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In Germany, maize is one of the most important agriculture commodities, a major component in animal feed as well as an essential substrate producing biogas. Maize ear rot poses a major impact worldwide as it is caused by several Fusariumspp., most of which have the ability to produce mycotoxins. Despite of the expansion of the maize acreage in recent years, limited information is available concerning the incidence of Fusarium ear rot in Germany. Therefore, in a two-year survey maize crops were sampled in the major maizeproducing areas in Germany to establish the severity of Fusarium ear rot and the biodiversity of Fusariumspecies. In 2006, the frequency of kernels infected by Fusariumspp. ranged from 0.7 % to 99.7 %; the average incidence was 32.4 %. Thirteen Fusariumspecies were isolated from maize kernels, with F. verticillioides, F. graminearumand F. proliferatumbeing the predominant species. In 2007, the highest incidence of Fusarium ear rot was 64 %; the mean level of infection was 21.7 %. F. graminearumwas by far the most frequent species isolated from all sampled fields in 2007. In addition, F. crookwellense, F. subglutinansand F. avenaceumwere also frequently isolated. In particular, the fumonisin-producing species F. verticillioidesan F. proliferatumwere less frequent than in 2006. The year-to-year variability in the frequency of Fusariumspecies and in the overall infection rate may be explained by significant differences in temperature and precipitation during the growth periods.

Transposon mutagenesis was applied to generate mutants in Fusarium graminearum. The mimp1/impalasystem originally identified in F. oxysporumproved very promising for mutagenesis as the transposon and reinserted at high frequency in (the vicinity) of genes. A collection of mutants was screened for growth, for pathogenicity and for perithecia production. Several mutants blocked in one or more functions were obtained. The wild-type phenotype of one such mutant could be restored by complementation with a non-disrupted copy of the gene. In addition reinsertions occurred on each of the four chromosomes of F. graminearum, making this system a powerful tool in the functional analyses of the > 10,000 genes predicted in the F. graminearumgenome.