Assessment of deoxynivalenol and deoxynivalenol derivatives in Fusarium graminearum-inoculated Canadian maize inbreds

The prevalence of maize, wheat and other cereal crops in Ontario, Canada, has led to frequent epidemics of ear rot and head blight disease caused by the broad host pathogen Fusarium graminearum. This fungus produces the trichothecene deoxynivalenol (DON) which is one of the most common mycotoxins contaminating food and feed globally and poses a risk to human and animal health. DON is commonly glycosylated by plant hosts into deoxynivalenol-3-glucoside (DON-3G) as part of a defence mechanism to detoxify and sequester mycotoxins. However, it has been documented that DON-3G can be hydrolyzed in the digestive system of animals, increasing the bioavailability of DON. There is a need for additional documentation of the incidence and ratio of DON-3G to DON in Canadian cereal crops. We investigated the occurrence and relative proportion of DON and modified DON compounds in Canadian-adapted maize germplasm with a wide range of ear rot tolerance. Forty-nine maize inbreds were manually challenged (kernel inoculation) with F. graminearum (15-ADON chemotype) as well as phenotyped for tolerance to Gibberella ear rot (GER) under field conditions. LC/MS was used to analyse 581 maize samples for DON, DON-3G, 15-ADON, and 15-ADON-3G. The DON-3G to DON mean molar ratio ranged from 3.1 to 19.7%. DON content was positively correlated with GER disease severity (r = 0.66, p < 0.01), while the DON-3G:DON molar ratio and disease severity were negatively correlated (r = -0.64, p < 0.001). Thus, GER-tolerant maize genotypes had relatively lower total DON content and higher DON-3G:DON ratios.