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Fusarium head blight (FHB) is an important disease of wheat and the production of a wide spectrum of mycotoxins make it a major threat in most wheat- producing areas worldwide. This study aimed to identify the impact of epidemic FHB conditions on mycotoxin levels in unprocessed wheat. Therefore, Fusarium levels were monitored at two different locations in two treatments (natural infection and FHB inoculation) where 13 mycotoxins were evaluated by LC/MS-MS in six winter wheat varieties. In the current research, due to favourable climatic conditions for FHB infection during the flowering period at location Tovarnik, wheat varieties had higher disease severity and incidence, and consequently increased mycotoxin accumulation, compared to Osijek. The most abundant mycotoxins in FHB inoculated treatment, produced by Fusarium graminearum and F. culmorum were deoxynivalenol (DON), culmorin (CUL) and hydroxyculmorins. Derivatives of DON were found in lower concentrations, compared to DON. In treatment with natural infection DON did not exceed maximum limits set by EU, while in FHB inoculated treatment this limit was 10- and 15- fold increased at Osijek and Tovarnik, respectively. Aurofusarin levels were relatively high with an overall mean of 26822 μg kg-1 for all varieties on average at Tovarnik, compared to Osijek (5876 μg kg-1). At Osijek, nivalenol (NIV), hydroxyculmorins and 5-hydroxyculmoron occurred concomitantly with DON, while at Tovarnik DON was in high positive correlation with enumerated mycotoxins including 3 - acetyldeoxynivalenol (3- ADON). Varieties with higher initial susceptibility (El Nino, Tika Taka and Golubica) accumulated DON even in naturally infected samples at Tovarnik, where El Nino, as most FHB susceptible variety, accumulated 620 μg kg-1 of DON, and >1000 μg kg-1 of CUL and 15- hydroxyculmorin, respectively. These results highlighted the impact of environment variation in the production of Fusarium mycotoxins where FHB initial resistance had a higher impact on the accumulation of mycotoxins than general resistance. Furthermore, wheat samples with higher DON concentration also contained elevated levels of CUL and hydroxyculmorins, showing that CUL can have a possible role in Fusarium virulence. Under increased FHB disease pressure, one of the most abundant secondary metabolites was aurofusarin thus implying that there is a certain connection between the production of major Fusarium mycotoxins and pigments. |
