Fusarium langsethiae in Italy: geographical distrbution, pathogenicity and toxin production.

It has been assessed that one of the main virulence factor involved in theFusarium head blight (FHB) disease of wheat leading to a severe reduction ofgrain yield and quality is the production of toxins, predominantly deoxynivalenol(DON) in F. graminearum. This toxin delays germination and growth of wheat plants(Champeil, et al., 2004), inducing hydrogen peroxide (H2O2) production, inhibitingprotein synthesis and stimulating cell death in planta (Desmond et al., 2008).Mycotoxigenic fungi contamination is a real issue, especially for cerealindustry. Therefore, in order to reduce the diffusion of plant disease and health risksdue to DON toxicity, there is a real need to develop analytical methods able to identifyDON-producing fungal variety and to quantify mycotoxins at an early stage of fungalcontamination and in order to accomplish this need we intend to study the interactionbetween F. graminearum and T. aestivum kernels.In this work, the interaction between two Triticum aestivum varieties, Blasco(tolerant) and Sagittario (susceptible), inoculated with two F. graminearum strains(Fg126 and Fg8308), was studied. Two primer pairs (N1-2) designed by Konietznyet al. (2003), on the gene sequences belonging to the thricothecene gene cluster wereused to assess the level of DON production ability of our Fusarium strains throughPCR method. The same primers were used for developing a SYBR green RealTime-PCR assay for quantifying the DNA of F. graminearum strains in artificiallycontaminated soft wheat. The results obtained indicate a different ability of the twostrains in growing on the hosts and, particularly, a higher rate of growth of bothstrains on the susceptible variety vs. tolerant one. It is known that, among the broadrange of defence responses activated in planta when Fusarium invasion occurs, thegeneration of reactive oxygen species (ROS), such as H2O2, is one of the earliestevents. The activities of three antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) correlated to ROS and of one more enzyme related tothe defensive response (lipoxygenase), were monitored to give some explanationon the different behaviour of the two wheat varieties in front of F. graminearumcontamination.Moreover, the expression of different genes activated in the interaction by arelative RT-PCR approach was analysed. In the pathogen, these genes encode for thetranscription factor Fgap1 active in the cell defence against oxidative stress, ePGa polygalacturonase involved in cell degradation and tri6, one of the thricotecenesbiosynthesis regulator. In T. aestivum, the expression analysis of a glucosyl transferase(gt) and of the pathogenesis-related protein PR1 (PR1) were carried out. The first genecan be related to a biochemical mechanism of resistance to DON with the ability toconvert DON in a less toxic glucosylated form (Lemmens et al., 2005).Finally, quantitative detection by HPLC of DON, 3GDON, 3-ADON and15-ADON produced from Fusarium species present on samples, was described. Inaddition to DON, some F. graminearum strains may also produce modified forms ofDON called 3-acetyl DON (3-ADON) and 15-acetyl DON (15-ADON).In conclusion, as far as fungal diseases are wide diffused, the control ofcontaminated matrices it’s a priority. Thus, it’s very important to deepen studies ofplant-pathogen interactions, in order to develop control strategies (i.e. quantitative,specie-specific methods) to be applied in diagnostics (i.e. advanced analytical methodfor mycotoxin detection).