EFFECT OF DEOXYNIVALENOL-PRODUCING FUSARIUM GRAMINEARUM STRAINS ON SEEDS OF TOLERANT AND SUSCEPTIBLE TRITICUM AESTIVUM VARIETIES

To shorten the screening of wheat varieties tolerant to Fusarium head blight (FHB) and to deoxynivalenol (DON) synthesis the development of rapid and reliable assays is required. In this work, active but ungerminated seeds of two Triticum aestivum varieties, Blasco and Sagittario, respectively tolerant and susceptible to FHB, were inoculated with two F. graminearum strains (Fg126 and Fg8308), having a different toxigenic profile. Wheat seeds reacted to F. graminearum infection by early production of reactive oxygen species (ROS) and activating antioxidant enzymes. Whilst cv. Blasco showed an important antioxidant reaction which apparently lead to a marked decrease in ROS content, cv. Sagittario partly missed this counteraction. Compared to cv. Blasco, cv. Sagittario also produced more 9-hydroxyoctadecenoic acid (9- HODE), considered a susceptibility factor toward mycotoxigenic fungi. Moreover, some genes related to fungal aggressiveness were up-regulated in Fg126 when grown on susceptible wheat seeds and some plant defence genes advanced their expression into cv. Blasco as compared with cv. Sagittario. Finally, it turned out that DON production may trigger apoptosis, occurring very quickly after fungal inoculation and with the typical formation of pre-apoptotic vesicles into aleuronic cells. As a matter of fact, wheat seeds, irrespective of the variety, are able to partly (5-10%) convert DON in its less toxic glucosylated form (3-Glu-DON). Each of these parameters might be considered as a wheat tolerance marker and used for diagnostic purposes or, through a forward genetic approach, for selecting wheat varieties hampering DON biosynthesis.