Assessment of Fusarium infection in wheat heads using a quantitative PCR assay
Résumé
Accuracy of a qPCR assay in quantifying the DNA of trichothecene-producing F. culmorum and F. graminearum within harvested wheat grains and head tissue was evaluated in comparison with incidences of infected kernels and deoxynivalenol (DON) levels. In a first experiment six durum and bread wheat varieties were grown in randomized plots for a 2-year period, and inoculated with Fusarium macroconidia at six growth stages between heading and dough ripening, to obtain a wide range of Fusarium head blight (FHB) incidences. There was a close relationship between fungal DNA and amount of DON, and this relationship was consistent over Fusarium species, wheat species and varieties, and over a wide range of FHB infection. In a second experiment potted wheat plants were grown under environment-controlled conditions and inoculated with the two Fusarium species at full flowering; head samples were collected before inoculation and after 6 hours to 12 days, and processed by the qPCR assay. This assay made it possible to detect the dynamic of fungal invasion in planta after infection had occurred, and to single out the presence of infection before onset of the disease symptoms: a robust detection of the infection occurred within 18 to 24 hours for F. culmorum, and within 2 to 9 days for F. graminearum.
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