Ptr necrosis toxin, a cultivar-specific toxin produced by Pyrenophora tritici-repentis, has been closely associated with the symptomatology of tan spot of wheat. We have developed a rapid quantitative bioassay for Ptr necrosis toxin based on electrolyte leakage. All toxin- sensitive wheat lines (based on necrosis development during a 72-h incubation with toxin) showed enhanced electrolyte leakage in response to toxin relative to water controls, whereas all toxin- insensitive wheats did not. The magnitude of leakage increased with toxin concentration under standard assay conditions. A 4-h toxin exposure permitted completion of the assay in one day. The electrolyte leakage bioassay has been used to demonstrate that toxin action is temperature sensitive in the host. Other experiments with the assay indicate that toxin action requires host metabolism, including ATP-utilizing proton pumps, protein synthesis, and putative signaling mechanisms.

English

9806|AGRIS 9802

Jose Juan Caballero

CIMMYT Publications Collection