FLUORESCENCE PROTEIN-TAGGED FUSARIUM GRAMINEARUM ON WHEAT AND BARLEY SPIKES

Fusarium head blight (FHB), mainly caused by Fusarium graminearum , is a very serious disease in wheat and barley production area. FHB epidemics cause yield decreases and production of mycotoxin that renders the grain useless for flour and malt products. Understanding the infection mechanism of F. graminearum plays an important role for the disease control. In present study, green fluorescence protein (GFP)-tagged were infected to wheat and barley varieties by single floret injection and screened via GFP signal. Results showed similar infection pattern of F. graminearum on both wheat and barley. Pathogen geminated in the inoculated spikelets, grew on the top of ovary or between lemma and palea, and extended towards and through rachis to the adjacent spikelets to infect the whole spike. When a spike of cultivar with FHB resistance was inoculated by F. graminearum , only the injected spikelet showed symptom at 6 days past inoculation (dpi). GFP signals indicated that F. graminearum colonized only in the inoculated spikelet and stop at the compact tissue of rachilla at 6 dpi. On the contrary, the diseased spikelets were up to 5 at 6 dpi in the spike of cultivars susceptible to FHB. F. graminearum extended through compact tissue to rachis and infected to the adjacent spikelets by spreading upward and downward to adjacent florets inter- and intra- cellularly in vascular bundles and cortical tissue of the rachis.