STEM-TO-HEAD COLONIZATION BY THREE FUSARIUM SPECIES AND DEOXYNIVALENOL TRASLOCATION IN BARLEY (Hordeum vulgare L.).

Fusarium crown rot (FCR) is an important disease of wheat and barley mainly caused by Fusarium graminearum, F. pseudograminearum and F. culmorum, which are also responsible for the production of the mycotoxin deoxynivalenol (DON) during plant colonization. While most of studies on fungal colonization are focused on wheat, this is the first investigation on the colonization process of barley by these pathogens. The three above mentioned species were inoculated at the stem base level. At maturity, symptoms were visually evaluated and then plants were cut into four segments: Segment 1 (the area adjacent to the crown, including the first node) Segment 2 (the area including the second node) Segment 3 (the area adjacent to the flag leaf) and Segment 4 (head). Fungal DNA quantification of each inoculated strain was performed, on each segment, by Real Time qPCR. DON presence along the plant was determined by ELISA method. All inoculated strains caused browning, symptom particularly evident up to the second node, and the F. culmorum strain seemed to be the most virulent. Real Time qPCR assays showed that both F. graminearum and F. culmorum DNA was found up to the head, while F. pseudograminearum DNA was found up to the second node. For every pathogens, DON was detected up to the head. This study shows that barley, as already demonstrated in wheat, may be subject to head contamination by DON produced during FCR, thus representing a DON source in addition to Fusarium head blight contaminations.