Isolate-specific resistance of 71 cultivars and breeding lines of wheat (Triticum aestivum) to septoria tritici blotch was evaluated in six field trials in the Netherlands, Switzerland and the UK between 1995 and 1997. Each plot was inoculated with one of six single-pycnidium isolates of the pathogen Mycosphaerella graminicola. There were strong interactions between wheat lines and M. graminicola and the line-by-isolate interactions were stable over the six trials. Lines with specific resistance or specific susceptibility to each of the isolates were identified. Specific resistance to isolate IPO323 was especially common, being carried by 22 lines from 10 countries. The results confirm that lineby-isolate interactions in septoria tritici blotch of wheat are effective in adult plants in field conditions, and are not simply confined to seedlings. Wheat lines with good, quantitative resistance to all or most isolates were identified, including lines from Brazil, the USA and seven European countries. These may be useful as sources of resistance in wheat breeding.

Deoxynivalenol and zearalenone are among the most prevalent toxins produced by Fusarium spp. They have been investigated in food and feed products for decades but rarely in the environment. We therefore established solid-phase extraction and liquid chromatography-mass spectrometry (LC-MS) methods to quantify these mycotoxins at trace concentrations in aqueous natural samples. In a model emission study, we inoculated a winter wheat field with Fusarium graminearum and subsequently monitored deoxynivalenol and zearalenone in its drainage water. Before during and after harvest in June and July 2007, these toxins were emitted in concentrations from 23 ng/L to 4.9 µg/L for deoxynivalenol and from not detected to 35 ng/L for zearalenone. Simultaneously, in July and August 2007, deoxynivalenol was also detected in a number of Swiss rivers in concentrations up to 22 ng/L and zearalenone was present in several river samples below the method quantification limit. Other mycotoxins might be emitted from Fusarium-infected fields as well, because some of them are produced in similar amounts as deoxynivalenol and zearalenone and exhibit similar or even higher water solubility than deoxynivalenol. The ecotoxicological consequences of the presence of mycotoxins in surface waters remain to be elucidated.

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The mycotoxin zearalenone (ZON) is a very potent natural endocrine disrupting chemical, produced by Fusarium graminearum fungi growing on crops such as wheat and maize. Although it is well-investigated in food and feed, very little is known about its environmental fate and behavior. Here, we report the occurrence of ZON on F. graminearum infected wheat and maize fields in crop organs and soil and its emission via drainage water. ZON amounts in the investigated crops and topsoil were between 6.1 and 25.0 and up to 5.6 g/ha, respectively. ZON concentrations in drainage water were in the low nanogram per liter range with a maximum of 35 ng/ L. Cumulated ZON amounts emitted via drainage water ranged from 0.1 to 4.3 mg/ha, depending on the crop cultivated in the respective period. This corresponds to fractions between 0.001 and 0.070% of the initially present ZON amount in the plants. Because of the low concentrations emitted via drainage water, it can be assumed that ZON contributes little if at all to the overall estrogenicity of major surface water bodies. However, in small creeks, mainly fed by agricultural runoff, ZON might be present in environmentally critical concentrations at times of F. graminearum infections.

Maize is frequently infected by the Fusarium species producing mycotoxins. Numerous investigations have focused on grain maize, but little is known about the Fusarium species in the entire plant used for silage. Furthermore, mycotoxins persist during the ensiling process and thus endanger feed safety. In the current study, we analyzed 20 Swiss silage maize samples from growers’ fields for the incidence of Fusarium species and mycotoxins. The species spectrum was analyzed morphologically and mycotoxins were measured by LC-MS/MS. A pre-harvest visual disease rating showed few disease symptoms. In contrast, the infection rate of two-thirds of the harvest samples ranged from 25 to 75% and twelve different Fusarium species were isolated. The prevailing species were F. sporotrichioides, F. verticillioides and F. graminearum. No infection specificity for certain plant parts was observed. The trichothecene deoxynivalenol (DON) was found in each sample (ranging from 780 to 2990 µg kg−1). Other toxins detected in descending order were zearalenone, further trichothecenes (nivalenol, HT-2 and T-2 toxin, acetylated DON) and fumonisins. A generalized linear regression model containing the three cropping factors harvest date, pre-precrop and seed treatment was established, to explain DON contamination of silage maize. Based on these findings, we suggest a European-wide survey on silage maize.

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The Fusarium species complex of maize kernels and stem pieces as well as mycotoxin contamination of commercial grain maize hybrids for animal feed were evaluated in Switzerland. Throughout 2 years, natural Fusarium infection varied significantly between the years and the locations and it ranged from 0.4% to 49.7% for kernels and from 24.2% to 83.8% for stem pieces. Using the agar plate method, 16 different Fusarium species were isolated from kernels and 15 from stem pieces. The Fusarium species composition, prevalence and impact differed between the north and the south and between kernel and stem piece samples.