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Ascochyta chrysanthemi Toxin: Purification and Partial Characterization. D. L. Schadler, Former National Science Foundation Graduate Trainee, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; D. F. Bateman, Professor and Chairman, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 65:912-917. Accepted for publication 24 March 1975. DOI: 10.1094/Phyto-65-912.

Ascochyta chrysanthemi (AC) toxin was purified from 14-day-old culture filtrates of Ascochyta chrysanthemi isolate L.I.-1 by sorption and desorption from activated carbon, precipitation of nontoxic material with methanol, anion exchange chromatography, paper chromatography, and gel filtration. AC toxin is soluble in water, slightly soluble in amyl alcohol, and insoluble in other organic solvents with dielectric constants from 1.9 to 32.6. On paper chromatograms, AC toxin reacted with iodine vapor and with ammonical silver nitrate, but not with reagents used to detect free monosaccharides, amino acids, organic acids, pyrimidine reduction products, phenols, nitrophenols, or indoles. During paper chromatography, AC toxin is mobile in aqueous and acidic solvents; it is not retained during anion exchange chromatography in Tris [tris(hydroxymethyl)-aminomethane-HCl] buffer at pH 8.0, but is retained in boric acid-sodium borate buffer at pH 8.0. Upon gel filtration in Bio-Gel P-2, fractions containing AC toxin gave a positive test for carbohydrate and a negative test for free reducing groups. The only sugar detected in hydrolyzed AC toxin was mannose. AC toxin was not inactivated by tetranitromethane or by sodium borohydride, but was inactivated by periodate and by hydrolysis with trifluoroacetic acid. Infrared spectra of AC toxin had many characteristics in common with spectra of mannose; AC toxin did not absorb light between 200-450 nm. AC toxin appears to be a low-molecular-weight mannoside. The nature of the aglycone remains to be determined.

Additional keywords: Mycosphaerella ligulicola, Ascochyta blight of florist's chrysanthemum, mannoside.