Fusarium head blight (FHB) is a horribly destructive fungal diseases of barley. FHB is caused by a species complex of Fusaria, of which Fusarium graminearum Schwabe is the main causal species of FHB epidemics in Canada. Field surveys show that two or more Fusarium species often co-exist within the same field or grain sample and F. poae is reported as another important species in barley in Ontario and Quebec. The aim of this study was to observe the pathogenicity of F. graminearum, F. poae and a co-inoculation of both species causing FHB in barley. Two susceptible barley cultivars were spray-inoculated at 10 to 14 days after heading. Phenotypic disease severity was rated on a scale of 0-9 at 4, 7, 14, 21, and 28 days after inoculation. There was a significant difference in FHB severity between F. graminearum and F. poae, where infection with F. graminearum produced more severe disease ratings. F. poae generated lower disease ratings and was not statistically different from the control. When heads were co-inoculated with both Fusarium species, the resulting FHB severity was unchanged 54relative to heads inoculated with F. graminearum only. The ratio of F. graminearum to F. poae genomic DNA was also no different than when heads were inoculated with F. graminearum alone, as quantified with ddPCR using markers specific to each species. Metabolomic analysis of sample extracts corroborated our other findings where F. graminearum appeared to outcompete F. poae in barley also at the mycotoxin level. Barley cultivar did not have a significant effect on visual FHB disease ratings and fungal DNA detection, however there were some chemical differences between cultivars in response to challenge by both F. graminearum and F. poae.

La fusariosi della spiga è tra le malattie del grano più distruttive e diffuse al mondo. Alcune specie responsabili di questa malattia sono micotossigene. Ci sono state segnalazioni della presenza di nivalenolo (NIV) e tossine T-2 e HT-2 nel nord Italia, micotossine prodotte da Fusarium poae, F. sporotrichioides e F. langsethiae. I limiti massimi di T-2 e HT-2 ammessi nei cereali non trasformati e nei prodotti a base di cereali non sono ancora stati individuati (Regolamento CE 856/2005). Il programma di dottorato del candidato è inserito in questa linea di ricerca. Sono stati condotti studi in vitro sulla biologia ed ecologia dei funghi produttori di NIV, T-2 e HT-2, considerando quattro isolati di F. poae, due di F. sporotrichioides e due di F. langsethiae. Le prove hanno riguardato la crescita delle colonie, la produzione di spore, la loro germinazione e la produzione di micotossine. La gravità dell'infezione, l'invasione (quantità di DNA nelle spighe), la resa in granella e la produzione di tossine sono state misurate a diversi tempi, temperature (in planta) e stadi fenologici (in campo) dopo l'inoculazione artificiale. Al fine di verificare l'attendibilità dei dati, tutti gli esperimenti in planta e in campo sono stati ripetuti per due anni. / The Fusarium head blight is one of the most destructive diseases of wheat in different parts of the world. Some of the species responsible for Fusarium head blight are potentially mycotoxigenic. There are reports of nivalenol (NIV), T-2 toxin and HT-2 in northern Italy. These are metabolites produced by F. poae, F. sporotrichioides, and F. langsethiae. The maximum limits of T-2 and HT-2 permitted in unprocessed cereals and cereal-based products, included in EC Regulation 856/2005 has not been identified. The PhD program of the candidate is placed in this line of the research. In vitro studies conducted on the biological and ecological of pathogenic fungi producer NIV, T-2 and HT-2 including four isolates of F. poae, two of F. sporotrichioides and two isolate of F. langsethiae. Tests were carried out to investigate the conidia germination, colony growth, spore production and mycotoxins production. The infection severity, invasion (amount of DNA in spikes), grain yield and toxin production were measured at different temperatures, different time (in planta) and different growth stages (in field) after artificial inoculation.