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SummaryFusarium species infect cereal crops all over the world and cause the important diseases Fusarium head blight and crown rot in wheat. Fusarium pathogens reduce yield and some species also produce trichothecene mycotoxins, such as deoxynivalenol (DON), during infection. These toxins play roles in pathogenesis on wheat and have serious health effects if present in grain consumed by humans or animals. In this study, the response of wheat tissue to DON has been investigated. Infusion of wheat leaves with DON induced hydrogen peroxide production within 6h followed by cell death within 24h that was accompanied by DNA laddering, a hallmark of programmed cell death. In addition, real-time PCR analysis revealed that DON treatment rapidly induced transcription of a number of defence genes in a concentration-dependent manner. Co-treatment with DON and the antioxidant ascorbic acid reduced these responses suggesting their induction may be at least partially mediated by reactive oxygen species (ROS), commonly known to be signalling molecules in plants. Wheat defence genes were more highly expressed in wheat stems inoculated with a DON producing fungal strain than those inoculated with a DON-nonproducing mutant, but only at a late stage of infection. Taken together, results are consistent with a model where DON production during infection of wheat induces ROS, which on one hand may stimulate programmed host cell death assisting necrotrophic fungal growth, but on the other hand the ROS may contribute to the induction of anti-microbial host defences.3

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