The effect of biological control on mycotoxin concentrations and the mycobiome in durum wheat grain and stems

The present study was undertaken to determine the effect of the durum wheat mycobiome on pathogens and mycotoxin concentrations in grain, and to examine the causes of necrosis in durum wheat grown after durum wheat. The severity of Fusarium head blight (FHB) was most effectively reduced (by 79.9%) by two applications of Debaryomyces hansenii. The biocontrol treatment did not decrease the prevalence of the following fungal species of the genus Fusarium, which were isolated from grain: F. avenaceum (2-18.7%), F. culmorum (2.7–14%), F. graminearum (2.7–28%), F. oxysporum (2–8%), F. poae (2-18.7%), and F. sporotrichioides (2–12%). The application of D. hansenii reduced deoxynivalenol (DON) levels in grain by up to 59.9%. Fungi were identified by next-generation sequencing (NGS), which revealed the presence of eight species of the genera Fusarium and Gibberella, which accounted for 27.8% of the total number of operational taxonomic units (OTUs), as well as 25 yeast species that represented 2.4% of total OTUs. The biocontrol treatment did not reduce the number of OTUs associated with the dominant species of the genera Fusarium and Alternaria, and considerably increased the number of OTUs associated with autochthonous yeasts. Durum wheat necrosis was caused by Fusarium fungi, mainly F. avenaceum. The application of D. hansenii suppressed symptoms of FHB, decreased the content of Fusarium mycotoxins in grain, but did not inhibit grain colonization by Fusarium pathogens.