Evaluation of resistance to Fusarium head blight in wheat using different sources of inoculum

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.