Species diversity of Fusarium head blight and deoxynivalenol (DON) levels in Western Canadian wheat fields

Fusarium head blight (FHB) is primarily caused by Fusarium graminearum and is the most destructive wheat disease in western Canada. The trichothecene toxin deoxynivalenol (DON) and its derivatives 3-ADON and 15-ADON, which are produced by Fusarium, are toxic to humans and livestock. This study aimed to evaluate the Fusarium species and trichothecene-producing genotypes present in producer wheat fields of western Canada in 2019 and 2020. The grain analysis for DON showed that samples collected from both years experienced mild levels of FHB toxin contamination. In spring wheat, the highest mean DON content was recorded from Saskatchewan samples (0.9 ppm) in 2019 and Manitoba samples (0.3 ppm) in 2020. Winter wheat samples had lesser mean DON levels (<0.2 ppm) for all three provinces in both years. The chaff collected from the same spring wheat heads showed a significantly higher DON content than the grain in both years (P < 0.1 for 2019 and P < 0.001 for 2020), suggesting that chaff should be tested for DON before use as livestock feed. Most samples collected were infected by F. graminearum, with the highest F. graminearum percentage observed in the spring wheat from Manitoba. Further, F. avenaceum, F. sporotrichoides, F. culmorum, F. poae and F. acuminatum were found in infected samples. Most of the F. graminearum isolates were of the 3ADON genotype, which is the dominant genotype in FHB disease in western Canada. The study indicated that 3ADON-producing F. graminearum is becoming more frequent in western Canadian fields than the 15ADON genotype.