Production of fusarielins by Fusarium

Fusarielins constitute a relative unexplored group of secondary metabolites, which have been isolated mainly from unidentified Aspergillus and Fusarium strains. In the present study we show that the ability to produce fusarielins is restricted to a few Fusarium species. Among the 15 analyzed species fusarielins were identified only in extracts from Fusarium graminearum and Fusarium tricinctum. The influence of different carbon sources on fusarielin biosynthesis was examined and the results showed that disaccharides and dextrin in combination with arginine as sole nitrogen source increased fusarielin production. When arginine was replaced with nitrate the fusarielins were produced on a wider selection of carbon sources including all monosaccharides. Production of fusarielins in F. graminearum was also influenced by pH, cultivation time, temperature and fructose concentration with the optimal conditions being: pH 6, 25 °C, 26 days and 60 mg fructose/mL. Wheat spikes were inoculated with F. graminearum to determine whether fusarielins are produced in infected cereals and fusarielin H was detected in all samples ranging from 392 to 1865 ng/g (mean: 989 ng/g) indicating that fusarielins are produced during infection. The study shows that even though fusarielins are produced by a narrow list of Fusarium species, they potentially can be present in infected cereals.