Fungal diversity and natural occurrence of deoxynivalenol and zearalenone in freshly harvested wheat grains from Brazil

• The predominant FGSC members isolated were F. meridionale and F. graminearum s.s.
• Sao Paulo State was highly contaminated with Microdochium nivale (23%).
• Deoxynivalenol was found in 99% of the samples analyzed.
• Zearalenone was found in 82% of wheat grains from Rio Grande do Sul.

This study investigated the fungal diversity and presence of deoxynivalenol and zearalenone in 150 samples of freshly harvested wheat grains collected in three regions of Brazil (Sao Paulo, Parana, and Rio Grande do Sul). Analysis of the mycobiota showed a predominance of Alternaria sp., Fusarium sp. and Epicoccum sp. Microdochium nivale (23%), a fungus rarely found in Brazilian crops, was detected in Sao Paulo. Four members of the Fusarium graminearum species complex were isolated: F. graminearum s.s. (37%), Fusarium meridionale (46%), Fusarium cortaderiae (13%), and Fusarium austroamericanum (3%). Toxin analysis revealed 99% contamination with deoxynivalenol (mean 706 μg/kg). The frequency of zearalenone varied greatly across regions: wheat grains from Rio Grande do Sul (84%) and Sao Paulo (12%) had median concentrations of 70.9 and 57.9 μg/kg, respectively. ZEA was not detected in the samples from Parana. A total of six samples were above the maximum tolerated level recommended by the European Commission for ZEA in wheat grains. This study provided new insights into the natural mycobiota of Brazilian wheat, demonstrating contamination of most samples with deoxynivalenol and high frequency of zearalenone in samples from Rio Grande do Sul.