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Septoria tritici blotch (STB) disease of wheat is caused by the fungal pathogen Zymoseptoria tritici. It is the most important foliar disease of wheat in western Europe and affects wheat cultivation worldwide. The combination of intensive fungicide usage, a polycyclic asexual life cycle and an active sexual cycle has led to the emergence of fungal strains resistant/tolerant to all the major classes of fungicides used in its control. The hallmark of this disease is a long, symptomless latent phase that precedes the onset of visible symptoms. Understanding the processes that occur during the symptomless phase of infection is paramount in developing alternative strategies for disease control; however, large gaps in our knowledge of the disease remain. The known unknowns of the latent stage of infection can be summarized in three questions. Does the fungus initiate or manipulate host defences to trigger programmed cell death in order to facilitate nutrient acquisition or is the host acting exclusively? Does the fungus feed during both the latent phase and the necrotrophic phase like a true hemibiotroph? Does the long latent phase serve a beneficial function for the fungus or is it simply an artefact of evolution? This review aims to distil observations made during studies that have directly or indirectly contributed to answering these questions and points towards their most likely answers. [ABSTRACT FROM AUTHOR]

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]