Isolation and identification of a phytoalexin from sugarcane
Brinker, Anita Marie
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Permalink
https://hdl.handle.net/2142/22082
Description
Title
Isolation and identification of a phytoalexin from sugarcane
Author(s)
Brinker, Anita Marie
Issue Date
1990
Doctoral Committee Chair(s)
Seigler, David S.
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Botany
Agriculture, Plant Pathology
Language
eng
Abstract
Literature reports concerning the sugarcane disease, red rot (causal agent Colletotrichum falcatum Went; teleomorph Glomerella tucumanensis (Speg.) von Arx and E. Muller), indicate that disease resistance is associated with production of a red material. This red substance accumulates in sugarcane (Saccharum spp.) cells infected by or adjacent to hyphae of C. falcatum, and appears to inhibit further hyphal growth. Resistant sugarcane cultivars reportedly produce the red material more quickly after infection than susceptible cultivars. Previous workers had identified luteolinidin, an anthocyanidin, in extracts of infected sugarcane and suggested that the compound was a phytoalexin. However, the role of this compound was not unambiguously established. This study was undertaken to determine whether sugarcane produces phytoalexins of other chemical classes.
Sugarcane stalks inoculated with C. falcatum spore suspension were extracted after an incubation period. Ethyl acetate washes of these extracts inhibited germination of C. falcatum spores. The corresponding washes from sugarcane stalks that were wounded but not inoculated, or that were neither wounded nor inoculated, were not inhibitory. Two-dimensional paper chromatography revealed that 20-30 compounds accumulated in inoculated cane but not in cane that was only wounded. A fungitoxic compound was isolated from extracts of inoculated cane by droplet countercurrent chromatography and thin layer chromatography. The compound was identified as piceatannol by comparison of its UV, $\sp1$H and $\sp{13}$C NMR, and mass spectra with spectra from the literature and from a sample of synthetic piceatannol. The ED$\sb{50}$ of piceatannol is about 7 ppm for C. falcatum germ tube growth and about 50 ppm for spore germination. Piceatannol was not present in uninoculated sugarcane and was not induced by wounding alone. It also was not detected in sugarcane suspension cultures. In inoculated cane piceatannol was first detected 2-3 days after inoculation and reached maximum levels 6 days after inoculation. Within 4 days after inoculation the piceatannol concentration was above that necessary to completely inhibit C. falcatum germ tube growth in vitro. It appears that piceatannol is a phytoalexin in sugarcane and is present in sufficient amounts in infected tissues to play a role in resistance to red rot.
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