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Two years of field sampling aimed to establish the predominance and association among the fungal pathogens causing Fusarium ear blight (FEB) in four European countries (Hungary, Ireland, Italy and the UK). A PCR-based method was used to detect four Fusarium species and two varieties of Microdochium nivale present in the samples. The prevalence of FEB pathogens differed significantly between countries. Overall, all pathogens were commonly detected in Ireland and to a lesser extent in the UK. In contrast, only two species, F. graminearum and F. poae, were regularly detected in Italy and Hungary. Fusarium culmorum was rarely detected except in Ireland. Log-linear models were used to determine whether there is the independence of the six FEB pathogens at each sampling site. Significant two-pathogen interactions were frequently observed, particularly in harvest samples; all these significant two-pathogen interactions were of the synergistic type, except between F. poae and F. culmorum, and were generally consistent over the 2 years and four countries. Fusarium graminearum and F. poae were least frequently involved in two pathogen interactions but were involved in most of the nine significant three-pathogen interactions. However, only the interaction between F. graminearum, F. avenaceum and F. poae was significant in both years. Potential implications of the present results in FEB management are discussed.

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.

No abstract

The effect of small temperature differentials (16 vs. 20 ° C) on the pathogenicity of deoxynivalenol producing single isolates of Fusarium culmorum and F. graminearum and on the fusarium head blight (FHB) response of eight wheat cultivars was examined. Fusarium culmorum inoculation 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. graminearum inoculation 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 both F. culmorum and F. graminearum inoculations 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 for F. graminearum inoculation, 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).