LAUSR

Abstract Aggressiveness assessment of Fusarium head blight (FHB) is crucial for explaining the interaction in FHB–wheat association. Currently, in vitro tools have proved to be very useful in identifying disease responses in wheat to FHB infection. To update our knowledge, intra- and inter-species variability of the aggressiveness was studied in 16 isolates of four FHB species (F. culmorum, F. solani, F. verticillioides and F. equiseti) using an in vitro Petri-dish test. Three aggressiveness criteria, germination rate reduction, standardised area under disease progress curve (AUDPCstandard) and coleoptile length reduction, were evaluated on a durum wheat cultivar showing a moderate level of quantitative resistance. Regarding AUDPCstandard, intra- and inter-species variability was detected. The other two aggressiveness criteria did not distinguish isolates within and among species. The three aggressiveness criteria were not significantly correlated. However, it was not possible to cluster the isolates based on their species origins because of similarity in pathogenic level among the 16 fungal isolates. The results provide evidence that there is a differential interaction between quantitative resistance genes in wheat plants and the 16 tested FHB isolates. The values of AUDPCstandard showed significant correlation with both: disease incidence and disease severity obtained under controlled conditions (r = 0.627** and r = 0.539*, respectively), and disease incidence generated by field conditions (r = 0.525*). AUDPCstandard could be of potential use in evaluating the aggressiveness of FHB in adult wheat plants under controlled and field conditions.