The Toxins of Helminthosporium maydis (Race T) : A Colorimetric Determination of the Toxins, Their Appearance in Culture and in Infected Plants

Karr, D.B.; Karr, A.L.; Strobel, G.A.

Plant Physiology 55(4): 727-730

1975


ISSN/ISBN: 0032-0889
PMID: 16659155
DOI: 10.1104/pp.55.4.727
Accession: 000247173

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Abstract
Host specific toxins produced by H. maydis [Cochliobolus heterostrophus] race T [RPP 53, 4797] are measured quantitatively by a procedure involving reaction with sulphuric acid acetic anhydride reagent and measurement of the absorbance of the product at 330 nm. Total toxin concs. could be assayed after only limited fractionation of the culture medium. The highest amount of toxin/g mycelium occurs early in the growth cycle of the fungus. Toxins I, II and V are predominant at this stage both in culture and in infected maize and wheat. Some chromatographic and spectral properties of the previously unreported toxin V are described. Since it appears in culture prior to toxins I-IV, a precursor-product relationship can be suggested. Using a chemical-assay procedure involving reaction of the toxins with a sulphuric acid - acetic anhydride reagent and measurement of the absorbance of the product at 330 nm, it was shown that the highest amount of toxin per gram of mycelium occurs early in the growth cycle of Cochliobolus heterostrophus. Toxins I, II and V were the predominant toxins at these early times both in culture and in the maize variety W64A and the wheat varieties Fortuna and Manitou. Fortuna was susceptible and Manitou resistant.