Alternaria and Fusarium in Norwegian grains of reduced quality--a matched pair sample study.

The occurrence and geographic distribution of species belonging to the genera Alternaria and Fusarium in grains of reduced and of acceptable quality were studied post-harvest in 1997 and 1998. A total of 260 grain samples of wheat, barley and oats was analysed. The distribution of Alternaria and Fusarium spp. varied significantly in samples of reduced quality compared with acceptable samples. Alternaria spp. dominated in the acceptable samples with A. infectoria group as the most frequently isolated and most abundant species group of this genus while Fusarium spp. dominated in samples of reduced quality. The most frequently isolated Fusarium spp. from all samples were F. avenaceum, F. poae, F. culmorum and F. tricinctum. Other important toxigenic Fusarium spp. isolated were F. graminearum and F. equiseti. The infection levels of F. graminearum and F. culmorum were significantly higher in the samples of reduced quality. The results indicated a negative interaction between F. graminearum and Alternaria spp. as well as between F. graminearum and other Fusarium spp.