A quantitative bioassay for necrosis toxin from Pyrenophora tritici-repentis based on electrolyte leakage

• Published in: Phytopathology Vol. 86; no. 12; pp. 1360 - 1363
• Main Authors: Kwon, C.Y. (North Dakota State University, Fargo.), Rasmussen, J.B, Francl, L.J, Meinhardt, S.W
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 01-12-1996
• Subjects: AGENT PATHOGENE; Biological and medical sciences; CONDUCTIVIDAD ELECTRICA; CONDUCTIVITE ELECTRIQUE; DIFERENCIAS BIOLOGICAS; DIFFERENCE BIOLOGIQUE; DOSAGE BIOLOGIQUE; DURACION; DUREE; ELECTROLITOS; ELECTROLYTE; ENFERMEDADES FUNGOSAS; ENSAYO BIOLOGICO; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Generalities. Techniques; LESSIVAGE DU SOL; LIXIVIACION; MALADIE FONGIQUE; MICOTOXINAS; Microbiology; Mycological methods and techniques used in mycology; Mycology; MYCOTOXINE; ORGANISMOS PATOGENOS; PERDIDAS; PERTE; Phytopathology. Animal pests. Plant and forest protection; PLANTULAS; PLANTULE; PYRENOPHORA TRITICI-REPENTIS; TEMPERATURA; TEMPERATURE; TRITICUM AESTIVUM; VARIEDADES; VARIETE; Monocotyledones; Bioassay; Mycotoxin; Method; Cereal crop; Fungi; Assay; Toxin; Gramineae; Angiospermae; Pyrenophora tritici-repentis; Electrolyte leakage; Ascomycetes; Spermatophyta; Triticum aestivum; Thallophyta
• ISSN: 0031-949X; 1943-7684

Pyrenophora tritici-repentis, the causal agent of tan spot of wheat, produces a cultivar-specific toxin (Ptr necrosis toxin) closely associated with the disease symptomatology. We initiated studies aimed at the mode-of-action of Ptr necrosis toxin and, as a first step, report here a bioassay for toxin based on electrolyte leakage. Toxin exposures of 4 h or more caused enhanced electrolyte leakage from wheat line ND495 (toxin sensitive), but not cv. Erik (toxin insensitive), relative to water-treated controls. Electrolyte leakage increased with exposure times up to 12 h the longest time tested, when toxin concentration and leaching time were held constant. Electrolyte leakage increased with toxin concentration between 1 and 20 microgram ml-1, when exposure and leaching times were constant. All toxin-sensitive wheats tested (based on toxin-induced necrosis) showed enhanced electrolyte leakage, and all insensitive wheats did not. A toxin exposure of 4 h permitted completion of the assay in 1 day. We used this rapid assay to demonstrate that incubation of ND495 seedlings at 30 degrees C for 24 h prior to toxin exposure causes a loss of toxin sensitivity. Enhanced electrolyte leakage is the most rapid response to toxin observed to date. However, the toxin exposure times required for leakage to develop (4 h or longer) suggest that effects on the plasmalemma are secondary and occur relatively late in the development of necrosis