Reduced mycotoxin accumulation in native barley from the Brazilian Pampa despite colonization by the Fusarium sambucinum species complex.

Abstract

The present study examined Fusarium diversity and mycotoxin occurrence in 54 native barley samples from the Pampa biome in Rio Grande do Sul State. Fusarium isolates clustered primarily within the F. graminearum clade, which is part of the F. sambucinum species complex. Additionally, F. armeniacum, a potential T-2 toxin producer, and other species belonging to the F. heterosporum and F. tricinctum species complexes were found. Genome sequencing of four isolates (two F. asiaticum, F. cortaderiae, and F. armeniacum) revealed syntenic trichothecene and zearalenone gene clusters. However, no mycotoxin production was detected under the studied conditions. Mycotoxin levels in the native barley were low, especially when compared to barley from agroecosystems within the same region. Deoxynivalenol-3-glucoside (D3G) was the most prevalent, followed by 3-acetyldeoxynivalenol (3-ADON), deoxynivalenol (DON), nivalenol (NIV), and zearalenone (ZEN). In contrast, 15-acetyldeoxynivalenol (15-ADON) was not detected. These findings suggest that the well-balanced fungal community in natural ecosystems may exert less selective pressure, resulting in decreased mycotoxin production. The results also indicate that native barley can metabolize DON into less toxic compounds, such as D3G. Nevertheless, native barley may still serve as a reservoir for toxigenic Fusarium species. Monitoring these populations is important for anticipating shifts in pathogen dynamics amid agricultural expansion and climate change. Additionally, native barley may provide genetic resources for developing more resistant cereals, contributing to sustainable agriculture and food safety.