Influence of agronomic and climatic factors on Fusarium infestation and mycotoxin contamination of cereals in Norway.

A total of 602 samples of organically and conventionally grown barley, oats and wheat was collected at grain harvest during 2002-2004 in Norway. Organic and conventional samples were comparable pairs regarding cereal species, growing site and harvest time, and were analysed for Fusarium mould and mycotoxins. Agronomic and climatic factors explained 10-30% of the variation in Fusarium species and mycotoxins. Significantly lower Fusarium infestation and concentrations of important mycotoxins were found in the organic cereals. The mycotoxins deoxynivalenol (DON) and HT-2 toxin (HT-2) constitute the main risk for human and animal health in Norwegian cereals. The impacts of various agronomic and climatic factors on DON and HT-2 as well as on their main producers F. graminearum and F. langsethiae and on total Fusarium were tested by multivariate statistics. Crop rotation with non-cereals was found to reduce all investigated characteristics significantly--mycotoxin concentrations as well as various Fusarium infestations. No use of mineral fertilisers and herbicides was also found to decrease F. graminearum, whereas lodged fields increased the occurrence of this species. No use of herbicides was also found to decrease F. langsethiae, but for this species the occurrence was lower in lodged fields. Total Fusarium infestation was decreased with no use of fungicides or mineral fertilisers, and with crop rotation, as well as by using herbicides and increased by lodged fields. Clay and to some extent silty soils seemed to reduce F. graminearum in comparison with sandy soils. Concerning climate factors, low temperature before grain harvest was found to increase DON; and high air humidity before harvest to increase HT-2. F. graminearum was negatively correlated with precipitation in July but correlated with air humidity before harvest. F. langsethiae was correlated with temperature in July. Total Fusarium increased with increasing precipitation in July. Organic cereal farmers have fewer cereal intense rotations than conventional farmers. Further, organic farmers do not apply mineral fertiliser or pesticides (fungicides, herbicides or insecticides), and have less problem with lodged fields. The study showed that these agronomic factors were related to the infestation of Fusarium species and the concentration of mycotoxins. Hence, it is reasonable to conclude that farming system (organic versus conventional) impacts Fusarium infestation, and that organic management tends to reduce Fusarium and mycotoxins. However, Fusarium infestation and mycotoxin concentrations may be influenced by a range of factors not studied here, such as local topography and more local climate, as well as cereal species and variety.

Less Fusarium infestation and mycotoxin contamination in organic than in conventional cereals.

A total of 602 samples of cereals, consisting of organically and conventionally produced barley, oats and wheat, were collected at harvest during 2002-2004 in Norway. Organic and conventional cereals were sampled in comparable numbers regarding cereal species, localisation and harvest time, and analysed for Fusarium mould and mycotoxins. Fusarium infestation and mycotoxin content were dependent on cereal species and varied year-by-year. However, in all cereal species, Fusarium infestation and levels of important mycotoxins were significantly lower when grown organically than conventionally. Concerning the most toxic trichothecenes, HT-2 and T-2 toxin, lower concentrations were found in organic oats and barley. Wheat was not contaminated by HT-2 and T-2, but lower concentrations of deoxynivalenol (DON) and moniliformin (MON) were found when organically produced. For mycotoxins considered to constitute the main risk to humans and animals in Norwegian cereals, i.e. HT-2 in oats and DON in oats and wheat, the median figures (mean levels in brackets) were as follows: HT-2 in organic and conventional oats were <20 (80) and 62 (117) microg/kg, DON in organic and conventional oats were 24 (114) and 36 (426) microg/kg, and DON in organic and conventional wheat were 29 (86) and 51 (170) microg/kg, respectively. Concentrations of HT-2 and T-2 in the samples were strongly correlated (r = 0.94). Other mycotoxins did not show a significant correlation to each other. Both HT-2 and T-2 concentrations were significantly correlated with infestation of F. langsethiae (r = 0.65 and r = 0.60, respectively). Concentrations of DON were significantly correlated with F. graminearum infestation (r = 0.61). Furthermore, nivalenol (NIV) was significantly correlated with infestation of F. poae (r = 0.55) and MON with F. avenaceum (r = 0.37). As lower Fusarium infestation and mycotoxin levels were found in organic cereals, factors related to agricultural practice may reduce the risk of contamination with Fusarium mycotoxins. Studies of these issues will be presented separately.

Automation of a clean-up procedure for determination of trichothecenes in cereals using a charcoal-alumina column.

Automation of the clean-up procedure for trichothecenes on a charcoal-alumina column is described. Standard high-performance liquid chromatographic equipment was used for the clean-up step. An acetonitrile-water (84 + 16, v/v) extract of the sample was cleaned up on a column packed with charcoal-alumina-Celite, which was washed with acetonitrile between each sample. The eluates were collected directly in reaction vials and evaporated to dryness. The residual water was removed azeotropically with benzene. The sample was derivatized with 1-(trimethylsilyl)imidazole and analysed by capillary gas chromatography with electron-capture detection.