The response of four winter wheat cultivars, differing in resistance to Fusarium head blight (FHB), to spray inoculation with four selected Fusarium graminearum isolates, mixture of these isolates and frequently used F. culmorum isolate B was studied in five field and glasshouse experiments during 2008-2010. Analyses of variance showed highly significant main and interaction effects of cultivar, inoculum source and environment (year-trial) on all five examined traits indicative of disease severity, yield loss and accumulation of mycotoxins. The relations between traits were not evidently influenced by the used isolate. Resistance of host genotypes and environmental conditions accounted for a greater proportion of the total variation (8-36%) than the inoculation source (isolate) that substantially influenced the accumulation of the mycotoxin deoxynivalenol (12%), but expressed relatively low effects on symptom scores, percentage of fusarium damaged kernels and reductions of yield components (2-4%). Two-way and three-way interactions accounted for 25-40% of variation in the examined traits, which indicates great importance of multi-environment tests, using different Fusarium isolates for inoculation. Separate inoculation with F. graminearum isolates, differing in aggressiveness, did not appear to be more advantageous than their use in mixture that showed medium or below-average aggressiveness in all traits. The application of an isolate mixture could be recommended as a "less costly" alternative to inoculation with single isolates in trials repeated in different years and/or locations. It was indicated by these experiments that especially the detection of resistance/moderate resistance to FHB could be facilitated by the use of a carefully selected mixture of isolates. However, the application of aggressive isolates (isolate B of F. culmorum in these experiments) appeared to be beneficial to eliminate FHB susceptible materials in the breeding process.

Fusarium head blight (FHB) is the most important disease of wheat in Central Europe. Although common resistance of wheat against several Fusarium species has been proposed recently, no data were available for the recently described species/lineages of F. graminearum and F. culmorum. In this study, twenty wheat genotypes were tested under field conditions by spraying inocula of isolates of eight species of the F. graminearum species complex, and three lineages of F. culmorum in 2003-2004. The severity of FHB, Fusarium damaged kernels, yield reduction and deoxynivalenol/nivalenol contamination were measured. F. culmorum isolates were in general more aggressive to wheat than those belonging to the F. graminearum species complex. The various wheat genotypes exhibited similar reactions against the different Fusarium isolates, indicating that resistance to F. graminearum sensu stricto was similar to that for the other species of the F. graminearum species complex examined. This is an important message to breeders as the resistance relates not only to any particular isolate of F. graminearum, but similarly to isolates of other Fusarium species.