Trichothecenes and aggressiveness of Fusarium graminearum causing seedling blight and root rot in cereals

Greenhouse trials conducted in 2003 and 2004 investigated the impact of trichothecenes on the severity of seedling blight and root rot in common wheat (Triticum aestivum), durum wheat (Triticum turgidum var. durum), barley (Hordeum vulgare) and triticale (xTriticosecale 6x) using two trichothecene-producing and two trichothecene-nonproducing Fusarium graminearum strains. In 2003 seedling emergence and survival following soil infestation of the trichothecene-producing strain (Gz3639) were significantly reduced compared with the trichothecene-nonproducing strain (GzT40), while root-rot incidence and severity were increased significantly. In 2004, two trichothecene-producing strains (Gz3639 and GzT106) reduced seedling emergence and survival (P <= 0.01) in eight of 10 crops/cultivars based on single-degree-of-freedom contrasts. However, when results from all strains were combined no significant differences were observed between two trichothecene-producing and two trichothecene-nonproducing F. graminearum strains. Inoculation with GzT106, a trichothecene-producing 'add-back' strain, resulted in more severe root rot symptoms in eight of 10 cultivars (P <= 0.01-0.05) and lower seedling emergence and survival in seven of 10 cultivars (P <= 0.01-0.10), compared with the wild-type parental strain Gz3639. The presence of trichothecenes may play an important role in the aggressiveness of F. graminearum.