamination with moniliformin, and the association between the fungal metabolite and the number of kernels infected with common Fusaria was investigated. Before quantification of moniliformin using ion pairing reversed-phase high-performance liquid chromatography with diode array ultraviolet light detection, all samples were extracted using acetonitrile/water (84/16) and disposable strong anion exchange columns used for clean up. The limit of detection was 40 microg kg(-1). Moniliformin was found in 25, 32 and 76% of the barley, oats and wheat samples, respectively. The maximum concentrations of moniliformin in barley, oats and wheat were 380, 210 and 950 microg kg(-1), respectively. At the same time, the prevalence and infection level of the moniliformin-producing F. avenaceum/arthrosporioides was as high as 100 and >53% on average, respectively. Moniliformin concentrations were significantly correlated to the variables grain species, growing season and infection with F. avenaceum/arthrosporioides and F. culmorum. The survey indicates that the prevalence of moniliformin in Norwegian grain is high, especially in wheat. On the other hand, field conditions in Norway do not seem to favour contamination of grain with high levels of moniliformin.

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