A physiological and molecular approach for studying the interaction among DON-producer Fusarium graminearum isolatesand tolerant or susceptible varieties of Triticum haestivum

Fusarium graminearum can cause Fusarium head blight (FHB) of wheat, leading to a severe reduction of grain yield and quality. The virulence factor involved in FHB disease is the production of toxins, predominantly deoxynivalenol (DON) which inhibits the activity of some plant defence proteins and induces a resistant response in tolerant varieties such as hydrogen peroxide production and the onset of programmed cell death. One of the biochemical mechanisms of resistance to DON is the plant ability to convert DON in a less toxic glucosylated form, via a reaction carried out by glucosyl-transferase. In this study, we analysed by a SYBR green RT-PCR approach the expression of different genes, whose products are involved in the interaction of tolerant or susceptible early flowering-soft wheat varieties with both a DON or a DON-zearalenone (ZEA) producer strains of F. graminearum. The fungal genes analysed encode proteins putatively involved in the onset of disease progression such as an exopolygalacturonase (ePG1) related to plant cell wall degradation, an orthologue of yAP-1, that is a yeast transcription factor active in the cell defence against oxidative stress, and Tri6, one of the thricotecenes biosynthesis regulator. In order to correlate the tolerant and susceptible phenotype of the two Triticum aestivum varieties with some of plant defence-related activities, the analysis of expression of three genes which encode glucosyl transferases and the pathogenesis- related protein PR1 have been carried out. Furthermore, we have analyzed, by LC-MS, DON and derivatives extracted from infected wheat. The aim of this work was to find a correlation between the expression of some F. graminearum genes involved in the onset of the FHB disease with the different ability of tolerant and susceptible varieties of T. aestivum to achieve DON inactivation.