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Susceptibility of eight commercial European wheat cultivars to fusarium head blight (FHB) disease caused by Fusarium graminearum, F. culmorum, F. poae and Microdochium nivale (formerly known as Fusarium nivale) was compared under controlled environment conditions (16°C). FHB did not differentially affect cultivars in terms of disease symptoms, fungal DNA content of grain or deoxynivalenol (DON) contamination. However, the Hungarian-grown cultivars GK-Othalom and Fatima 2 (of Romanian origin) showed greater type V resistance (yield tolerance) to FHB than did the others. Also, nivalenol was produced by F. poae in these two cultivars and in Italian cultivar Norba, but not in other cultivars. Overall, significant relationships were found between the FHB and seedling blight resistance in vitro of these eight cultivars, but such relationships were generally highly dependent on cultivar, and therefore it is likely that the in vitro test is at best measuring components of FHB resistance and/or genotype-specific resistance components. [ABSTRACT FROM AUTHOR]

The effect of small temperature differentials (16 vs. 20°C) on the pathogenicity of deoxynivalenol producing single isolates ofFusarium culmorumandF. graminearumand on the fusarium head blight (FHB) response of eight wheat cultivars was examined.Fusarium culmoruminoculation caused greater visual disease symptoms at 20°C than at 16°C, both overall and on an individual cultivar basis (overall AUDPC = 13·5 and 9·6, respectively) (P < 0·05). In contrast,F. graminearuminoculation caused greater overall visual disease symptoms at 16°C than at 20°C, both overall and at the individual cultivar level (overall AUDPC = 12·8 and 10·9, respectively) (P < 0·05). Results showed bothF. culmorumandF. graminearuminoculations caused a greater loss in yield at 20°C (54·3 and 46·9% relative 1000-grain weight, respectively) compared with 16°C (73·3 and 66·9% relative 1000-grain weight, respectively) (P < 0·05).Fusarium culmorum-inoculated heads contained similar amounts of fungal DNA at both 16 and 20°C (1·9 and 1·7 ng mg−1 of plant material, respectively) (not significant), while forF. graminearuminoculation, plants contained higher amounts of fungal DNA at 20°C (2·0 and 1·0 ng mg−1 of plant material, respectively) (P < 0·05). Overall, there was a significant negative correlation between AUDPC and percentage relative 1000-grain weight at both 16 and 20°C (r =−0·693 and−0·794, respectively,P < 0·01). [ABSTRACT FROM AUTHOR]

Over 4 years, the environmental conditions and the causal agents of Fusarium head blight (FHB) disease of wheat were determined in field sites in four European countries: Hungary, Ireland, Italy, and the United Kingdom. Polymerase chain reaction-based methods were used to detect each species causing FHB and quantify its DNA (as a measurement of fungal abundance) in the samples. Canonical correspondence analysis (CCA) was used to determine the relationship of the incidence and abundance of each species with weather variables. CCA indicated that little variability in the species prevalence data was explained by the weather variables. In contrast, a greater proportion of variability in abundance data was accounted for by the weather variables. Most samples contained two or more species and statistical analysis suggested that these species tended to coexist at field sites. CCA also indicated that there were differences in the relationships of the prevalence and abundance of the six FHB species with environmental variables. Fusarium poae was associated with relatively drier and warmer conditions, whereas F. graminearum was associated with warmer/humid conditions. F. avenaceum and F. culmorum were both associated with niches of cooler/wet/humid conditions. Two Microdochium species were associated with regions of relatively cool/moderate temperatures and frequent rainfalls of short duration. The results also suggested that environmental conditions differentially affect the infection and colonization processes, and the comparative abundance of the six species. [ABSTRACT FROM AUTHOR]