Submitted to: North American Barley Research Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/22/2002
Publication Date: N/A
Technical Abstract: From histological observations of diseased tissues, we postulate that deoxynivalenol (DON) contributes to the necrotrophic phase of Fusarium head blight development. As a first step toward understanding effects of DON, we are using uninfected barley leaf segments to assess cytological and physiological effects of the toxin on green tissues. We partially stripped the abaxial epidermis from detached Robust leaf segments (1.2 cm long) and floated them with stripped mesophyll in contact with aqueous DON solutions at 30-200 ppm. When incubated in light (150-450 micro mol/m**2/sec), tissues on DON (at all tested concentrations) usually turned white within 48-72 hr from loss of chlorophyll and carotenoid pigments. In darkness, DON-treated tissues remained green. As viewed by transmission electron microscopy, DON induced a characteristic increase in spacing of thylakoid chloroplast membranes in light, but not in darkness. In both light and dark, however, DON markedly increased loss of electrolytes from tissues as measured by electrical conductivity of incubating solutions. This indicates that DON had a detrimental effect on plant cell plasma membranes, causing loss of electrolytes. In summary, DON in leaves mimicked effects of Fusarium head blight in heads by causing loss of chloroplast pigments (although only in the light) and by causing other degenerative changes (in light and dark). The results support the hypothesis that DON toxicity has a role in pathogenesis.