Fusarloses of barley with emphasis on the content of trichothecene

The infestation of barley grains by fungi of the genus Fusarium was studied on malting barley from Kromei'iz (360 samples) and one sample from Kojet!n in Czech Republic. Most frequent species in the season 1997-1998 were: F. culmorum (over 70% of the isolates), F. poae (over 20% of the isolates), F. avenaceum (over 2%). Much less frequent were: F. stilboides v. stilboides, F. aqaeductum v. aqaeductum, F. merismoides v. merismoides and F. gigas. The isolates of F. culmorum were highly pathogenic when barley was artificially inoculated; those of F. poae had low pathogenity. Five varieties of spring barley at growth stage 1-5 on the Feekes scale reacted to F. culmorum as follows: I) Tolar (most resistant), 2) Akcent, Lumar and Rubfn (intermediate), 3) Krona (most susceptible). An application of fungicides on a plot inoculated with F. avenaceum and F. graminearum increased the yield of grain by 0.46 to 1.71 t/ha. Most effective fungicides against the pathogens were: metconazole, tebuconazole and prochloraz. The effect of the combination tebuconazole + triadimefon + prochloraz was found to be most effective. For determi­ nation of six trichothecene mycotoxins in fungal mycelium, macroconidia and spring barley, high resolution capillary gas chro­ matography with electron capture detection was used. Only toxin T-2 and nivalenol (NIV) were detected in fungal mycelium, and a low level of NIV was found in spring barley, variety Rubfn (lower than legislated limit- 2 mglkg of cereals).