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Newly discovered fusariotoxins

In a 2010 survey on wheat in North America, new strains of Fusarium graminearum were isolated and identified as 3-ADON-producing genotypes, though they were not producing any known mycotoxin. In a separate study conducted on rice cultures, it was confirmed that the newly isolated F. graminearum strains were not producing any known mycotoxins. These strains had also been considered for use as biocontrol for DON-producing mold strains.

The aim of a recent study conducted by Varga et al. (2015) was to determine if these new F. graminearum strains could produce novel mycotoxins, as there were clear signs of plant disease in their presence. This resulted in the discovery of a new Type A trichothecene called NX-2, which has toxicity comparable to 3-ADON. When wheat ears were inoculated with the new isolated mold strain that produces NX-2, its deacetylated form, NX-3, was also discovered, with 10 times higher contamination than NX-2. NX-3 was shown to inhibit protein synthesis at a level similar to DON. Further, Varga et al. were also able to produce the mycotoxin NX-4, which has a structure similar to 15-ADON; it is not known whether NX-4 can be produced in natural conditions.

Information on the prevalence of these new strains of molds in raw materials is limited. In a survey conducted in US wheat growing areas (Minnesota, and North and South Dakota), strains responsible for NX-2 production were detected in only 3 % of the samples. There are no data on the prevalence of these new strains of F. graminearum in Europe or other parts of the world, nor on the frequency and level of contamination of the novel mycotoxins in cereals. The reservoir for NX-2 producing F. graminearum can be non-agricultural plants, as some strains (02-264) were detected in non-agricultural grasses.

Following the discovery of new mold strains and trichothecene mycotoxins, more research is needed to assess the risk associated with them (occurrence, toxicity, etc.).

More information: New tricks of an old enemy: isolates of Fusarium graminearum produce a type A trichothecene mycotoxin (E. Varga, G. Wiesenberger, C. Hametner, T.J. Ward, Y. Dong, D. Schöfbeck, S. McCormick, K. Broz, R. Stückler, R. Schuhmacher, R. Krska, H.C. Kistler, F. Berthiller, G. Adam).