Fusarium Head Blight (FHB) is a destructive disease of small grain cereals and a major food safety concern. Epidemics result in substantial yield losses, reduction in crop quality, and contamination of grains with trichothecenes and other mycotoxins. A number of different fusaria can cause FHB, and there are significant regional differences in the occurrence and prevalence of FHB pathogen species and their associated mycotoxins. Information on FHB pathogen and mycotoxin diversity in Mexico has been extremely limited, but is needed to improve disease and mycotoxin control efforts. To address this, we used a combination of DNA sequence-based methods and in-vitro toxin analyses to characterize FHB isolates collected from symptomatic wheat in Mexico during the 2013 and 2014 growing seasons. Among 116 Fusarium isolates, we identified five species complexes including nine named Fusarium species and 30 isolates representing unnamed or potentially novel species. Significant regional differences (P < 0.001) in pathogen composition were observed, with F. boothii accounting for >90% of isolates from the Mixteca region in southern Mexico, whereas F. avenaceum and related members of the F. tricinctum species complex (FTSC) accounted for nearly 75% of isolates from the Highlands region in Central Mexico. F. graminearum, which is the dominant FHB pathogen in other parts of North America, was not present among the isolates from Mexico. F. boothii isolates had the 15-acetyldeoxynivalenol toxin type, and some of the minor FHB species produced trichothecenes, such as nivalenol, T-2 toxin and diacetoxyscirpenol. None of the FTSC isolates tested was able to produce trichothecenes, but many produced chlamydosporol and enniatin B.

A two-year (2018/19 and 2019/20) field experiment was carried out to evaluate the efficacy of recently developed fungicide combinations (with different modes of action) towards fungal diseases on seven bread and eight durum wheat varieties. The trial was performed at the FIELDLAB experimental station of the University of Perugia (Italy). The diseases were assessed under natural pressure except for Fusarium head blight (FHB) for which artificial inoculation with a Fusarium culmorum deoxynivalenol (DON)-producing strain was performed at the full flowering stage (BBCH 65). Fungicides were sprayed at the fully extended flag leaf (BBCH 39) and full flowering (BBCH 65) stages. The incidence of different fungal diseases was visually evaluated and other parameters [grains production (t/ha), protein content (%), test weight (kg/hL), and DON accumulation in grain (μg/kg)] were also determined. In the two years, characterized by different climatic conditions, the fungicide treatments showed efficacy in controlling the observed diseases (Septoria tritici blotch and FHB) as well as in reducing DON contamination. No significant differences were found between treatments. The results highlight that, in the present scenario of commercially available durum and bread wheat varieties, the timely application of the most common fungicides plays a crucial role for FHB and DON management in the presence of climatic conditions that are favorable to the disease. The impact of these results in an integrated disease management perspective is discussed.

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The wheat pathogen Zymoseptoria tritici can respond to light by modulating its gene expression. Because several virulence-related genes are differentially expressed in response to light, different wavelengths could have a crucial role in the Z. tritici–wheat interaction. To explore this opportunity, the aim of this study was to analyze the effect of blue (470 nm), red (627 nm), blue–red, and white light on the in vitro and in planta development of Z. tritici. The morphology (mycelium appearance, color) and phenotypic (mycelium growth) characteristics of a Z. tritici strain were evaluated after 14 days under the different light conditions in two independent experiments. In addition, bread wheat plants were artificially inoculated with Z. tritici and grown for 35 days under the same light treatments. The disease incidence, severity, and fungal DNA were analyzed in a single experiment. Statistical differences were determined by using an ANOVA. The obtained results showed that the different light wavelengths induced specific morphological changes in mycelial growth. The blue light significantly reduced colony growth, while the dark and red light favored fungal development (p < 0.05). The light quality also influenced host colonization, whereby the white and red light had stimulating and repressing effects, respectively (p < 0.05). This precursory study demonstrated the influence of light on Z. tritici colonization in bread wheat.

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