|Perkins Veazie, Penelope|
Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2003
Publication Date: 1/13/2004
Citation: Bushnell, W.R., Seeland, T.M., Perkins Veazie, P.M., Krueger, D.E., Collins, J.K., Russo, V.M. 2003. Calciumions increase toxicity of deoxynivalenol to barley leaf tissues. In: Proceedings of the 2003 National Fusarium Head Blight Forum, December 13-15. Bloomington, Minnesota. p. 123. Interpretive Summary:
Technical Abstract: Deoxynivalenol (DON) had a bleaching effect on detached barley leaf segments (Bushnell et al, Phytopathology 92:S11, 2002). Leaf tissues lost pigmentation after incubation with 30-200 ppm DON for 2-4 days in light. The bleaching was accompanied by disorganization of chloroplasts and other cytoplasmic organelles as viewed by transmission electron microscopy (TEM). However, results were inconsistent; some segments were completely bleached, some developed only white spots or streaks, and others remained entirely green, even at high DON concentrations (90-200 ppm). Here we report that toxicity of DON is increased and tissue responses are more consistent when Ca2+ is added. The abaxial epidermis was partially stripped from detached primary barley leaf segments (1.2cm long) and the segments were then floated with exposed mesophyll in contact with DON solutions, with or without added 10mM Ca2+ (applied as Ca(NO3)2). Segments were incubated at 25oC in light (250 micromol/m2/sec). With Ca2+, DON at 10-30 ppm gave white spots or streaks by 24 hr and usually turned entire tissues white by 72 hr. Compared to treatments without Ca2+, the loss of pigment with Ca2+ occurred 1-2 days earlier, was more complete in individual segments, and was more consistent among segments. In line with this, amounts of chlorophyll and carotenoid pigments, as measured spectrophotometrically, were reduced more with Ca2+ than without. As viewed by TEM, chloroplast degeneration was underway after 18 hr of treatment with 30 ppm DON (with Ca2+) and nearly complete by 24 hr. Increased toxicity could be accounted for by greater concentration of DON within leaf segments treated with DON + Ca2+. Without Ca2+, tissues contained 3 ppm DON; with Ca2+ they contained 14 ppm DON (after 48 hr incubation in light on 30 ppm DON). Experiments are in progress to evaluate the effect of Ca2+ on DON-treated tissues incubated in the dark. The pronounced increase in toxicity of DON in present experiments suggests that Ca2+ concentrations within plant tissues may influence the effect of DON in the development of Fusarium head blight.