Fusarium species pathogenic to barley and their associated mycotoxins

Epidemics of Fusarium head blight (FHB) occurred on barley in Minnesota, No rth Dakota, and South Dakota from 1993 to 1998. The Red River Valley region was most severely impacted by the disease based on assessments of FHB seve rity in grain samples harvested from commercial fields. Fusarium graminearu m was the primary pathogen causing these FHB epidemics. It comprised from 6 2 to 64% of all Fusarium species isolated from infected kernels from 1994 t o 1996. Fusarium pone (range of isolation 13 to 20%), F. sporotrichioides ( 10 to 17%), and F. avenaceum (6 to 10%) also were isolated from barley kern els and were likely involved in causing some FHB infection, but to a very l imited extent. All four Fusarium species were pathogenic on barley in inocu lation tests conducted in both the greenhouse and the field. Mycotoxin scre ens were performed on barley spikes inoculated with the respective species in the greenhouse. Spikes infected with F: graminearum contained deoxynival enol and 15-acetyldeoxynivalenol; those infected with F. sporotrichioides c ontained T-2 toxin, HT-2 toxin, and T-2 tetraol; and those infected with F. pone contained nivalenol. Some isolates of F: pone also produced 15-acetox yscirpenol and scirpentriol. Although F. graminearum and DON are recognized as the primary FHB pathogen and mycotoxin, respectively, in barley, the po ssible presence of other Fusarium species and mycotoxins should not be over looked.