Submitted to: North American Barley Research Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Technical Abstract: We are investigating development of Fusarium graminearum on and in barley florets and other organs using a transformed strain of the fungus containing a gene for green fluorescent protein (GFP). To remove surface mycelium which can obscure fungus development within underlying tissues, a 2 to 1 (v/v) solution of cellulose acetate in acetone is applied to the tissue surface, allowed to dry for a few minutes, then stripped away, leaving the tissue surface intact and free of mycelium. In initial experiments, inoculum in the form of mycelium growing on mung bean agar blocks (2x12x0.5 mm) was applied to cut ends of detached leaves, coleoptiles, the palea, and the lemma from Robust (susceptible) and Chevron (partially resistant) barley. The fungus grew both into and on top of the inoculated tissues. By three days after inoculation, hyphae within tissues grew 2.9-3.1 mm in leaves, 1.2 - 1.5 mm in coleoptiles and paleae, but less sthan 0.2 mm in lemmae (as measured from the cut ends to the advancing hyphal front). In leaves, the distance was increased to 4.5 - 5.3 mm if the inoculum block was left in place 48 hr instead of 24 hr. Hyphae within tissues were subcuticular and intercellular. Hyphae appeared to grow into and out of leaf stomates. The results show that fungus development was limited in paleae, lemmae and coleoptiles compared to development in leaves, that exogenous nutrients can increase amount of colonization in leaves, and that development was the same in tissues of Robust and Chevron.