Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/8/2001
Publication Date: N/A
Technical Abstract: As a first step in characterizing the role deoxynivalenol (DON) plays in pathogenesis of Fusarium graminearum in leaf and head tissues, we treated detached barley leaf tissues with DON and examined them daily for signs of injury or other alterations. As shown here, DON had pronounced and unexpected effects on leaf pigmentation at DON concentrations that were not usually lethal. DON was used at concentrations of 10-100 ppm at steps of 10 ppm. Within 3-4 days, the segments changed color in three different ways depending on DON concentration: 1) At 10-30 ppm, tissues turned light reddish brown while retaining a green background comparable to the green of control segments floated on water. In darkness, the brown color did not develop. 2) At 50-70 ppm, most tissues turned white, losing all chlorophyll and carotenoid pigments. In darkness, this loss of pigment did not occur. 3) At 80-100 ppm, the leaf segments usually remained dark green, in stark contrast to the white segments at lower DON concentrations. At 4-5 days after treatment, the segments remained as green as they were at the time of treatment. The green color was retained in either darkness or light. Control segments floated on water generally became chlorotic by 4-5 days, the usual senescence response of barley leaf tissues to detachment from plants. Because DON inhibits protein synthesis by binding to ribosomes, we speculate that chloroplast ribosomes may be highly sensitive to DON, leading to inhibition of chlorophyll and carotene synthesis at concentrations that don't affect cytoplasmic ribosomes. In any case, the present results suggest that pigment alteration in barley heads infected by Fusarium graminearum may be a consequence of pathogen-produced DON at concentrations that do not induce plant cell death.